**INHALTE**

#### Research Training Group

**Lorentz Force Velocimetry and Lorentz Force Eddy Current Testing**

# Archive Guest Lecture

# 2018

### 06 Dec 2018, Electroerosion dispersion, sorption and coagulaton for complex water purification; electroerosion waste recycling and manufacturing of metals, oxides and alloys nanopowders

Ms. Prof. Dr. T. Prikhna

V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine

Department of Technologies of superhigh pressures, functional structured ceramic composites and dispersed nanomaterials

**Electroerosion dispersion, sorption and coagulaton for complex water purification; electroerosion waste recycling and manufacturing of metals, oxides and alloys nanopowders**

**Abstract:**

The application of EDSC - electroerosion dispersion, sorption and coagulation (using in-situ dispersion in plasma of aluminium or iron) allowed efficient water purification from heavy metal ions and radioactive alkali ions (of Fe, Cr, Cu, Mo, Zn, Co, Ni, Cd, Mn, As, Sn, Pb, Al, Ba, Co, Cs and Sr) as well as from organic contaminations. While for water cleaning from the «heavy» organic contaminations (such as liquid waste of landfills) the intensive ozonization should be applied because of intensive foam formation as a result of complex electro-hydrodynamic effect during EDSC. The method of electroerosion dispersion is very effective for production of nano- and submicron powders (5 nm – 3 µm) of metals, oxides, nitrides and carbides as well as for recycling of any conductive materials such as cemented carbides, alloys of heavy metals, any metallic waste products etc. The iron oxide polyvalent magnetic nanoparticles produced by electroerosion dispersion have considerable interest in many fields of research and application due to their attractive properties. They have high potential for applications in the field of biomedical sciences (diagnostics and therapy), ferrofluids, catalysis, colored pigments, high-density magnetic recording, printer toners, Li-ion batteries, wastewater treatment and absorption of electromagnetic waves.

### 29 Nov 2018, The experimental investigations on liquid metal MHD heat transfer applied to fusion reactors / Temperature fluctuations in a heated horizontal tube affected by transverse magnetic field

Prof. V.G. Sviridov

Moscow Power Engineering Institute, Technical University,

Department of Engineering Thermophysics

**The experimental investigations on liquid metal MHD heat transfer applied to fusion reactors**

**Abstract:**

The talk is about MPEI JIHT activities in the field of liquid metal investigations of hydrodynamics and heat transfer affected by longitudinal and transverse magnetic field. Current experiments program deals with temperature and velocity fields, local and average heat transfer intensities, temperature fluctuation intensities in a horizontal heated tube. The strong influence of thermo gravitational convection in all regimes was observed in experiments applied to blanket and divertor of tokamak. Two unexpected troubles were discovered: zones of extremely low local heat transfer intensities in some regimes of magnetic field and thermogravitation joint influence; dangerous temperature low-frequent fluctuations with high amplitude near the tube wall in some magneto hydrodynamic configurations with buoyancy affect. Numerical simulation of magneto hydrodynamic heat transfer is working out simultaneously with experiments.

Dr. Ya.I. Listratov

Moscow Power Engineering Institute, Technical University,

Department of Engineering Thermophysics

**Temperature fluctuations in a heated horizontal tube affected by transverse magnetic field**

**Abstract:**

It is widely accepted that a sufficiently strong constant magnetic field suppresses fluctuations of velocity and, therefore, of temperature. It has, however, been found in experimental investigations that dangerous low-frequency and high-amplitude temperature fluctuations may appear near the tube walls in some configurations due to the thermo gravitational convection effect. Detailed investigation of flow in nonuniformly heated horizontal pipe affected by transverse magnetic field is the topic of the talk. The results of experimental and numerical investigations of the MHD heat transfer are presented revealing nature of the phenomenon.

### 04 Oct 2018, Droplet and Particle Technologies for Chemistry and Physics

Professor Steve Wereley

Mechanical Engineering, Purdue University

**Droplet and Particle Technologies for Chemistry and Physics**

**Abstract:**

Recently Prof. Wereleys research group in the Microfluidics Laboratory at Purdue University has developed several innovative technologies with potential applications in the bio/medical/chemical/pharma industries. These are (1) droplet-based microfluidics, (2) opto/electric droplet manipulation, and (3) opto/electric particle manipulation and (4) particle diffusometry. During the presentation Prof. Wereley will present the fundamental principles behind these methods, what their capabilities are, and what their potential uses are. The talk will review:

On-chip methods of pumping, mixing, and combinatorial chemistry. The most exciting recent development is the ability to produce a sequence of hundreds of droplets with a gradient of a desired compound. This technology is quite useful for constructing dose/response curves while consuming a minimum of potentially expensive samples and reagents as well as for minimizing human or even robotic involvement in constructing dose/response curves.*Droplet-based microfluidics:*using lasers and electric fields the control and manipulation of individual droplets is possible which helps to perform assays and other chemical operations. This method is similar to opto-electrowetting (OEW or EWOD) except that the “electrodes” used for the droplet manipulation are virtual electrodes whose locations are defined by dynamic laser light patterns rather than fixed, unmovable conventional electrodes.*Opto/electric droplet manipulation:*using lasers and electric fields micro- and nanometer-scaled “particles” can be concentrated, manipulated and sorted. The “particles” range in size from single molecules (DNA, proteins, etc.) to nanoparticles (quantum dots, carbon nanotubes, nano-scaled polystyrene latex beads, etc.) to biological organisms (bacteria, mammalian cells, etc.). This novel technique combines features of optical trapping (OT) and dielectrophoresis (DEP) in an innovative, dynamic way using a simple parallel plate electrode configuration. Applications range from collecting desired cell populations to separating one size of particle from another.**Opto/electric particle manipulation:**Through the Stokes-Einstein diffusion coefficient and the statistics of PIV, the effective hydrodynamic diameter of the particle increasing due to surface adhesion as well as viscosity increase due to rheology changes of the suspension can be measured. As an example the degradation of insulin, a commonly used protein for patients with diabetes is considered and intact insulin can be discriminated from degraded samples.**Particle Diffusometry:**

**Bio:**

Professor Wereley completed his masters and doctoral research at Northwestern University. He joined the Purdue University faculty in August of 1999 after a two-year postdoctoral appointment at the University of California Santa Barbara. During his time at UCSB he worked with a group developing, patenting, and licensing to TSI, Inc., the micro-Particle Image Velocimetry technique. His current research interests include designing and testing microfluidic MEMS devices, investigating biological flows at the cellular level, improving micro-scale laminar mixing, and developing new micro/nano flow diagnostic techniques. Although considerably outside the field of microfluidics, Professor Wereley used his flow measurement expertise to analyze the Deepwater Horizon oil spill in the Gulf of Mexico in 2010, serving on the US government’s Flow Rate Technical Group. His contributions to characterizing the disaster were recognized with the US Geological Survey Director’s Award. Professor Wereley is the co-author Particle Image Velocimetry: A Practical Guide, 3^{rd} ed (Springer, 2018). He is on the editorial board of Experiments in Fluids and is an Associate Editor of Springer’s Microfluidics and Nanofluidics. Professor Wereley has edited Springer’s recent Encyclopedia of Microfluidics and Nanofluidics and Kluwer’s BioMEMS and Biomedical Nanotechnology.

### 06 August 2018, An Active Set Algorithm for Robust Combinatorial Optimization Based on Separation Oracles

Prof. Marianna De Santis

Sapienza Università di Roma

**An Active Set Algorithm for Robust Combinatorial Optimization Based on Separation Oracles**

**Abstract:**

In the context of robust combinatorial problems, we propose a branch-and-bound algorithm based on the solution of the Lagrangian dual of relaxations built using a separation oracle.

Namely, we assume that the set of feasible solutions is given by a separation algorithm that decides whether a given point belongs to the convex hull of the feasible set or not, and, in the negative case, provides a valid inequality.

At every node of our branch-and-bound, we solve the Lagrangian dual by a feasible active set method, devised on purpose. The method beneﬁts from the closed form solution of speciﬁc subproblems and a smart update of pseudo-inverse matrices.

We present numerical experiments on randomly generated instances and on instances from diﬀerent combinatorial problems, including the shortest path and the traveling salesman problem, showing that our new algorithm consistently outperforms the state-of-the art mixed-integer SOCP solver of Gurobi.

### 26 June 2018, Instabilities of Helical Vortices

Dr. Maurice Rossi

Institut Jean Le Rond D'Alembert IJLRA

Université de Paris

**Instabilities of Helical Vortices**

**Abstract:**

After a general introduction on vortex dynamics, I shall present the dynamics of helical vortices observed behind propellers, wind turbine or helicopters.

This problem has been tackled via a DNS approach based on a dedicated code.

It is shown that the helical vortices share features with both straight vortices and vortex rings.

### 05 June 2018, Recent studies on liquid metal film/droplet under the influence of horizontal magnetic field

Prof. Juan-cheng Yang

School of Aerospace

Xi'an Jiaotong University, P.R. China

**Recent studies on liquid metal film/droplet under the influence of horizontal magnetic field**

**Abstract:**

In the lecture, I’ll give an overview of the experimental studies on liquid metal in our group in China. It contains the liquid GaInSn film flow, liquid lithium film flow and the liquid GaInSn droplet spreading with the influence of horizontal magnetic field up to 2T. As for the part of liquid metal film flow, experimental results show that the spanwise direction magnetic field plays an important role in the regularization of film surface waves, namely when gradually increasing the strength of magnetic field, the random surface waves can be firstly damped along the direction of magnetic field and then strongly inhibited due to the induced Lorentz force. The decreasing of wave velocity also indicates that the spanwise magnetic field has a stabilizing effect on The film flow. As for the part of droplet spreading on solid surface, we experimentally observed the elliptical spreading phenomenon of liquid metal droplet with the influence of horizontal magnetic field.

### 08 May 2018, Adjoint-based optimization of a complete design chain in CFD

Prof. Andrea Walther

Universität Paderborn

**Adjoint-based optimization of a complete design chain in CFD**

**Abstract:**

The complete design chain in Computational Fluid Dynamics (CFD) covers the parameterization of the object to be optimized like, e.g., an air foil, the usage of a Computer Aided Design (CAD) tool to actually construct the air foil and a flow solver to compute the flow around the air foil. The optimization of such a complete design chain that includes a CAD tool is still a severe challenge due to lacking derivative information. In this talk we present the technique of algorithmic differentiation (AD) to compute exact derivative information for a given simulation code. We discuss how AD can be applied to the CAD kernel within OpenCASCADE Technology and a suitable flow solver taking also the complexity of the derivative information into account.

We will see that a gradient-based optimization using adjoint information is the only tractable way. First numerical results for the optimization of a U-bend pipe used frequently as a cooling channel and of the TU Berlin stator as one example from turbo machinery are shown. This includes also a verification of the computed derivatives.

### 17 April 2018, Tunable Loop-Based Microfluidics Pumped by Redox-Magnetohydrodynamics: Toward Miniaturized Technologies for Chemical Analysis

Prof. Ingrid Fritsch

Department of Chemistry and Biochemistry

University of Arkansas

**Tunable Loop-Based Microfluidics Pumped by Redox-Magnetohydrodynamics: Toward Miniaturized Technologies for Chemical Analysis **

**Abstract:**

Pumping liquids on a small scale in an automated fashion is important for sample processing and manipulation within micro total analysis systems (µTAS) for point of care, environmental, and chemical synthesis applications. The ability to pump fluid not only in a straight line, but also in a loop expands the possible functions of µTAS. This is especially challenging for traditional micropump approaches, which require complicated algorithms and/or check valves to achieve this goal. Redox-magnetohydrodynamics (R-MHD) can address this need. R-MHD drives fluid through a body force,** F _{B}**, governed by the cross product of ionic current density,

**j**, and a magnetic field,

**B**. The

**B**can be obtained from a simple permanent magnet. The

**j**can be generated by individually-addressable microelectrodes, patterned on a chip in different geometries and dimensions, that can be activated by applying various potentials or currents. Therefore, the direction and speed of fluid flow is essentially programmable. The presentation will examine R-MHD in aqueous solutions using diverse configurations of disk and concentric ring electrodes of various radii under different conditions. The discussion will include stirring and mixing under laminar flow conditions and opportunities for continuous chemical separations in a cyclical design.

### 10 April 2018, Industrial applications of electromagnetic stirring: optimization aspects

Dr. Diana Köppen

Institut für Elektroprozesstechnik

Universität Hannover

**Industrial applications of electromagnetic stirring: optimization aspects**

**Abstract:**

In the lecture the most promising methods of electromagnetic (EM) processing of liquid metals will be considered. Magnetohydrodynamic processes, taking place in the industrial equipment, are going to be discussed. The base industrial applications of EM stirring are going to be analyzed from the point of view of their optimization. As well, a new and rapidly developing method, allowing the visualization of melt flow and solidification process, influenced by EM field is going to be presented and discussed.

### 21 March 2018, HTS bulk magnets as very compact and strong magnetic field generators

Prof. Tetsuo OKA

Niigata University, Japan

**HTS bulk magnets as very compact and strong magnetic field generators**

**Abstract:**

Various types of strong magnetic field generators with use of HTS bulk magnets and the small-scale refrigerators have been actually proposed and experimentally estimated for the feasible applications. The most characteristic feature of bulk magnets is regarded as compact and strong field generators with respect to their magnetic field spaces or their machine structures of themselves. Among them, the magnetic flux density of the face-to-face magnetic poles reached 3.2 T and 4.4 T when they were activated by the pulsed field magnetization and the field cooling method, respectively. Although the bulk magnets are characterized by their steep field distributions, we attempted to gain the uniform magnetic field space, and successfully achieved the uniformity of 385 ppm in 4 mm range by combining the deformed magnetic field profiles which generated between the face-to-face magnetic poles. The performances of these unique systems have exceeded those of the conventional electromagnet or any permanent magnets, demonstrating the superiority to other strong magnetic field generators.

# 2017

### 19 Dec 2017, Recent developments on inductive measurement techniques for liquid metals

Dr. Thomas Wondrak

Helmholtz-Zentrum Dresden-Rossendorf

**Recent developments on inductive measurement techniques for liquid metals**

**Abstract:**

There is a growing interest in determining the flow properties of metal or semiconductor melts, such as flow rate, flow structure and gas distribution. Typical applications are melt refining, continuous steel casting, silicon crystal growth or cooling of the receiver of a concentrated solar thermal power plant. However, the opaqueness prevents the use of well established optical methods. Additionally, the high temperatures (e. g. 1500°C for liquid steel or liquid silicon) and the corrosiveness of those fluids demand for contactless measurement techniques. By exploiting the high electrical conductivity of those melts inductive methods can be used. In this talk several inductive measurement techniques will be presented including transient eddy current flow meter, contactless inductive flow tomography and mutual inductance tomography. Additionally, a short overview about ultrasound techniques will be given which can be used to verify the inductive methods.

### 23 Nov 2017, Optimization of Pumping by Redox-Magnetohydrodynamics (R-MHD) for Micro Total Analysis Systems

Foysal Z. Khan

Department of Chemistry and Biochemistry

University of Arkansas, Fayetteville, AR 72701 USA

**Optimization of Pumping by Redox-Magnetohydrodynamics (R-MHD) for Micro Total Analysis Systems**

**Abstract:**

Redox-Magnetohydrodynamics (R-MHD) is a phenomenon where fluid moves by a net body force **(FB)** and is governed by the equation **F _{B} = j × B**. In our studies,

**j**is the ionic current density through an aqueous, unreactive buffer or electrolyte, produced from redox reactions of conducting polymer, and driven by applying current or potential at the underlying microelectrodes on a chip. The

**B**is the magnetic flux density generated either from permanent or electro- magnets. The presentation will describe optimization of electrodeposition conditions for immobilizing poly(3,4-ethylenedioxythiophene) (PEDOT) to maximize charge capacity (to enhance pumping duration) and current responses (to expand the range of pumping speeds). The use of electrodes modified with the optimized conducting polymer will also be discussed. This includes fundamental investigations of on-chip fluid flow profiles and device development for bioanalytically-relevant MHD applications. For example, in collaboration with Tim Muldoon in the Biomedical Engineering department, we have merged the flat flow profiles produced by R-MHD pumping with epitaxial light sheet confocal microscopy (e-LSCM) to realize on-chip image cytometry of white blood cells. In addition, we have advanced the R-MHD technology further to pump small volumes of physiologically-compatible fluids indefinitely in a single-direction by integration with novel strategies of manipulating the magnetic field.

**Bio-sketch:** Foysal Z. Khan is working at the University of Arkansas as a PhD student. He received his BSc (2011) and MSc (2013) in Applied Chemistry and Chemical Engineering from University of Dhaka, Bangladesh. His research focuses on materials optimization to enhance R-MHD pumping system for µ-TAS applications.

### 22 Nov 2017, Optimisation in Space: Problems in Spacecraft Trajectory Optimization

Prof. Jörg Fliege

University of Southampton, United Kingdom

**Optimisation in Space: Problems in Spacecraft Trajectory Optimization**

**Abstract:**

In trajectory optimization, the optimal path of a flight system or a group of flight systems is searched for, often in an interplanetary setting: we are in search of trajectories for one or more spacecrafts. On the one hand, this is a well-developed field of research, in which commercial software packages are already available for various scenarios. On the other hand, the computation of such trajectories can be rather demanding, especially when low-thrust missions with long travel times (e.g., years) are considered. Such missions invariably involve gravitational slingshot maneuvers at various celestial bodies in order to save propellant or time. Moreover, maneuvers involve vastly different time scales: years of coasting can be followed by course corrections on a daily basis. In this talk, we give an overview over trajectory optimization for space vehicles and highlight some recent algorithmic developments.

### 17 Oct 2017, Convection and magnetoconvection in a rotating Tangent Cylinder

Prof. Alban Potherat

Coventry University,

United Kingdom

**Convection and magnetoconvection in a rotating Tangent Cylinder**

**Abstract:**

The liquid core of the Earth is subject to intense convection driven by the heat and solute elements released from the solid core. It drives the dyamics of the entire planet, from plate tectonics to the Earth magnetic field.

The tangent cylinder is the region of the liquid core obtained by elevating the boundary of the solid core (1200 km radius) along the Earth rotation axis, up to the the Core-Mantle Boundary (3500 km radius). Even though, it is not bounded by solid boundaries, the Taylor-Proudman constraint that results from the Coriolis force makes it difficult for the flow there to cross this imaginary boundary. As a consequence convection there behaves partly as between unbounded planes, but also a lot like in solid cylinders. Between planes, it is well known that the effect of a magnetic field, such as the Earth's can radically lower the critical Rayleigh number at which convection ignites and alter the ensuing convection patterns. Yet, it is unclear how this effect translates in these peculiar conditions.

Here we report experiments conducted in transparent sulfuric acid, where both convection and magnetoconvection could be visualised by means of some of the large magnets available at the Grenoble High Magnetic Field Laboratory. We show that the similarity between convection in a TC and in a solid cylinder is all the stronger as rotation is fast and that the picture is radically changed under the effect of an external magnetic field.

### 16 May 2017, Optimisation in Space: Problems in Spacecraft Trajectory Optimization

Prof. Jörg Fliege

University of Southampton, United Kingdom

**Optimisation in Space: Problems in Spacecraft Trajectory Optimization**

**Abstract:**

In trajectory optimization, the optimal path of a flight system or a group of flight systems is searched for, often in an interplanetary setting: we are in search of trajectories for one or more spacecrafts. On the one hand, this is a well-developed field of research, in which commercial software packages are already available for various scenarios. On the other hand, the computation of such trajectories can be rather demanding, especially when low-thrust missions with long travel times (e.g., years) are considered. Such missions invariably involve gravitational slingshot maneuvers at various celestial bodies in order to save propellant or time. Moreover, maneuvers involve vastly different time scales: years of coasting can be followed by course corrections on a daily basis. In this talk, we give an overview over trajectory optimization for space vehicles and highlight some recent algorithmic developments.

### 25 April 2017, The Design Analysis and Experimental Characterization of the MHD Pump for the Circulation of Liquid Metal Coolant

Hee Reyoung Kim, Ph. D. Associate Professor

School of Mechanical and Nuclear Engineering

Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea

**The Design Analysis and Experimental Characterization of the MHD Pump for the Circulation of Liquid Metal Coolant**

**Abstract:**

An MHD pump is a key element for the liquid metal circulation of the Intermediate Heat Transfer System (IHTS) in the Prototype GenIV Sodium Fast Reactor (PGSFR) with electric output of 150 MWe which is expected to be constructed in 2028 in Korea. An MHD pump, which has no mechanical part contacting with the liquid metal fluid of the high chemical reactivity and strong corrosiveness, is required to circulate the liquid metal coolant without particular maintenance for a long period. Its design variables are optimized from the magnetohydrodynamic and equivalent electric circuit analysis leading to design and experimental verification of the annular linear MHD pump with a flow rate of 60 L/min and a developed pressure of 1 bar. The MHD pressure drop of the liquid sodium flow is measured in the transverse magnetic field with the comparison of the theoretical calculation. Finally, suggested is the conceptual design variables of the MHD pump for the large flowrate circulation of 50,000 L/min for the future PGSFR.

### 04 April 2017, Numerical simulations of magnetohydrodynamic problems: application to dynamo action and liquid metal batteries

Prof. Caroline Nore

LIMSI Paris

**Numerical simulations of magnetohydrodynamic problems: application to dynamo action and liquid metal batteries**

in collaboration with J.-L. Guermond, J. Léorat, F. Luddens, W. Herreman, L. Cappanera and D. Castanon-Quiroz

**Abstract:**

We study the generation of magnetic fields by flows of electrically conducting fluids (called dynamo action) and the stability of liquid metal batteries using direct numerical simulations. We have been developing a so-called code SFEMaNS since 2002 [1] capable of simulating the nonlinear magnetohydrodynamic (MHD) equations in heterogeneous domains (with electrical conductivity or magnetic permeability jumps) in axisymmetric geometries and with several fluids. We present in this talk a case of dynamo action obtained in a cylindrical tank, namely a model of the von Kármán Sodium experiment (VKS), which could generate a steady or intermittent magnetic field in 2007 [2]. For the first time, the counter-rotating impellers made of soft iron are realistically modeled by means of a pseudo-penalization method and of a new algorithm based on the induction field. Our results show that using a ferromagnetic material for the impellers decreases the dynamo threshold and enhances the predominantly axisymmetric magnetic field: the resulting dynamo is a mostly axisymmetric axial dipole with an azimuthal component concentrated in the impellers as observed in the VKS experiment [3]. We will also discuss liquid metal batteries that would be less expensive than traditional batteries to store renewable energy produced intermittently and which are developed by a US start-up AMBRI [4]. We investigate a possible instability of these batteries called the Tayler instability [5].

Key words : Magnetohydrodynamics, dynamo effect, direct numerical simulation, Multiphase flows.

[1] J.-L. Guermond, J. Léorat, F. Luddens, C. Nore, and A. Ribeiro. Effects of discontinuous magnetic permeability on magnetodynamic problems. J. Comput. Phys., 230 :6299–6319, 2011.

[2] R. Monchaux, M. Berhanu, M. Bourgoin, Ph. Odier, M. Moulin, J.-F. Pinton, R. Volk, S. Fauve, N. Mordant, F. Pétrélis, A. Chiffaudel, F. Daviaud, B. Dubrulle, C. Gasquet, L. Marié, and F. Ravelet. Generation of magnetic field by a turbulent flow of liquid sodium. Phys. Rev. Lett., 98 :044502, 2007.

[3] C. Nore, D. Castanon Quiroz, L. Cappanera and J. L. Guermond : Direct numerical simulation of the axial dipolar dynamo in the von Kármán Sodium experiment. Europhysics Letters, EPL, 114, 65002, 2016.

[4] AMBRI http://www.ambri.com/

[5] W. Herreman, C. Nore, L. Cappanera and J. L. Guermond : Tayler instability in liquid metal columns and liquid metal batteries. J. Fluid Mech., vol. 771, pp. 79-114, 2015.

### 21 March 2017, Numerical simulation of superconducting materials for electric machines

Mark D. Ainslie

Department of Engineering

University of Cambridge, United Kingdom

**Numerical simulation of superconducting materials for electric machines**

**Abstract:**

The Bulk Superconductivity Group at the University of Cambridge is currently investigating the use of high temperature superconducting (HTS) materials in wire and bulk form in order to increase the electrical and magnetic loading of an axial gap, trapped flux-type superconducting electric machine. As part of this research, advanced 2D axisymmetric and 3D finite-element models of superconducting coils and bulks have been developed to investigate and simulate their electromagnetic behaviour.

In this presentation, some of our recent work on analysing the performance of HTS coils with respect to their AC (AC loss) and DC (maximum allowable current) characteristics will be highlighted, including the simulation of in-field performance [1], increasing the computational speed and accuracy of 3D models [2], and the influence of ferromagnetic materials on the performance of HTS coils [1,3,4].

I will also present a summary of some of the current state-of-the-art in modelling the magnetisation of bulk superconductors [5], including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials, which can act as strong trapped field magnets (TFMs). Such TFMs are able to trap magnetic fields greater than 17 T [6], an order of magnitude higher than the maximum field produced by conventional permanent magnets. The differences between simulating the different magnetising techniques – zero field cooling (ZFC), field cooling (FC) and pulsed field magnetisation (PFM) – will be explained, as well as the differences and similarities in the assumptions made for the numerical simulation related to bulk (RE)BCO and MgB_{2} samples.

**Fig. 1:** *A triangular, HTS pancake coil (left) and the basic structure of a 3D finite-element model developed to simulate the coil’s electromagnetic properties (right). 1/6 ^{th} of the length of the coil is modelled using symmetric boundary conditions.*

**References **

1. M. D. Ainslie et al., IEEE Trans. Appl. Supercond. 25, 4602305 (2015).

2. D. Hu, M. D. Ainslie et al., Supercond. Sci. Technol. 28, 065001 (2015).

3. M. D. Ainslie et al., Supercond. Sci. Technol. 24, 045005 (2011).

4. M. D. Ainslie et al., IEEE Trans. Appl. Supercond. 23, 4700104 (2013).

5. M. D. Ainslie, H. Fujishiro, Supercond. Sci. Technol. 28, 053002 (2015).

6. J. H. Durrell et al., Supercond. Sci. Technol. 27, 082001 (2014).

**Biography **

Mark Ainslie received the B.E. (Electrical & Electronic) & B.A. (Japanese) degree in from the University of Adelaide, Australia, in 2004, the M.Eng. degree from the University of Tokyo, Japan, in 2008, and the Ph.D. degree from the University of Cambridge, UK, in 2012. He is currently a Royal Academy of Engineering Research Fellow in the Bulk Superconductivity Group at the University of Cambridge. His research interests are in applied superconductivity in electrical engineering, including superconducting electric machine design, bulk superconductor magnetisation, numerical modelling, and interactions between conventional and superconducting materials.

### 14 March 2017, Computation of Lorentz force and 3-D eddy current distribution in translatory moving conductors in the field of a permanent magnet

Bojana Petkovic

TU Ilmenau

**Computation of Lorentz force and 3-D eddy current distribution in translatory moving conductors in the field of a permanent magnet**

**Abstract:**

Determination of the 3-D eddy current distribution inside a translatory moving conductor under a permanent magnet can accurately be done by using Finite Element Method (FEM). However, FEM calculations are very expensive, as they require discretization of the whole conductor volume. We compute 3-D eddy current and force density distribution inside conductive specimen using the Boundary Element Source Method.

Besides the weak reaction approach, the BESM does not involve any assumptions on the eddy current flow and can be applied on arbitrarily shaped specimen and defect geometries. Furthermore, the BESM can be used for determination of the induced eddy current distribution and the electric scalar potential in solid conductive materials with defects of any conductivity. Multiple defects can be considered as well and each defect can have its own conductivity. The position and orientation of a defect inside a specimen has no influence on the implementation of this method.

The accuracy of the proposed method is evaluated by comparing the individual components of the eddy current density as well as the Lorentz force on the permanent magnet with the results from finite element computations.

### 16 Feb 2017, Instabilities in liquid metal batteries

# Guest Lecture 16 Feb 2017

Oleg Zikanov

University of Michigan Dearborn, USA

**Instabilities in liquid metal batteries**

**Abstract:**

Liquid metal battery is a promising concept of a large-scale stationary energy storage device. It is also an interesting hydrodynamic system rich in complex and yet poorly understood behavior. In particular, there are several ways in which a battery cell can become unstable. We present recent results of the computational and theoretical analysis of three possible mechanisms leading to instability, all related in their origins to low electrical conductivity of the electrolyte. One is the thermal convection caused by the Joule dissipation. Another is a generalization of the ‘metal pad’ instability known for the aluminum reduction cells. Finally, there is a new ‘overturning’ instability related to the interactions of current perturbations with the azimuthal magnetic field induced by the base current.

### 09 Feb 2017, Pinning and trapped field in MgB2- and MT-YBaCuO bulk superconductors manufactured under pressure

# Guest Lecture 09 Feb 2017

Prof. Tetiana Prikhna

National Academy of Sciences of Ukraine

**Pinning and trapped field in MgB2- and MT-YBaCuO bulk superconductors manufactured under pressure**

**Abstract:**

Developed bulk MgB2-and YBaCuO-based materials are competitive candidates for similar applications in cryogenics: for manufacturing fault current limiters, magnetic bearings, MAGLEV transport, electromotors, pumps, generators, special magnets, etc.

The oxygenation of melt–textured (MT) YBaCuO under the high oxygen pressure (16 MPa) allows one to considerably increase the oxygenation temperature, which leads to an increase of the twin density in the Y123 matrix and to a decrease of dislocations, stacking faults and the density of microcracks, and as a result to an increase of the critical current density, jc, and the trapped magnetic field. In MT-YBaCuO, practically free form dislocations and stacking faults and with a twin density of 22-35 μm-1, jc of 100 kA/cm2 (at 77 K, 0 T) has been achieved and the importance of twins in Y123 for the pinning was experimentally demonstrated. The smaller were Y2BaCuO5 (Y211) grains in Y123 matrix and smaller distances between them the higher twin density in Y123 matrix has been observed. Batched-produced MT-YBaCuO samples (38×38×17 mm) demonstrated trapped field of 1.45 T at 77 K.

### 17 Jan 2017, How we Save Lives?

Helena Ramos,

Instituto Superior Técnico Lisboa, Portugal

**How we Save Lives? **

**Abstract:**

Non Destructive Evaluation (NDE) techniques are widely used in several industries in order to control product quality or to ensure the integrity of a part.

A wide variety of methods exist. They involve the application of a suitable form of energy to the specimen under test. One of these forms of energy can be electromagnetic and the most used imply the measurement of a magnetic field.

This presentation starts with a survey of today’s magnetic field sensing elements.

There are many types of magnetic sensors based on different technologies. Traditional inductive eddy current probes based on excitation/detection coils as well as magnetic field transducers shall be analyzed. Different eddy current coil probe configuration and design shall be described. For instance, probes with the same coil or coils to generate the eddy currents and to determine the resulting magnetic field (reflection probe) or probes with separate function coils with detection coils that can be absolute or differential. In the magnetic detection elements Hall sensors, fluxgates, superconducting interference devices (SQUIDS), anisotropic or giant magnetoresistors (AMR and GMR) shall be reported. A comparison of the performances of the different sensors is carried out. Some are very sensitive, able to measure magnetic fields or magnetic field gradients in the region of interest. Some are tiny allowing a good special resolution. Others present a large bandwidth from DC to the MHz zone. All these sensors can be used in different NDE methods.

The second part of the presentation analyzes the details of an inspection, either to detect a defect, to quantify its geometrical characteristics or to measure thickness or determine corrosion. The presentation overlooks the aspects multidisciplinary and interdisciplinary that motivate such area of knowledge as one of the most interesting to develop research in an engineering school.

The approach of this presentation follows some of the recent developments in the magnetic sensors technology and studies the present and future impact of the improvements in the nondestructive evaluation methods.

### 17 Jan 2017, Inspection of Metallic Cracks by Imaging of the Eddy Current Density

Artur Lopes Ribeiro,

Instituto Superior Técnico Lisboa, Portugal

**Inspection of Metallic Cracks by Imaging of the Eddy Current Density **

**Abstract:**

This presentation shows the characterization of cracks in a metallic material using an eddy current testing technique. In this technique we use a special probe that generates a uniform excitation field that diffuses into the metallic material as a plane wave. It has already shown good results in the field of defect detection because, the current is forced to flow in a uniform direction, making it more predictable and easy to interpret the behavior of the induced currents when a crack is present in the metal. However, this technique is limited in the ability to detect cracks when induced currents flow parallel to it. In this paper, a special planar probe was built to remove this difficulty. The probe includes two coils that induce current in the conductor in different directions and two giant magneto-resistive (GMR) sensors positioned perpendicularly to each other to measure the two perpendicular components of the magnetic field. The Inverse problem technique is used to get the current density maps from the magnetic field maps. 2D eddy current density images are obtained to visualize the crack geometry.

# 2016

### 15 Dec 2016, A short Introduction to Thermonuclear Controlled Fusion

Prof. Alessandro Formisano

Seconda Universitá di Napoli

**A short Introduction to Thermonuclear Controlled Fusion**

**Abstract:**

Energy generated from Oil is becoming more and more expensive and pollutant, so many alternatives are being considered.

One of the most promising is the “Controlled Nuclear Fusion”, that is the confinement of a very energetic gas to favour collisions of hydrogen nuclei, which fusing into a single helium atom generate excess energy, which can be used. This is the way the sun and stars work.

Controlled Fusion can be achieved using magnetic confinement. In the seminar, the basics of the nuclear fusion process are introduced, and the technology for magnetic confinement briefly described.

### 13 Dec 2016, MHD Rayleigh-Benard convection confined by a moderate aspect ratio box

Yuji Tasaka, Associate Professor,

Hokkaido University

**MHD Rayleigh-Benard convection confined by a moderate aspect ratio box**

**Abstract:**

We explored transition of Rayleigh-Benard convection affected by a horizontal magnetic field in a horizontal fluid layer of a low Pr fluid confined by a moderate aspect ratio box. In the lecture, typical phenomena caused by low Pr fluids and moderate aspect ratio will be summarized, especially, irregular and regular flow reversals and onset of two-dimensional oscillations. Also, I will introduce some examples of studies using ultrasonic Doppler velocimetry with focusing on characteristics of the line measurement.

Reference:

Yuji TASAKA, Takatoshi YANAGISAWA, Kazuto IGAKI, Tobias VOGT, Till ZUERNER, and Sven ECKERT: “Regular flow reversals in Rayleigh-Bénard convection in a horizontal magnetic field”, Physical Review E, Vol.93, 043109 (2016): 10.1103/PhysRevE.93.043109

Makoto IIMA & Yuji TASAKA: “Dynamics of flow structures and surface shapes in the surface switching of rotating fluid”, Journal of Fluid Mechanics, Vol. 789, pp.402-424 (2016)

Yuji TASAKA, Takufumi KIMURA, Yuichi MURAI: “Estimating the effective viscosity of bubble suspensions in oscillatory shear flows by means of ultrasonic spinning rheometry”, Experiments in Fluids, Vol.56, 1867 (2015): DOI 10.1007/s00348-014-1867-5

### 29 Nov 2016, Experimental and numerical study of electrolyte flow in a cylindrical cavity

James Peréz Barrera

Universidad Nacional Autónoma de México

**Experimental and numerical study of electrolyte flow in a cylindrical cavity**

**Abstract:**

Electrolyte flows have been studied (both experimentally and numerically) in different geometries including rectilinear channels and cylindrical cavities. In this talk, experimental observations and numerical simulations regarding the flow instabilities appearing in a electromagnetic stirrer will be presented. The device consists in a cylindrical cavity formed by two concentric, copper electrodes through which an electric current is applied. Underneath the cavity there is a permanent magnet whose main component of magnetic field is perpendicular to the circular section of the cavity. The interaction of both electric current and magnetic field produces an azimuthal Lorentz force which sets the fluid into motion. For certain experimental conditions, several vortical structures appear and very interesting flow patterns can be observed.

### 20 Sept 2016, Statistical properties of passive scalar in homogeneous turbulence

Prof. Toshiyuki Gotoh

Nagoya Institute of Technology, Japan

**Statistical properties of passive scalar in homogeneous turbulence**

**Abstract:**

One of the properties of turbulent flow is huge tranport power of heat, mass and momentum. Its understanding is indispensable in the natural science, environmental problems and engineering applications. Passive scalar convected by turbulence has extensively been studied since the pioneering work by Kolmogorov, Obukhov and Corrsin.

However, the statistical properties of scalar fluctuations are still not well understood. In the lecture the brief history of research on the passive scalar in turbulence is reviewed and the recent progresses are explained especially from the view points of the theory and the direct numerical simulations by using high performance computers.

### 02 Sept 2016, Making Permanent Magnets While Considering Material Criticality

Cajetan Ikenna Nlebedim

Ames Laboratory,

United States Department of Energy

**Making Permanent Magnets While Considering Material Criticality**

**Abstract:**

The current ubiquitous applications of rare-earth elements (REEs)-based permanent magnets, the increasing need for future electronic devices that depend on high performance magnets and the lopsided geographical distribution of REEs, have resulted in materials criticality. One approach for addressing such criticality is to tailor magnet performance to needs of specific applications. However, the lack of magnets that fit into certain application windows has resulted in designers using magnets much higher in performance than is necessary for the intended applications. Magnets that fit the application space between REE-based permanent magnets and non-REE-based magnets (such as alnico and ceramic magnets) are often called “gap magnets”. Since in most bonded magnets, the magnetic properties of isotropic magnet particles are diluted in non-magnetic polymer binders, they do not fit into the “gap magnet” window.

This talk will focus on using anisotropic powders and taking advantage of magnetic alignment to enhance properties of bonded magnets. The interplay between the physics of magnetism and the viscoelastic properties of polymer-based binders will be discussed.

Acknowledgement

This work was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.

### 28 June 2016, Resolving the fine-scale structure in turbulent Rayleigh-Benard Convection

Dr. Janet Scheel

Occidental College, Los Angeles

**Resolving the fine-scale structure in turbulent Rayleigh-Benard Convection**

**Abstract:**

In Rayleigh-Benard convection, a confined fluid is heated from below and cooled from above. Results from very well-resolved direct numerical simulations of Rayleigh-Benard convection in the turbulent regime will be presented. This includes the detection of a rare head-on collision between two thermal plumes resulting in extremely large values of the kinetic energy dissipation rate. The behavior of the boundary layers will also be discussed. Finally, results will be shown for very low Prandtl numbers representing liquid metals.

### 31 May 2016, Radiative Hydrodynamics and Radiative MHD

Prof. Ben-Wen Li

Institute of Thermal Engineering

School of Energy & Power Engineering

Dalian University of Technology, China

**Radiative Hydrodynamics and Radiative MHD**

**Abstract:**

The mathematical descriptions for radiative hydrodynamics (R-HD) and radiative MHD (R-MHD) are presented, and the corresponding physical phenomena are revealed numerically by collocation spectral methods. The topic mainly focuses on the efficient and accurate numerical skills for the combinations of thermal radiation and hydrodynamics or magnetohydrodynamics. Lots of new developments in my group will be introduced.

### 24 May 2016, Thermal convection in liquid metal blankets of fusion reactor

Prof. Oleg Zikanov

University of Michigan, USA

**Thermal convection in liquid metal blankets of fusion reactor**

**Abstract:**

It has been recently realized that the effect of thermal convection will play an essential role in the operation of liquid metal blankets for future nuclear fusion reactors. In the presence of a strong magnetic field, convection will appear in a counterintuitive, in many aspects yet unknown form. We investigate the effect using numerical simulations of flows and heat transfer in simplified models of several blanket configurations.

### 26 April 2016, Unraveling Jupiter’s Internal Dynamics

Dr. Johannes Wicht

Max Planck Institute for Solar System Research

Göttingen

**Unraveling Jupiter’s Internal Dynamics**

**Abstract:**

This summer NASA’s Juno mission will finally arrive at its target planet Jupiter. The mission is geared towards exploring the planet’s internal structure and dynamics which remains largely unknown. Measurement of the magnetic field produced by dynamo process in Jupiter’s deep interior provides important constraints. We use numerical simulations to explore the dynamo process and its connection to the jet winds that not only shape the planets cloud layer but also leave a magnetic signature. The results provide important predictions and will help to interpret the Juno mission results.

### 12 April 2016, Experimental investigation of rotating liquid metal flows

Tobias Vogt

Helmholtz-Zentrum

Dresden-Rossendorf

**Experimental investigation of rotating liquid metal flows**

**Abstract:**

Several experiments considering electromagnetically driven liquid metal flows in cylindrical vessels will be presented. The focus of the experiments is ranging from meteorological and geophysical effects like inertial waves and tornado-like vortices. Besides, flows with industrial relevance like the mixing of floating particles into a metallic melt or the mixing enhancement in gas stirred ladles is considered. Different ultrasound-based measurement techniques were used in these experiments whereby the ultrasound-Doppler-velocimetry (UDV) is the most important one.

### 08 March 2016, Scaling of large-scale quantities in Rayleigh-B´enard Convection

Ambrish Pandey

Indian Institute of Technology Kanpur-208016, India

**Scaling of large-scale quantities in Rayleigh-B´enard Convection**

**Abstract:**

Using direct numerical simulations of Rayleigh-B´enard convection in rectangular boxes, we

study the scaling of large-scale quantities such as the Nusselt (Nu) and Péclet (Pe) numbers for moderate Rayleigh (Ra) numbers. We observed that Nu ∼ Ra^{γ} and Pe ~ Ra^{ζ} , where γ varies from 0.27 to 0.32 and ζ from 0.43 to 0.61 when the Prandtl number is changed between 0.02 and ∞. For very large Prandtl numbers, we observed that the kinetic energy spectrum scales with wavenumber* k as k ^{−13/3}* in the inertial range. Moreover, the scalings of large-scale quantities and energy spectrum are similar in 2D and 3D for very large Prandtl numbers. We also found that the corner rolls and the vortex reconnections are absent during a ﬂow reversal in 2D boxes with stress-free boundary condition, whereas they play important roles during a reversal in the boxes with rigid walls.

# 2015

### 06 Oct 2015, Recent Progress of Various Electromagnetic Metallurgical Techniques at the Key Laboratory of EPM

Prof. EnGang Wang

Northeastern University Shenyang, China

**Recent Progress of Various Electromagnetic Metallurgical Techniques at the Key Laboratory of EPM**

**Abstract:**

The Key Laboratory of EPM at Northeastern University of Shenyang (China) is working on various topics. The focus today is on some of these electromagnetic metallurgical techniques, including:

- the control of fluid flow in continuous casting mould with vertical EMBr

- how to improve the external and internal quality of superalloys

- billets in continuous casting processes with electromagnetic fields

### 17 Sept 2015, Data-driven spectral decomposition and forecasting of ergodic dynamical systems

Prof. Dimitris Giannakis

Courant Institute of Mathematical Sciences, New York, USA

**Data-driven spectral decomposition and forecasting of ergodic dynamical systems**

**Abstract:**

We discuss a framework for dimension reduction, mode decomposition, and nonparametric forecasting of data generated by ergodic dynamical systems. This framework is based on a representation of the Koopman group of unitary operators governing dynamical evolution in a smooth orthonormal basis acquired from time-ordered data through the diffusion maps algorithm. Using this representation, we compute Koopman eigenfunctions through a regularized advection-diffusion operator, and employ these eigenfunctions in dimension reduction maps with projectible dynamics and high smoothness for the given observation modality. In systems with pure point spectra, we construct a decomposition of the generator of the Koopman group into mutually commuting vector fields, which we reconstruct in data space through a representation of the pushforward map in the Koopman eigenfunction basis. We also use a special property of this basis, namely that the basis elements evolve as simple harmonic oscillators, to build nonparametric forecast models for arbitrary probability densities and observables. We present applications to dynamical systems on tori and satellite observations of atmospheric convection.

### 16 June 2015, Mass measurement activities at National Institute of Metrology, Beijing (P.R. China)

Prof. Wang Jiang

National Institute of Metrology, Beijing, China

**Mass measurement activities at National Institute of Metrology, Beijing (P.R. China)**

**Abstract:**

Introduction to: Air density measurement system developed for air bouyance correction, weight volume measurement system based on the acoustic method, and uncertainty evaluation for a system of weighing equations to determine microgram weights.

### 09 June 2015, Thermal convection in liquid metal flows

Dr. Janet Scheel

Occidental College, Los Angeles, USA

**Thermal convection in liquid metal flows**

**Abstract:**

Very high resolution direct numerical simulations of Rayleigh-Benard Convection for low Prandtl number fluids (Pr=0.021, Pr=0.005) and Rayleigh numbers between 10^{6}-10^{8} will be presented. The scaling laws for global heat and momentum transfer will be discussed. Then the statistics at constant Grashof number will be explored, including principal strain rates and contributions to the enstrophy production and dissipation. Finally a detailed boundary layer analysis will be presented. Low Prandtl number convection has direct application to convection in liquid metals, and can also shed light on the convection in the earth’s liquid metal core and in stars which have even lower Prandtl numbers.

### 02 June 2015, Contactless Flow Rate Sensor for Heavy Liquid Metals

Dr. Ing. S. Lenk

SAAS Gmbh,

Bannewitz, Germany

**Contactless Flow Rate Sensor for Heavy Liquid Metals**

**Abstract:**

Control of the flow rate of liquid metals is required in a number of technological processes such as the cooling of liquid metal cooled nuclear reactors, transmutation systems and the dosing and casting of liquid metals. Electromagnetic flow meters play an important role in the diagnostics and automatic control of such processes in order to measure the integral flow rate in arbitrary pipes and channels with electrically conducting and non-conducting walls. A number of different electromagnetic flow meter designs have been developed starting from the end of the forties of the last century.

Commercial electromagnetic flow meters are typically based on the flow-induced electrical voltage measurements by electrodes in direct contact to the melt in a steady magnetic field. In view of the typical problems coming along with applications at liquid metal flows such as high temperatures, interfacial effects and corrosion, the main disadvantage of this type of flow meter is the electrical contact to the liquid metal, which is necessary to measure the electric potential difference. Therefore, contactless operating measurement techniques are very attractive for liquid metal applications.

The SAAS Corporation and the Institute of Fluid Dynamics (Helmholtz-Zentrum Dresden-Rossendorf e. V.) developed together a flow meter which uses the measuring principle of transmitting an alternating current voltage over a transformer with a large head gap. The measuring signal is generated by the phase shifting of two sinusoidal voltages. The geometry of the applied magnetic field in proportion to the selected pipe cross section has a significant impact on the sensitivity of the measuring device.

Furthermore extensive studies have been conducted to find and analyze measurement uncertainty due to temperature influences and how to reduce them. At this stage of the development the commercialized measuring device EMD ps manufactured by SAAS GmbH is available in several interior diameters and has been proven effective in multiple applications.

### 26 May 2015, Liquid metal heat transfer affected by magnetic field

Dr. Belyaev Ivan

Head of laboratory 2.1.2.1 JIHT RAS

Moskow, Russia

**Liquid metal heat transfer affected by magnetic field**

### 19 May 2015, Hybrid ground-source heat pump systems

Prof. Dr. Alexander Georgiev

Lehrstuhl für Mechanik

Technische Universität von Sofia, Filiale in Plovdiv, Bulgarien

**Hybrid ground-source heat pump systems**

**Abstract:**

Ground source heat pump (GSHP) is a heating and/ or cooling system that transfers heat to or from the ground. The GSHP systems can achieve better energy performance where building heating and cooling loads are well balanced all the year round. However, most buildings in warm-climate or cold-climate areas have unbalanced loads, dominated by either cooling loads or heating loads. An alternative to decrease the initial cost of the GSHP system and, at the same time, to improve the system performance is to employ a supplemental heat rejecter or heat absorber, which is called the hybrid GSHP (HGSHP) system.

### 24 Feb 2015, Measurements of near wall phenomena in wall-bounded turbulence with modern imaging techniques

Prof. Dr.-Ing. habil. Christoph Brücker

Technische Universität Bergakademie Freiberg

**Measurements of near wall phenomena in wall-bounded turbulence with modern imaging techniques**

**Abstract:**

The details of turbulent momentum and heat exchange near walls is still a great challenge in measurements of turbulent boundary layer flows. Especially the correlation between large scale structures in the boundary and local changes in the wall transfer rates such as the heat –transfer and the wall shear stress as source of viscous momentum-transfer. The topology of the near-wall flow is therefore of high interest, including the evolution of critical points and their dynamics. An example is the flow along the crown over a moving piston or in a classical turbulent boundary layer in wall-parallel planes within the viscous sublayer. Such measurements are difficult in classical PIV and solutions are shown to overcome these limitations.

### 19 Feb 2015, Temperature measurement with LIDAR

Dr. Andreas Behrendt

Universität Hohenheim

**Temperature measurement with LIDAR**

### 17 Feb 2015, Numerical simulations of gravity-driven instabilities in porous media

Prof. Bernard Knaepen

Physics Department,

Université Libre de Bruxelles

**Numerical simulations of gravity-driven instabilities in porous media**

**Abstract:**

Flows in porous media are encountered in several environmental applications such as CO2 sequestration and transport of green house gases in sea ice. In this presentation we describe the onset of convection in such media by analysing gravity induced flow instabilities. In particular, we focus our attention on instabilities arising because of initial density gradients or those resulting from double diffusion (or a combination of both). The results presented are obtained using a finite volume numerical code but also through experimental investigation using a Hele-Shaw cell. In both cases, a classification of regimes with respect to the control parameters will be described along with quantitative diagnostics such as mixing length growth rates, kinetic energy evolution, etc.

### 12 Feb 2015, Thermographic Phosphor particles for temperature measurement

Prof. Frank Beyrau

Universität Magdeburg

**Thermographic Phosphor particles for temperature measurement**

### 27 Jan 2015, Closed-loop turbulence control using machine learning

Prof. Bernd Noack

Institute PPRIME, Poitiers, France

Technische Universität Braunschweig, Germany

**Closed-loop turbulence control using machine learning**

**Abstract:**

Active turbulence control is a rapidly evolving, interdisciplinary ﬁeld of research. In particular, closed-loop control with sensor information can oﬀer distinct beneﬁts over blind open-loop forcing. The range of current and future engineering applications of closed-loop turbulence control has truly epic proportions, including cars, trains, airplanes, jet noise, air conditioning, medical applications, wind turbines, combustors, and energy systems. Many problems of the Research Training School ’LORENTZ FORCE’ belong to that portfolio.

A key feature, opportunity and technical challenge of closed-loop turbulence control is the inherent nonlinearity of the actuation response. For instance, excitation at a given frequency will aﬀect also other frequencies. Such frequency cross-talk is not accessible in any linear control framework. We propose a novel generic nonlinear feedback control design strategy with a model-free exploration of control laws preceding a model-based exploitation. During the exploration, machine learning techniques discover the best a priori unknown actuation mechanisms in an unsupervised manner. During the exploitation, a class of winning actuation mechanisms can be framed in reduced-order models. The approach is demonstrated for drag reduction of a D-shaped body, for the TUCOROM mixing layer control experiment, and for separation mitigation of shear ﬂow experiments at PMMH, LML and PRISME.

### 20 Jan 2015, Liquid Metal Heat Transfer Specific in a Tokamak Reactor

**cancelled!**

Dr. Ivan Belyaev

Joint Institute for High Temperatures of the Russian Academy of Sciences (Moscow)

**Liquid Metal Heat Transfer Specific in a Tokamak Reactor**

**Abstract**

Complex experimental study and numerical simulation of liquid metal flow and heat transfer in various configurations affected by longitudinal or transverse magnetic field under conditions close to tokamak reactor have been held. Heat transfer specific in these conditions is the combined exposure of a strong magnetic field and thermo-gravitational forces, which manifests itself in previously unknown effects. Among these effects: the existence in some modes of MHD heat transfer areas of “degraded” heat transfer, the extremely uneven distribution of heat transfer coefficients on the perimeter of the tube, abnormally high temperature fluctuations near wall.

### 16 Jan 2015, Optimization of Electromagnetic Devices Using Evolutionary Algorithms

Prof. Christian Magele

TU Graz

**Optimization of Electromagnetic Devices Using Evolutionary Algorithms**

# 2014

### 09 Dec 2014, Flexible Discretization in Computational Electromagnetics and Computational Fluid Dynamics

Prof. Manfred Kaltenbacher

Institute of Mechanics and Mechatronics, Vienna University of Technology

**Flexible Discretization in Computational Electromagnetics and Computational Fluid Dynamics**

**Abstract:**

We investigate flexible discretization techniques for the approximate solution of partial differential equations (PDEs). In order to keep as much flexibility as possible, we use independently generated grids which are well suited for approximating the solution of decoupled local sub-problems in each subdomain. Therefore, we have to deal with the situation of non-conforming grids appearing at the common interface of two subdomains. Special care has to be taken in order to define and implement the appropriate discrete coupling operators. We apply the Finite Element (FE) method and use two approaches to handle non-conforming grids: (1) Classical mortaring and (2) Nitsche type-mortaring. In the first approach we guarantee the strong coupling of the flux by introducing a Lagrange multiplier and coupling of the primary physical quantity in a weak sense. The Nitsche type-mortaring does not need the additional Lagrange multiplier and handles the coupling by symmetrizing the bilinear form and adding a special interface term to penalize the jump of the primary physical quantity.

To demonstrate the applicability of the developed numerical schemes, we will present two applications: (1) Gear wheel sensor (dynamic, rotating interface) (2) Flow meter device (coupling of fluid dynamics with structural mechanics).

### 25 Nov 2014, MAGNETIC LEVITATION FORCE MEASUREMENT SYSTEM AT ANY LOW TEMPERATURES FROM 20K TO 300K

Sükrü Celik

Sinop University, Faculty of Engineering and Architecture, Department of Energy Systems Engineering, Sinop, Turkey

**MAGNETIC LEVITATION FORCE MEASUREMENT SYSTEM AT ANY LOW TEMPERATURES FROM 20K TO 300K**

**Abstract:**

Most of the magnetic levitation force measurements in previous studies were performed at liquid nitrogen temperatures. For the levitation force of MgB2 and iron based superconducting samples, magnetic levitation force measurement system is needed. In this study, magnetic levitation force measurement system was designed. In this system, beside vertical force versus vertical motion, lateral and vertical force versus lateral motion measurements, the vertical force versus temperature at the fixed distance between permanent magnet PM – superconducting sample SS and the vertical force versus time measurements were performed at any temperatures from 20 K to 300 K. Thanks to these measurements, the temperature dependence, time dependence, and the distance (magnetic field) and temperature dependences of SS can be investigated. On the other hand, the magnetic stiffness MS measurements can be performed in this system. Using the measurement of MS at different temperature in the range, MS dependence on temperature can be investigated. These measurements at any temperatures in the range help to the superconductivity properties to be characterized.

This work was supported by TÜBİTAK – the Scientific and technological research council of Turkey under project of MFAG – 110T622. This system was applied to the Turkish patent institute with the application number of 2013/13638 on 22/11/2013.

### 04 Nov 2014, IPUL experience in design of EM induction Permanent Magnets Pumps

Dr. Phys. I.Bucenieks

Institute of Physics, Latvian University

**IPUL experience in design of EM induction Permanent Magnets Pumps**

### 28 Oct 2014, Surrogate Models in Nondestructive Evaluation

Dr. Sandor Bilicz,

Budapest University of Technology and Economics,

Dept. of Broadband Infocommunications and Electromagnetic Theory**Surrogate Models in Nondestructive Evaluation**

**Abstract:**

In engineering science, researchers usually work with computer simulations which provide them easy-to-control alternatives of the costly construction of prototypes. Nowadays, very accurate numerical simulators are available for problems that are modeled by partial differential equations, e.g., based on the finite element method.

However, the simulation accuracy usually imposes a computational burden that might result in extreme computational times even on strong computers.

Moreover, in certain applications, not only one but a sequence of computer simulations has to be performed which can make the whole procedure hopeless. Typically, such scenarios occur in the design optimization and in the iterative solution of inverse problems. One usually has to face with both issues in nondestructive evaluation.

In this talk, a possible way for the reduction of the computational burden is discussed, the so-called surrogate modeling that aims at replacing the heavy simulations by cheap-to-evaluate models. The presented surrogate models consist basically in a database (training set) including pairs of input parameters and corresponding output data, and an interpolation method fitted to the stored samples. When generating the database, many aspects are taken into account, e.g., the required precision, the sensitivity of the output data to changes in the inputs and the interpolation subsequently fitted to the samples. The presented adaptive sampling schemes can take into account many of these factors. Concerning the interpolation, piecewise linear and global kriging methods are in use, with respect to the application. Special emphasis is put on the "curse of dimensionality", i.e., on the exponential growth of the computational burden with increasing number of model parameters.

The discussed methods treat the computer simulation as a "black-box", so the underlying physics is hidden at the level of surrogate modelling, making possible the applicability to a wide range of problems. The illustrative examples are drawn from the eddy-current nondestructive testing where the inverse problem of defect reconstruction is a central problem because usually limited computational times are required in the industrial applications.

### 24 Oct 2014, Why, how and when MHD turbulence at low Rm becomes three-dimensional

Prof. Alban Potherat

Coventry University UK

**Why, how and when MHD turbulence at low Rm becomes three-dimensional**

**Abstract:**

Magnetohydrodynamic (MHD) turbulence at low Magnetic Reynolds number is experimentally investigated by studying a liquid metal flow in a cubic domain. We focus on the mechanisms that determine whether the flow is quasi-two dimensional, three-dimensional or in any intermediate state. To this end, forcing is applied by injecting a DC current I through one wall of the cube only, to drive vortices spinning along the magnetic field.

Depending on the intensity of the externally applied magnetic field, these vortices extend part or all the way through the cube. Driving the flow in this way allows us to precisely control the forcing intensity but also its dimensionality. A comparison with the theoretical analysis of this configuration singles out the influences of the walls and of the forcing on the flow dimensionality. Flow dimensionality is characterised in several ways: first, we show that when inertia drives three-dimensionality, the velocity near the wall where current is injected scales as Ub ∼ I2/3. Secondly, we show that when the distance lz over which momentum diffuses under the action of the Lorentz force (Sommeria & Moreau (1982)) reaches the channel width h, the velocity near the opposite wall Ut follows a similar law with a correction factor (1−h/lz) that measures three-dimensionality.

When lz < h, by contrast, the opposite wall has less influence on the flow and Ut ∼ I1/2. The central role played by the ratio lz/h is confirmed by experimentally verifying the scaling lz ∼ N1/2 put forward by Sommeria & Moreau (1982) (N is the interaction parameter) and finally, the nature of the three-dimensionality involved is further clarified by distinguishing weak and strong three-dimensionalities previously introduced by Klein & Poth´erat (2010). It is found that both types vanish only asymptotically in the limit N → ∞. This provides evidence that because of the no-slip walls, 1) the transition between quasi-two dimensional and three dimensional turbulence does not result from a global instability of the flow, unlike in domains with non-dissipative boundaries (Boeck et al. (2008)), and 2) it doesn’t occur simultaneously at all scales.

### 01 Oct 2014, Uncertainty quantification in computational electromagnetics and stochastic finite integration technique

Prof. Luca di Rienzo

Politecnico di Milano, Italy

**Uncertainty quantification in computational electromagnetics and stochastic finite integration technique**

**Abstract:**

Electromagnetic computations rely on the perfect knowledge of material parameters. However, for a wide range of examples in electrical engineering, some uncertainty should be associated with that knowledge in the modeling process. In order to quantify the uncertainty of the output quantities of interest coming from the lack of knowledge of the input material parameters, the Monte Carlo method could be applied. However the convergence is very slow and, if the single deterministic computation is not fast enough, the total computational time becomes prohibitive. The spectral stochastic approach is able to dramatically reduce the computational time. After a brief resume of the different techniques for uncertainty quantification, a stochastic Finite Integration Technique for low-frequency electromagnetism will be presented.

Luca Di Rienzo received the M. S. degree (cum laude) and the Ph. D. degree in electrical engineering from Politecnico di Milano, in 1996 and 2001 respectively. From November 2000 to December 2004 he was research assistant with the Department of Electrical Engineering of Politecnico di Milano. Since 2005 he has been an assistant professor with the same department (now named Department of Electronics, Information, and Bioengineering) and he teaches basic circuit theory. At present, his research interests are in the field of computational electromagnetics (CEM) and include magnetic inverse problems, surface impedance boundary conditions, and uncertainty quantification in CEM. He is a senior member of IEEE (EMC and Magnetics Societies) and a member of the International Compumag Society (ICS). In February 2014 he received the award of the national scientific qualification as associate professor in electrical engineering.

### 18 Aug 2014, Mixing in a liquid metal electrode

Prof. Douglas H. Kelley

Assistant Professor of Mechanical Engineering

University of Rochester

**Mixing in a liquid metal electrode**

**Abstract:**

Adding large-scale energy storage to Earth's electrical grids would accommodate demand variations, reduce the need for gas-fired peakers, and enable broad deployment of wind and solar generation. Liquid metal batteries are currently being commercialized as a promising and economically viable technology for grid-scale storage. But because these batteries are entirely liquid, fluid flow and instabilities affect battery robustness and performance. I will talk about those affects and show experimental measurements of a liquid metal electrode. The measurements demonstrate a critical electrical current density above which the convective flow organizes and gains speed, improving battery efficiency. I will finish with a discussion of my group's ongoing work to build predictive battery models.

### 07 July 2014, Studying properties of single crystals and bulk samples using synchrotron radiation

Dr. Anastasiya Kolchynska

Department of Condensed Matter Physics

Faculty of Mathematics and Physics Charles University, Prague

**Studying properties of single crystals and bulk samples using synchrotron radiation**

**Abstract:**

Synchrotrons are powerful tools which allow to study properties and effects in different kind of samples including single crystals and polycrystals, that are difficult or impossible to execute on ordinary X-ray diffractometers. In this talk I will give two examples of such study. The first one will focus on the study of forbidden reflections in single crystals and subsequent numerical simulations required for further processing of obtained data. The second one will give an idea about XMCD method and its application on double perovskite bulk samples.

### 01 July 2014, Approximate modeling of the leftward flow and morphogen transport in the embryonic node

A.V. Kuznetsov

Dept. of Mechanical & Aerospace Engineering

North Carolina State University

**Approximate modeling of the leftward flow and morphogen transport in the embryonic node**

**Abstract:**

We developed an approximate method for modelling the flow of embryonic fluid in a ventral node. We simplified the problem as flow in a 2D cavity; the effect of rotating cilia was modeled by specifying a constant vorticity at the edge of the ciliated layer. We also developed an approximate solution for morphogen transport in the nodal pit. The solutions were obtained utilizing the proper generalized decomposition (PGD) method. We compared our approximate solutions with the results of numerical simulation of flow caused by the rotation of 81 cilia, and obtained reasonable agreement in most of the flow domain. We discuss locations where agreement is less accurate. The obtained semi-analytical solutions simplify the analysis of flow and morphogen distribution in a nodal pit.

### 01 July 2014, An Introduction to Quantum Turbulence

Martin Jackson

Superfluidity Laboratory, Low Temperature Physics Department, Charles University in Prague

**An Introduction to Quantum Turbulence**

**Abstract:**

When cooled below 2.17 K, 4He enters the so-called superfluid phase - an extraordinary manifestation of quantum mechanics at macroscopic length scales. Superfluid helium can flow freely, without the dissipative effect of viscous forces and its local rotation is constrained to discretely quantised vortex lines. These vortex lines can tangle to form quantum turbulence. It is hoped that studying quantum turbulence could provide a stepping-stone to fully understanding classical turbulence; ''the last great unsolved problem of classical physics.'' In this presentation, I will provide a basic introduction to superfluidity and quantum turbulence and discuss some of the techniques used in this field of research.

### 24 June 2014, Pattern formation in complex systems

Prof. Janet Scheel

Occidental College, USA

**Pattern formation in complex systems**

### 23 June 2014, Micro/Nano Scale Energy Conversion using Knudsen Process

Dr. Gülru Babaç

Istanbul Tehcnical University, Institute of Energy

**Micro/Nano Scale Energy Conversion using Knudsen Process**

**Abstract:**

In micro/nano scale systems, the mean free path of the gas molecules is comparable to the characteristic size of the domain, and this changes the flow behavior in the system quite considerably. Several physical effects become important which are generally ignored in macroscale and also some new effects can be introduced which can open up new energy conversion technologies. In this presentation, these new effects will be discussed in transport phenomena and thermodynamic points of view.

### 28 May 2014, Time Scale Exploitation to frame Simplified Models in Plasmas

Dr. Sita Sundar

University of California, San Diego

**Time Scale Exploitation to frame Simplified Models in Plasmas**

**Abstract:**

Certain fundamental aspects of the plasma behavior have a dominant dynamical role at time scales at which the lighter electron species respond. Simplified fluid models (existing as well as extended) based on the idea of time scale separation have been adopted to study certain problems of fundamental interest. The electron shear flow driven instabilities and coherent nonlinear solutions that may form in this domain of plasma response have been explored. The magnetized and relativistic nature of the electron fluid produces interesting features in the electron shear flow driven Kelvin - Helmholtz (KH) like mode of the plasma. The study of the existence and dynamics of nonlinear coherent structure in the coupled laser plasma system will be presented. Questions pertaining to the stability of some of these structures will also be discussed.

### 13 May 2014, Simulations of bubbles in liquid metals with and without application of external fields

Prof. Jochen Fröhlich

Institute of Fluid Mechanics, Technische Universität Dresden, Germany

**Simulations of bubbles in liquid metals with and without application of external fields**

**Abstract:**

Gas bubbles in liquid metals find numerous applications in metallurgical engineering, casting, and energy process engineering. For such gas-liquid metal two-phase flows, external magnetic fields provide an attractive possibility to control the bubble motion in a contactless way. As experiments in liquid metal face substantial difficulties, simulations constitute an attractive alternative to study such two-phase flows. Numerical approaches, however, also require sizable effort due to the demanding parameter range, characterized by high density ratios, high Reynolds numbers and defomability of the bubble shape. At the Institute of Fluid Mechanics of TU Dresden, a numerical method has been developed over the last years which is particularly suited for this situation. It is based on a bubble-resolving apporach representing the bubble shape by a front-tracking method and coupling it via an immersed boundary method to the fluid [1]. Various levels of modelling the bubble shape and the coupling condition on the phase boundary are available, allowing to account for variable bubble shape [2] and even for coalescence [3]. After describing essential features of the numerical method the talk will discuss applications to several configurations, ranging from a single bubble in a vertical magnetic field [5] to a bubble swarm with application of an electric and a magnetic field [4].

Simulation of a bubble chain injected into liquid metal.Iso-contour of absolute value of instantaneous velocity.

Bubbles in liquid metal under the influence of a horizontal magnetic field and an orthogonal horizontal electric field.

- T. Kempe, J. Fröhlich. An improved immersed boundary method with direct forcing for the simulation of particle laden flows, J. Comput. Phys., 231:3663-3684, 2012.
- S. Schwarz, J. Fröhlich, Representation of deformable bubbles by analytically defined shapes in an immersed boundary method, Int. Conf. Num. Anal. Appl. Math., Kos, Greece, 1479:104, 2012
- S. Schwarz, S. Tschisgale, J. Fröhlich, Modeling of bubble coalescence in phase-resolving simulations by an immersed boundary method, Paper ICMF-750 at ICMF 2013, Jeju, Korea, May 26 - 31, 2013.
- S. Heitkam, S. Schwarz, C. Santarelli, J. Fröhlich, Influence of an electromagnetic field on the formation of wet metal foam, Eur. Phys. J. Special Topics, 220:207–214, 2013.
- S. Schwarz, J. Fröhlich, Numerical study of single bubble motion in liquid metal exposed to a longitudinal magnetic field, Int. J. Multiphase Flow, published online 13 March 2014.

### 06 May 2014, Magnetohydrodynamic turbulence: cascades & convection

Prof. Wolf-Christian Müller

Plasma-Astrophysik, TU Berlin

**Magnetohydrodynamic turbulence: cascades & convection**

**Abstract**

The nonlinear dynamics of plasma turbulence is tremendously important for the evolution of many astrophysical systems - but unfortunately not very well understood. The talk will focus on some new insights gained with regard to the energetics and transport properties of plasma turbulence described in the magnetohydrodynamic approximation. It will also venture out to the realm of convectively-driven turbulence.

### 29 April 2014, Measuring techniques for experimental investigations and monitoring of liquid metal flows

Dr. Sven Eckert

Helmholtz-Zentrum Dresden-Rossendorf, Magnetohydrodynamik

**Measuring techniques for experimental investigations and monitoring of liquid metal flows**

**Abstract:**

The safe and reliable operation of liquid metal systems requires corresponding measuring systems and control units, both for the liquid metal single-phase flow as well as for bubble-laden liquid metal two-phase flows. Moreover, significant research effort is permanently focused on the optimization of technologies and facilities for materials processing such as smelting, refining and casting of metals and alloys. The main objectives are an improvement of the final product quality, an enhancement of the process efficiency and an economical consumption of resources and energy. Further developments of processes involving metallic melts require a better, detailed knowledge about the flow structure and the transport properties of the flow. Numerical simulations could provide a better understanding of the complex flow behavior, but, experimental data are indispensable with respect to a validation of the respective CFD codes. The determination of flow quantities in liquid metals is considerably impeded by the special material properties. Powerful optical methods as used for measurements in transparent liquids are obviously not applicable in molten metals. Further serious restrictions arise from the high temperature or the chemical reactivity of the melt. As a consequence there is a very constrained choice of commercially available techniques to measure the velocity structure of fluid flows at elevated temperatures.

The presentation reports on established methods and new developments in the field of measuring techniques for liquid metal flows. This review is focused on measurements of the flow rate and the local velocity field as well as on the characterization of liquid metal two-phase flows and solidifying melts. During the last two decades considerable effort was spent by miscellaneous researcher groups to provide new solutions for measurements of flow fields in liquid metals. The presentation intends to summarize different approaches and attempts to account on perspectives, particularly in view of some recent developments.

### 04 March 2014, Cryogenics for HTS-Applications

Dr. Andreas Kade, Dr. Gabriele Spörl

Institut für Luft- und Kältetechnik gemeinnützige Gesellschaft mbH Dresden

Hauptbereich Kryotechnik und Tieftemperaturphysik

**Cryogenics for HTS-Applications**

**Abstract:**

The Institut für Luft- und Kältetechnik (Institute of Air Handling and Refrigeration) in particular the main department “Cryogenics and Low Temperature Physics” will be presented and a short introduction in the basics of cryogenics will be given as follows:- What is the meaning of cryogenics?- How can I reach low temperatures?- Cooling devices and cryostat- High temperature superconductors and its applications in measuring techniques, engines, power grid systems and medicine

### 21 Jan 2014, Magnetic instabilities in Taylor-Couette flows

Dr. Marcus Gellert

Leibniz-Institut für Astrophysik Potsdam (AIP)

**Magnetic instabilities in Taylor-Couette flows**

**Abstract:**

Some astrophysical phenomena (such as the slow rotation of neutron stars and white dwarfs or the rigid rotation of the solar core) could be explained by the action of magnetic instabilies of (toroidal) magnetic fields in the radiative zones of stars. The enhanced angular momentum transport outwards due to such an instability leads to a faster spin-down process. How liquid metal experiments help us to understand some basic properties of these instabilities, is the subject of the talk.

# 2013

### 05 Nov 2013, Application of optical flow measurement techniques in research and technology

Dr. Christian Willert

Deutsches Zentrum für Luft- und Raumfahrt (DLR)

**Application of optical flow measurement techniques in research and technology**

### 29 Oct 2013, Transfer operator based numerical analysis of time-dependent transport

Prof. Kathrin Padberg-Gehle,

TU Dresden

**Transfer operator based numerical analysis of time-dependent transport**

**Abstract:**

Numerical methods involving transfer operators have only recently been recognized as powerful tools for analyzing and quantifying transport processes in time-dependent systems. A transfer operator is a linear operator that describes the evolution of densities and thus encodes crucial information about the global behavior of the underlying

(autonomous or nonautonomous) dynamical system.

After an introduction to the basic concepts and the numerical tools we will discuss several different constructions that allow us to extract coherent structures and dynamic transport barriers in time-dependent flows.

### 14 Oct 2013, Measurements of dendritic growth velocities in undercooled metallic melts under static magnetic fields

Jianrong GAO

Northeastern University Shenyang, China

**Measurements of dendritic growth velocities in undercooled metallic melts under static magnetic fields**

**Abstract:**

Dendritic growth in undercooled melts has been intensively studied over the past fifty years. However, the measured growth velocities in a low undercooling region show a large discrepancy with the predictions of the current theories. This discrepancy has been ascribed to an effect of artificial or natural convection in the undercooled melts. In order to investigate the effect of melt flow on dendritic growth systematically, we built up a new experimental set-up by combining a large-bore superconducting magnet, a high-speed camera, a pyrometer with the glass fluxing facility. With this setup, we measured growth velocities of undercooled melts of pure nickel and nickel-silicon alloys under magnetic fields up to 6 T. Our data showed that the dendritic growth velocities in the low undercooling region decrease with increasing intensity of the magnetic field first, but increase with increasing intensity of the magnetic field after going through a minimum at 3 T. Such a complex dependence of the growth velocities on the magnetic field can be explained by considering actions of different Lorentz forces on melt flow around the dendritic tip.

### 08 Oct 2013, Aircraft fuselage sizing with multilevel optimization

Margherita Porcelli

Dipartimento di Matematica

Università di Bologna, Italy

**Aircraft fuselage sizing with multilevel optimization**

**Abstract**

We address the structural optimization problem of sizing an aircraft fuselage. The problem consists in computing the dimensions of the different elements constituting a fuselage minimizing the total mass subject to some mechanical constraints. Mathematically, the problem may be formulated as a very large nonlinear optimization problem subjected to several nonlinear inequality constraints.

We show that this problem possesses a natural hierarchical structure that can be exploited by a multilevel approach. This approach is innovative in the industrial sector and represents a promising alternative to the commonly employed decomposition strategies. Hence, we propose a multilevel procedure which embeds the Recursive Multilevel Trust Region method [1] into an Augmented Lagrangian framework. Some results on both academic and industrial test cases are presented.

[1] Gratton, S. Mouffe, M. Toint, Ph. L. and Weber-Mendonca M., A recursive trust-region method in infinity norm for bound-constrained nonlinear optimization, IMA J. Numer. Anal., 28(4), 827--861, 2008.

### 25 June 2013, DGIST's R&D in Thermoelectric Technology

Prof. Hoyoung Kim

Daegu Gyeongbuk Institute of Science and Technology(DGIST)

Korea

**DGIST's R&D in Thermoelectric Technology**

### 20 June 2013, Why, how and When electrically driven flows and MHD turbulence become three-dimensional

A. Potherat,

Coventry University

**Why, how and When electrically driven flows and MHD turbulence become three-dimensional**

**Abstract:**

Inspired by the seminal theoretical work of Someria and Moreau (JFM 1982), we present an attempt to inventorise the mechanisms that determine the dimensionality of electrically driven flows and magnetohydrodynamic (MHD) turbulence. The approach consists of experimentally probing a variety of flow regimes obtained by driving a square array of vortices in a liquid metal exposed to high magnetic fields.

We show experimentally that in channel flows normal to the field and electrically forced through one of the channel walls, the intensity of turbulent fluctuations scales as Re when the flow is quasi-2D, Re^{2/3} when the flow is 3D but intense near both walls, and Re^{1/2} if it is mostly concentrated along one wall only. We also partly confirm the theoretical prediction of Sommeria and Moreau that structures of transversal wavelength k become quasi-2D when they exceed a critical size k= Nt^{1/2} , where the true interaction parameter Nt represents the ratio of momentum diffusion by the Lorentz force to inertia for the large scales.

### 31 May 2013, Erfolgreich in der interkulturellen Kommunikation. Eine Einführung

Sabine Vana-Ströhla,

INTERKULTURELLES TRAINING

SABINE VANA

**Erfolgreich in der interkulturellen Kommunikation. Eine Einführung**

### 28 May 2013, Simulation-Driven Product Design

Dr. Wolfgang Bauer

ANSYS Germany GmbH

**Simulation-Driven Product Design**

**Abstract:**Simulation-Driven Product Development takes engineering simulation to another level ― the unequalled depth and breadth coupled with its unmatched engineered scalability, comprehensive multiphysics foundation and adaptive architecture set ANSYS technology apart. These ANSYS Advantages add value to the engineering design process by delivering efficiency, driving innovation and reducing physical constraints, enabling simulated tests that might not be possible otherwise.

The increasing demand in predictive capabilities of engineering software requires a highly skilled engineer. A proper quality assurance of the simulation process puts strong demands on careful validation. The co-operation with research institutes plays an important role to further evolve the simulation technologies. This will be illustrated by means of examples.

### 23 April 2013, Computer simulations for crystal growth in photovoltaic industry

cancelled!

Dr. Maksims Kirpo

Bosch AG

**Computer simulations for crystal growth in photovoltaic industry**

**Abstract:**

The current technology for growth of Si crystals for photovoltaic crystals will be shortly discussed but the talk will be mainly focused on Czochralski (Cz) process. Current advances in global computer simulation of Cz crystal growth will be demonstrated comparing possibilities and results of the available specialized commercial software and self developed simulation approach based on ANSYS FLUENT. Future trends in the development of computer simulations for crystal growth will be sketched.

### 09 April 2013, Liquid metal experiments with strong magnetic fields and high electrical currents

Martin Seilmayer

Helmholtz-Zentrum Dresden Rossendorf

**Liquid metal experiments with strong magnetic fields and high electrical currents**

**Abstract:**

To measure the fluid motion in liquid metal experiments Ultrasound Doppler Velocimetry (UDV) is used very often. The very small UDV signals can be disturbed by high direct current sources due to electromagnetic noise coming from these devices. The presentation will give some ideas and work around to common problems arising with magnetic field generation. All this will be explained on an ongoing experiment to the magneto rotatorical instability (MRI) in our laboratory. Finally some concepts and results will be given to rise measurement quality.

### 29 Jan 2013, Modeling of Multiscale and Multiphase Phenomena in MaterialS Processing

Andreas Ludwig, Abdellah Kharicha, Menghuai Wu

University of Leoben, Department Metallurgy,

Franz-Josef-Strasse 18, 8200 Leoben, Austria

**Modeling of Multiscale and Multiphase Phenomena in MaterialS Processing**

**Abstract**

In order to demonstrate how CFD can help scientists and engineers to better understand the fundamentals of engineering processes, a number of examples are shown and discussed. The paper covers (i) special aspects of continuous casting of steel including turbulence, motion and entrapment of non-metallic inclusions, and impact of softreduction; (ii) multiple flow phenomena and multiscale aspects during casting of large ingots including flow induced columnar-to-equiaxed transition and 3D formation of channel segregation; (iii) multiphase magneto-hydrodynamics during electro-slag remelting; and (iv) melt flow and solidification of thin but large centrifugal castings.

### 29 Jan 2013, TRIP-Matrix-Composites: Fundamental aspects and process modeling

Prof. Dr.-Ing. Rüdiger Schwarze

Institut für Mechanik und Fluiddynamik

TU Bergakademie Freiberg

**TRIP-Matrix-Composites: Fundamental aspects and process modeling**

**Abstract:**

TRIP-Matrix-Composites are composite materials made of TRIP steel and partially stabilized zirconium dioxide with low density, with high strength and high energy absorption capability. They are produced in casting operations, in spray processes or by sintering of metal and ceramic powders.

In the presentation, fundamental aspects of TRIP-Matrix-Composites are explained. First results of CFD simulations for the liquid process routes are presented. Open questions and topics of future work are discussed.

### 22 Jan 2013, Perspektiven für eine Vollversorgung mit erneuerbaren Energien

Prof. Beckmann

TU Dresden

**Perspektiven für eine Vollversorgung mit erneuerbaren Energien**

# 2012

### 11 Dec 2012, Model Optimization using Graph Rewriting

Ekaterina Pacholik,

TU Ilmenau

**Model Optimization using Graph Rewriting**

### 06 Dec 2012, Superconductivity at room temperature: Science or Fiction?

Prof. Esquinazi,

Universität Leipzig

**Superconductivity at room temperature: Science or Fiction?**

### 30 Oct 2012, Development and Implementation of a measurement method for determining the bending stiffness of carpal vibrissae of rats

Monika Haase,

TU Ilmenau

**Development and Implementation of a measurement method for determiningthe bending stiffness of carpal vibrissae of rats**

**Abstract:**

The tactile hairs are presented in almost all rodent animals. The implementation of the biological model into a technical development enables machines to recognize and analyze an unknown environment. Basis for the use in technology is the structural und functional analysis of the biological material. In this study different mechanical fixations were analysed to ensure reproducible und non-destructible research. With the ideal fixation the bending stiffness and bending line from carpal vibrissae were ascertained.

### 17 July 2012, "Optimizing Multiple Objectives" and "Introduction to Combinatorial Optimization"

Prof. Dr. Gabriele Eichfelder, Priv.-Doz. Dr. Regina Hildenbrandt

FG Mathematical Methods of Operations Research

Institute of Mathematics

Ilmenau University of Technology

**"Optimizing Multiple Objectives" and "Introduction to Combinatorial Optimization"**

**Abstract:**

The first part of this talk intends to be an introduction to the modeling of continuous optimization problems and the challenges which arise in solving them. In addition to that, optimization problems with multiple objective functions, which have to be optimized simultaneously, are introduced.

The second part of the talk gives a short introduction to combinatorial optimization and how such problems can be treated numerically.

### 16 July 2012, Regenerative Gaskreisprozesse zur dezentralen Energiewandlung

Hans-Detlev Kühl

Lehrstuhl für Thermodynamik

TU Dortmund

**Regenerative Gaskreisprozesse zur dezentralen Energiewandlung**

**Abstract:**

In dem Vortag wird eine systematische Übersicht über regenerative Gaskreisprozesse zur dezentralen Energiewandlung gegeben. Dabei wird auf bisherige Projekte und Entwicklungen eingegangen. Die am Lehrstuhl für Thermodynamik der TU Dortmund vorhandene Vuilleumiermaschine wird vorgestellt. Die Ergebnisse eines von der DFG geförderten Mikro-KWK-Wärmepumpenprojektes werden präsentiert.

### 10 July 2012, Experimental and Numerical Investigations of coupled electromagnetic and aerothermodynamics phenomena in an electrical contactor

Malik Al-Amayreh

Lehrstuhl für Strömungsmechanik

Technische Fakultät

Friedrich-Alexander Universität Erlangen-Nürenberg**Experimental and Numerical Investigations of coupled electromagnetic and aerothermodynamics phenomena in an electrical contactor**

**Abstract:**

A new blowout technique to control the speed and the direction of the flow has been introduced and shown to decrease the burning time of the electrode material. The breaker chamber used consists of five electrodes: two anodes, two cathodes and a moving electrode or bridge which works as an anode and a cathode simultaneously. Two permanent magnets and two coils installed near the electrodes have been used in order to generate magnetic forces. With this new blowout technique, the ionized gases generated between the electrodes feed the coils with current. The velocity of the ionized gases increases if more current is allocated in the arc plasma. Hence the burning time of the ionized gases and thermal stress of the hot ionized gases on the materials of the electrodes are decreased.

In addition, the movement of the flow field of the ionized gases with an external magnetic field was analyzed using two optical methods, namely an optical imaging method and using a high-speed camera. Optical imaging software was developed to generate dynamic images of the high-speed ionized gases at a rate of 50,000 frames/s. The results of this method were compared with those obtained using a high-speed camera. The finite volume method was used to develop a transient numerical model of the ionized gas flow field inside the breaking chamber for the case of a DC current. The properties of the air plasma are considered variable with temperature and pressure.

### 03 July 2012, Instabilities and transport in MHD duct and channel flows - the recent computational results

Oleg Zikanov

University of Michigan

Dearborn, USA

**Instabilities and transport in MHD duct and channel flows - the recent computational results**

**Abstract:**

Results of recent computational studies of magnetohydrodynamic flows in a toroidal duct and a channel are presented. For the duct, we consider the case of high Hartmann number and the geometry of the 2004 experiment of Moresco and Alboussiere and show that turbulence appears near the outer wall at much lower Reynolds number than the number deteced in the experiments as corresponding to transition in Hartmann layers. For the channel, we analyze the transport of passive scalar at various orientations of the imposed magnetic field.

### 26 June 2012, Deep Brain Stimulation using Magnetic Fields

David Jiles

Department of Electrical & Computer Engineering

Iowa State University

Ames, Iowa, USA

**Deep Brain Stimulation using Magnetic Fields**

**Abstract:**

New applications for transcranial magnetic stimulation (TMS) are developing rapidly for both diagnostic and therapeutic purposes. Therefore so is the demand for improved performance, particularly in terms of their ability to stimulate deeper regions of the brain and to do so selectively. The coil designs that are used presently are limited in their ability to stimulate the brain at depth and with high spatial focality. Consequently any improvement in coil performance would have a signifcant impact in extending the usefulness of TMS in both clinical applications and academic research studies. New and improved coil designs have then been developed, modeled and tested as a result of this work. A large magnetizing coil, 300mm in diameter and compatible with a commercial TMS system has been constructed to determine its feasibility for use as a deep brain stimulator. The results of this work have suggested directions that could be pursued in order to further improve the coil designs.

### 19 June 2012, Dynamics of a drop in a Faraday experiment : the path-memory effect

Maurice Rossi

Institut Jean Le Rond d'Alembert

CNRS- Universite Paris VI

**Dynamics of a drop in a Faraday experiment : the path-memory effect**

**Abstract:**

Based on an experimental idea due to Y.Couder, I will present some aspects of the rich dynamics of a small drop levitating above a liquid layer which is itself oscillated. This drop engenders waves on the liquid layer that, in turn, may cause the motion of the drop in the horizontal plane. Model, numerics as well experimental investigations will be introduced and discussed leading to the idea of a path-memory effect !

### 14 June 2012, Role of large scale structures in instabilities and turbulence

Mahendra K. Verma

Physics Department

Indian Institute of Technology

Kanpur, India

**Role of large scale structures in instabilities and turbulence**

Abstract:

In basic instability analysis, we typically study the growth of the primary mode. The saturation of the growth, secondary instabilities, and pattern formation are due to secondary modes. The nonlinear dynamics of the large-scale primary and secondary modes are very interesting. We will present some of the recent work on the same for Rayleigh Benard convection.

It has also been observed in experiments and numerical simulations that the imprints of the large-scale modes are present even when the flow has become fully turbulent. One such phenomenon is flow reversals in turbulent convection. We will show in that the large-scale fields play a major role in this dynamics. Such features are also observed in magnetic field reversals of dynamo.

### 12 June 2012, High Temperature Superconductors – State of the Art and Innovative Applications

Dr. Frank Werfel

Adelwitz Technologiezentrum GmbH (ATZ)

Adelwitz, Germany

**High Temperature Superconductors – State of the Art and Innovative Applications**

**Abstract:**

After the discovery of superconductivity a century ago by Kamerlingh Onnes at the University of Leiden in the next fifty years most of the research was directed at identifying the mechanism and the exotic electric and magnetic properties. However, the highest detected materials critical temperature with 23.2 K (Nb3Ge) was low. This situation changed completely after the High-Tc superconductor (HTS) discovery hype in 1986/87 having a Tc above the LN2 temperature and generate large expectations in solid state physics and electric applications. With MgB2 and Iron - Pnictides (Tc =39 K; 55 K) further superconductor materials entered the HTS family after 2000 which are presently under careful investigation. Due to significant material improvements of the REBCO (Tc = 92 K) and BiSCCO (Tc = 90 K; 110 K) superconductor families a great potential in power energy systems become visible. High-Tc superconductors can contribute to energy efficiency, primarily reducing the dissipation and losses in electric machines, motors and generators, magnetic bearings and flywheels, in electric grids and transportation. The progress of HTS conductor science and of technological engineering is basic for larger and robust energy power devices like superconducting cables and wind power generators in MW scale. Magnetic levitation with bulk superconductors has been widely tested and evaluated as rotational bearings for flywheel stabilization and linear transport systems. Basically, HTS applications show three advantages compared to conventional solutions: Smaller, lightweight and more efficient. High-Tc superconductors (HTS) possess superior physical and technical properties although the superconducting mechanism is still in the dark. We survey the HTS physics briefly and scan the technology status of superconducting systems like cable, motor/generator, fault current limiter, and energy storage components for their potential of large-scale commercialization. We report about a 10 kWh / 250 kW flywheel with magnetic stabilization of the rotor. Effort is being made in the development of mobile HTS magnetic levitation (Maglev) devices. We have designed and produced advanced bulk cryostats operating now in China, Brazil and Germany. We conclude that a broad range of intensive research and development in energy power systems is still needed to produce technological options that can allow and contribute both to climate stabilization and to economic development.

### 05 June 2012, The electronic kilogram - the past, the present, and the future

Stephan Schlamminger

National Institute of Standards and Technology

Gaithersburg, MD, USA

**The electronic kilogram -- the past, the present, and the future**

**Abstract:**

The kilogram is the unit of mass in the international systems of units (SI). It is still defined by an artifact that is kept in a vault outside Paris. In recent years the idea of redefining the SI has gained some traction and a redefinition of the SI can become reality within a few years.

In the new SI, seven reference constants will be defined with fixed values and zero uncertainties. All units will be realized using these constants. The unit of mass will be linked to the Planck constant, h. One way to realize the mass is with a device called a watt balance. The watt balance compares mechanical power, lifting a mass in the gravitational field of the earth, to electrical power, which can be measured as the product of h, two frequencies and a known multiplier.

### 29 May 2012, GPU simulations for the Boltzmann equation

Stefan Brechtken

Arbeitsgruppe Numerische Mathematik

und Informationsverarbeitung,

TU Ilmenau

**GPU simulations for the Boltzmann equation**

**Abstract:**

- The numerics of the Boltzmann equation

- Introduction to NVIDIA graphic card architecture and GPU parallelization

- Efficieny comparison: GPU vs. CPU

- Physical phenomena of the Boltzmann equation

- Parallelization strategies for GPUs

### 03 April 2012, Some work on Doppler global velocimetry

**Some work on Doppler global velocimetry**

Prof. Zhang Hongjun

China Jiliang University

Hangzhou

### 24 Jan 2012, Modelling and Simulation of Electrosimulating Implants in Biosystems

**Modelling and Simulation of Electrosimulating Implants in Biosystems**

Prof. Dr. Ursula van Rienen,

Universität Rostock

**Abstract**

Electrically stimulating implants are designed to restore body functions that have been restricted by illness, accident or age. Best known is the pacemaker, but also the deep brain stimulation ("brain pacemaker"), cochlear implants or entirely new implants are examples for this. Their interaction with the biological system has to be considered for an optimal design. In addition to experiments,simulations are of central importance. Here it is necessary to take all important aspects into account within the simulation models.

The modeling and simulation of electrically stimulating implants comprises a series of challenges. The first and most important challenge lies in the strong interdisciplinary nature which needs to be handled. Then follow the multi-scale character, integrating some very poor data situation regarding electrical tissue properties, or the need to model microscopic electrochemical processes in a hybrid model among other aspects.

In the presentation, some of these aspects will be illuminated and some initial solutions in the context of the DFG RTG 1505/1 "welisa" will be described.

### 10 Jan 2012, Rotating-stratified turbulence: experiments and simulations

**Rotating-stratified turbulence: experiments and simulations**

Dr. Peter Davidson,

University of Cambridge

**Abstract**

Turbulence evolving in a rapidly rotating environment is known to be dominated by large, long-lived, columnar vorticies aligned with the rotation axis. These vortices are observed to be prodominantly cyclonic and they dominate the dispersion and decay characteristics of the turbulence. There is no general agreement as to how these vortices form, nor any convincing argument as to why cyclones dominate over anti-cyclones. One possible formation mechanism is presented, and speculative comments provided on the dominance of cyclones. Stratified turbulence is also discussed, where the dominant stuctures are large, flat, pancake-like eddies.

# 2011

### 08 Nov 2011, CUPS & V2G - elements of the Smart Grid

**CUPS & V2G - elements of the Smart Grid**

Univ. Prof. Ph.D. D.Sc. Grzegorz Benysek

University of Zielona Góra

Institute of Electrical Engineering

**Schedule:**

Introduction

SmartGrid – the concept

CUPS – solutions to selected problems of T&D

V2G – solution to selected problems of T&D

Conclusions

**Synopsis:**

Over the last few years, electrical energy consumption has continually grown and, at the same time, investment in the T&D (Transmission and Distribution) infrastructure has correspondingly declined. Traditional solutions for upgrading the electrical system infrastructure have been primarily in the form of new power plants, new transmission lines, substations, and associated equipment. However, as experience has proven, the process of authorizing, locating, and constructing new transmission lines has become extremely difficult, expensive and time-consuming. As a result, the power grid is under stress, resulting in compromised reliability and higher energy costs.

Despite the above problems, system reliability is vital and cannot be compromised. To overcome this problem, grid operators are moving away from radial systems towards networked; however this degrades controllability of the network because current flows along particular lines which cannot easily be controlled. The situation is even worse if an incident such as loss of a line results in overload, increasing the possibility of a blackout. Additionally, rapid load growth leads to jamming on key lines which, in consequence, leads to an inefficient operation of energy markets.

The answer seems to lie in transforming the current EPS (Electrical Power System) into SmartGrid. Future grids (SmartGrid) will be strong, more flexible, reliable, self-healing, fully controllable, asset efficient and will be a platform to make possible the coexistence of smart-self-controlling grids with great numbers of DGs (Distributed Generation) and large-scale centralized power plants. The need for modifications, demands to remove the barriers to the large-scale exploitation and integration of DGs and other players, will necessitate research and development new innovative technologies from generation, transmission and distribution to communication tools, with far more sensors than at present. Thus it is envisaged that FACTS (Flexible AC Transmission Systems), CUPS (Custom Power Systems), ESS (Energy Storage Systems), DG, V2G (Vehicle to Grid), smart end-user appliances together with communications will be at the heart of the future SmartGrid.

SmartGrid will allow the customer to take an active role in the supply of electricity, which can help the electricity system respond to equipment failures, weather-related emergencies, and other conditions. At present, the system operator must maintain enough excess generating capacity online or quickly available to continue supplying system load if a large generating unit or transmission line fails. In SmartGrid, much of that reserve could be provided by EPS or small DG, ESS units located near end-user sites.

Summarizing, a modernized SmartGrid would create EPS that:

- Will reduce peak loads and generate reserve margins;
- Will delete capital costs of new T&D infrastructure as well as generating plants;
- Will lower T&D line losses together with operation and maintenance costs;
- Will redirect power flows, change load patterns, improve voltage profiles and stability;
- Will enable loads ESS and DG to participate in system operations;
- Through extensive monitoring, quick communications, and feedback control of operations, will have much more information about system rising problems before they affect service;
- Provide system utilities with advanced visualization tools to enhance their ability to oversee the system.

The proposed lecture arises from conviction that it is necessary to re-think the basic philosophy governing the electricity distribution systems. In author’s opinion there is need to fully exploit the potential advantages of renewable energy sources and distributed generation which should not only be connected, but also fully integrated into the distribution system just to increase the efficiency, flexibility, safety, reliability and quality of the electricity and networks. For that reason transformation the current electricity grids into a SmartGrid (resilient and interactive) necessitate the development, propagation and demonstration of key enabling cost competitive technologies (e.g. innovative interconnection solutions, storage technologies for renewable energy sources, power electronics etc.).

On the base of above the major aim of this lecture is to present the features, solutions and applications of the power electronics arrangements useful in future smart electrical energy networks.

### 26 Oct 2011, Actions of electromagnetic field with liquid silicon

**Actions of electromagnetic field with liquid silicon**

Fatoumata Santara

Part 1: Electromagnetic retention and electromagnetic stirring

Part 2: Influence of electromagnetic stirring on the segregation of impurities

Part 3: Traveling and rotating electromagnetic field / Conclusion

**Abstract**

The presentation is related to the improvement of the segregation of impurities during the crystallization of solar grade silicon. The silicon feedstock has known composition of impurities. The objective is to decrease the concentration of these impurities in the crystallized silicon thanks to a turbulent stirring created inductively by an alternative magnetic field. Optimized experimental configuration was achieved after several calculations and experiments. The turbulent flow homogenizes impurities in the liquid silicon, improving the effective segregation coefficient. The chemical analysis of samples shows that the electromagnetic stirring is efficient because the concentration of Phosphorous impurity was reduced from 6 to 1.7 ppm during the crystallization, which is difficult to achieve for this impurity.

### 25 Oct 2011, ADVANCED METHODS IN COMPUTER SIMULATION AND 3D MODELING OF THE ORIGINAL PATENTS OF NIKOLA TESLA

**ADVANCED METHODS IN COMPUTER SIMULATION AND 3D MODELING OF THE ORIGINAL PATENTS OF NIKOLA TESLA**

Dr. Vladan Vuckovic,

Faculty of Electronic Engineering

University of Nis, Serbia

**Abstract**

This lecture is an excerpt from the interim report on the work at the Technology Project "Computer Simulation and 3D Modeling of the Original Patents of Nikola Tesla" concerning research results achieved in the period from 2009 to the end of 2010. The project was supported and financed by the Ministry of Science and Technological Development of Serbia in the period 1.4.2009-31.3.2010, with an extension to December 31, 2010, with a participation of the Museum Nikola Tesla in Belgrade, Serbia. The lecture presents details of the 12 patents of Nikola Tesla patented from 1888 to 1914 that was a subject of 3D modeling and simulation within the project in the considered period. For each of these patents project details will be shown. Also, 3d models and simulation of some complex Tesla's experiments as well as his two main laboratories in Colorado Springs and Long Island will also be noticed. In this way, our work can be viewed as the beginning of the virtual foundation of Tesla's patents and his main ideas.

### 18 Oct 2011, Numerical Analysis of Singularly Perturbed Time-Dependent Semilinear Reaction-Diusion Problems

**Numerical Analysis of Singularly Perturbed Time-Dependent Semilinear Reaction-Diusion Problems**

Simona-Blanca Savescu

Berlin

Abstract

I consider time-dependent semilinear singularly perturbed reaction-diusion problems with Dirichlet and Neumann boundary conditions under considerably less restrictive assumptions than usual. By perturbing the asymptotic expansion, I derive boundary, initial and corner layer functions, determine their exact exponential decay rate and construct discrete upper and lower solutions, then I estimate the truncation error in the discrete upper solution.

As the conventional implicit method might produce incorrect and unstable computed solutions on uniform meshes, I introduce a stabilization method and prescribe a choice of the stabilization parameter that ensures uniqueness of the computed solution. The numerical results suggest that under this choice, switching to the stabilized method cures the instability and yields qualitatively correct computed solutions on any mesh. I investigate the two methods on layer-adapted meshes of Bakhvalov and Shishkin types and establish second order uniform convergence in the discrete maximum norm - in the case of Shishkin mesh, up to a logarithmic factor.

### 11 Oct 2011, COLD CRUCIBLE INDUCTION MELTING: A Versatile Technology

**COLD CRUCIBLE INDUCTION MELTING:A Versatile Technology**

Dr. Sugilal Gopalakrishnan

Bhabha Atomic Research Centre

Mumbai-400085, INDIA

Abstract

Cold crucible induction melting (CCIM) technology is an advanced technology which is being used for a variety of applications. The CCIM process, also known as Induction Skull Melting (ISM) process, is widely used to produce high purity melts of a range of difficult to melt materials, including Ti-Al alloys for aerospace applications, high temperature superconducting materials and silicon for electronic applications, corium (a mixture of UO2 and ZrO2) for nuclear reactor applications, glasses and ceramics for nuclear waste immobilization etc. High temperature availability and high purity are the key features of the CCIM process.

In cold crucible induction melting, material is directly heated by electromagnetic induction employing a segmented crucible which is manufactured from contiguous segments forming a cylindrical volume, but separated by a thin layer of electrically insulating material. An inductor surrounding the segmented crucible induces eddy currents in each segment of the crucible. By virtue of its sectorised structure, the crucible is largely transparent to the induced magnetic field and thereby, directly heats the process material inside the crucible by induction. The segmented crucible is cooled by circulating water internally and hence the name "cold crucible".

In cold crucible induction melter, convection currents in the melt are governed either by gravitational body forces or electromagnetic body forces depending upon the electrical conductivity of the material to be melted. Typically, the gravitational body forces govern natural convection in oxide melts (poorly conducting) and Lorentz forces in metal melts (highly conducting). Moreover, the Lorentz forces partially levitate the metal melt depending up on the frequency and power of the induction heating.

Since the physical phenomena taking place in a cold crucible induction melter are highly complex and strongly inter-related, mathematical modeling is generally used for the design and analysis of such systems. Numerical solution of Navier-Stokes equations and Maxwell's equations are often employed for predicting the melt conditions.

The lecture focuses on various aspects of cold crucible induction melting - ranging from concepts to applications.

### 04 Oct 2011, Large-scale patterns in transitional plane Couette flow

**Large-scale patterns in transitional plane Couette flow**

Dr. Yohann Duguet,

LIMSI-CNRS,

Orsay, France

Abstract

Plane Couette flow is the simplest flow prototype for subcritical transition to turbulence in wall-bounded shear flows. Yet, despite the simplicity of the set-up the onset of transition in this flow is characterised by poorly understood large-scale patterns of alternate turbulent and laminar-like zones. I will first show recent numerical simulations of this phenomenon in extended domains, with a focus on the physical mechanisms at play. In a second part I will show how these patterns can evolve under the influence of either spanwise rotation or of an imposed spanwise magnetic field.

### 12 July 2011, MAGNETIC MATERIALS IN SUSTAINABLE ENERGY

Oliver Gutfleisch

Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden),

Institute for Metallic Materials,

P.O. Box 270016,

D-01171 Dresden, Germany

**MAGNETIC MATERIALS IN SUSTAINABLE ENERGY**

Abstract

A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research in energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conversion and transportation. Magnetic materials are essential components of energy applications (i.e. motors, generators, transformers, actuators, etc.) and improvements in magnetic materials will have significant impact in this area, on par with many "hot" energy materials efforts (e.g. hydrogen storage, batteries, thermoelectrics, etc.).

The lecture focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, will be discussed.

The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, will be examined in the context of their respective markets as well as their potential impact on energy efficiency. Finally, considering future bottle-necks in raw materials and in the supply chain, options for recycling of rare-earth metals will be analysed.

*O. Gutfleisch, J.P. Liu, M. Willard, E. Brück, C. Chen, S.G. Shankar, Magnetic Materials and Devices for the 21 ^{st} Century: Stronger, Lighter, and More Energy Efficient (review), Adv. Mat. 23 (2011) 821-842.*

### 23 June 2011, Towards the next generation on surface biomedical electrodes

Prof. Carlos Fonseca

Universität Porto

Portugal

**Towards the next generation on surface biomedical electrodes**

### 17 June 2011, Detection of Surface Stress and Hardness in Ground Steel Components using Magnetic Barkhausen Measurements

D.C. Jiles

Department of Electrical & Computer Engineering

Iowa State University, Ames, Iowa 50011, USA

and

Wolfson Centre for Magnetics, School of Engineering

Cardiff University, Cardiff CF24 3AA, UK

**Detection of Surface Stress and Hardness in Ground Steel Components using Magnetic Barkhausen Measurements**

Abstract

The developments of theoretical models have been crucial to the understanding of the complex relationships between magnetic measurements and materials conditions including microstructure and stress state. Recently a model of the Barkhausen effect has been extended to deal with more advanced stochastic domain wall dynamics and the dependence on microstructure. Model equations of the magnetomechanical effect have been improved for better quantitative description of the effects of stress on magnetic properties and this has been extended to include description of the stochastic process aspects of the Barkhausen effect. Only in this way has it been possible to make serious advances in the interpretation of Barkhausen effect measurements and their practical application. Advances in magnetic measurement methods have resulted in the construction of equipment for surface condition assessment based on the detection and analysis of Barkhausen emissions. This has been applied to the problem of non-destructive testing of helicopter main rotor gears.

### 14 June 2011, Radial spreading and stability of thin films

Konrad Boettcher

Fluid Mechanics

TU Dortmund

**Radial spreading and stability of thin films**

Abstract

Thin-film flows are involved in many coating processes, where it is often desirable to achieve thin and homogeneous fluid layers. In the present investigations, we treat droplets spreading on rotating solid substrates. Micro-scale effects appear, firstly, on the wetting front, where the film height tends to zero. Secondly, micro-scale effects may appear at other locations, where the free liquid/gas interface approaches the solid substrate, as e.g. at film rupture. For such situations, molecular effects need to be considered, e.g. in form of the disjoining pressure, to get physically-correct solutions. Otherwise, the spreading can be modeled within the frame of continuum mechanics, augmented by the (empirical) law of Tanner to capture the contact line dynamics.

The lecture presents, on the one hand, an overview of several interesting issues, as (i) spreading with and without considering the disjoining pressure, (ii) spreading after central rupture, including hysteresis effects, and (iii) non-isothermal spreading, including temperature-dependent surface tension (Marangoni effect) and temperature-dependent density (Rayleigh-Bénard effect). On the other hand, we present results for the instability of the contact line, for which the contact line gets corrugated, for isothermal conditions. This instability goes along with a transition from (axially-symmetric) two-dimensional to three-dimensional behaviour. Furthermore we investigate the stability of the developing non-isothermal eddies.

### 17 May 2011, Impact of magnetohydrodynamics on the development of liquid metal blankets for fusion reactors

Leo Bühler

Institut für Kern- und Energietechnik (IKET)

Karlsruhe

**Impact of magnetohydrodynamics on the development of liquid metal blankets for fusion reactors**

Abstract

Research on development of liquid-metal blankets for fusion reactors has led to a variety of design ideas over the past decades. A key issue for reliable concepts is the accurate prediction of magnetohydrodynamic flows. The latter ones are established as a result of the interaction of the electrically conducting breeder or coolant, which is circulated in the blanket, with the intense plasma-confining magnetic field. The strong magnetohydrodynamic phenomenaplay a decisive rolein the definition of the thermo-mechanical layout of a liquid metal blanket.Several smart designs had to be essentially modified or even abolished after a thorough MHD analysis. Major previous ideas in blanket engineering are shortly reviewed and the focus is then placed on the helium cooled lithium lead blanket which is the European candidate for a liquid metal test blanket in the International Thermonuclear Experimental Reactor (ITER). The requirements for numerical predictions of MHD flows in liquid-metal blankets and the current status of experimental research for fusion technology applications are discussed.

### 03 May 2011, Fusing computational and experimental flow data with Gappy POD

Stefan Görtz

Deutsches Zentrum für Luft- und Raumfahrt e. V.

in der Helmholtz-Gemeinschaft

Institut für Aerodynamik und Strömungstechnik

C²A²S²E Center for Computer Applications in AeroSpace Science and Engineering

**Fusing computational and experimental flow data with Gappy POD**

Abstract

Gappy Proper Orthogonal Decomposition (POD) is a simple but powerful method for data fusion and offers efficient means to harmonize data, i.e. improve the consistency between various sets of data. The basic idea behind Gappy POD for data fusion is that the POD analysis of computational flow solutions at different flow conditions yields a set of empirical modes, which describes the dominant behavior or dynamics of a given flow problem in an optimal sense, i.e. for any given basis size, the error between the original and reconstructed data is minimized. Given a suitable set of POD modes derived from computational data, the Gappy POD solves a small and thus inexpensive least squares problem to determine a set of coefficients such that the reconstruction (linear combination of modes) optimally matches the experimental data. Besides its capability to harmonize data, the Gappy POD approach offers additional benefits, such as the prediction of quantities that were not measured experimentally. It can also be seen as a way to correct complete numerical flow solutions if limited experimental data is available. The lecture will present the Gappy POD in the context of aircraft aerodynamics and Particle Image Velocimetry (PIV).

### 05 April 2011, High Performance Computing

Heiko Jörg Schick

IBM Deutschland

**High Performance Computing**

### 01 Feb 2011, Listening to the Universe with Einstein's Gravitational Waves

Prof. Dr. Karsten Danzmann

Direktor, Albert-Einstein-Institut Hannover

Max-Planck-Institut fuer Gravitationsphysik und Leibniz Universitaet Hannover, Germany

**Listening to the Universe with Einstein's Gravitational Waves**

**Abstract**

Can we hear the Universe? At first sight that doesn't make sense as there is no air in outer space and sound cannot propagate. But more than 90 years ago Einstein predicted a different kind of waves, Gravitational Waves, as a consequence of his General Theory of Relativity. Gravitational Waves are small distortions of space itself that are emitted by all accelerated masses and propagate with the speed of light. They have never been directly detected, but several kilometer-size laser-interferometric detectors are currently searching for them from the ground. They will soon be complemented by space-based detectors with armlengths of millions of kilometers. Astrophysical sources for these waves are coalescing binary stars, supernovae, Black Holes and the Big Bang.

# 2010

### 30 Nov 2010, Magnetoresistivity – an Old Topic of Current Importance

Prof. Dr. U. Hartmann

Experimental Physics Department Saarland University

**Magnetoresistivity – an Old Topic of Current Importance**

**Abstract**

Magnetoresistivity is a phenomenon which results in a change of the electrical conductivity ofa conductor upon the application of an external magnetic field. This phenomenon wasdiscovered in 1857 by Lord Kelvin. It took a very long time until magnetoresistivity could atleast partly been explained in terms of quantum mechanical arguments. Today we know thatthere is a whole family of different mechanisms which could lead to a magnetoresistivebehavior. In any case the interplay between electronic charges and spins plays a crucial role,and thus magnetoresitive effects are an important basis of spin-based electronics andinformation technology, i. e., of spintronics.The lecture introduces into the basic fundamentals of the interplay between electron spin andcharge in ferromagnetic materials and gives an overview over technically importantmagnetoresistive effects. In particular the “Giant Magnetoimpedance Effect”, which was onlyfound recently, will be discussed and a presentation of contributions made by SaarlandUniversity will be given.

### 16 Nov 2010, Flowmeter calibration and traceability

Dr.-Ing. Rainer Engel

PTB Physikalisch-Technische Bundesanstalt Braunschweig

Department Liquid Flow

Head of the Working Group ”Traceability in liquid flow measurement”

**Flowmeter calibration and traceability**

**Abstract**

As an introduction, an overview is given how flowmeters and their operation can be characterized: operation principles, general design and makes. The measurement characteristics of flowmeters are quantitatively described by means of error curves which represent diagrams that display meter reading errors versus flowrates.

As a systematic overview, the several principles of liquid flowmeter calibration facilities and examples of their technical realizations are presented. On the basis of a comprehensive model of the measurement process, the measurement uncertainty model of flow standard facilities is derived and the impacts of the dominating sources of uncertainty are analyzed.

Like in other fields of metrology, fluid flow metering has to be traced back to the respective national flow standard facilities of the NMIs (**n**ational **m**etrology **i**nstitutes). Unlike to other fields of metrology, generally, flow metering devices provide comparatively “poor” accuracy capabilities, i.e. the low measurement uncertainties, documented as the CMC entries (**c**alibration and **m**easurement **c**apabilities) by the national accreditation bodies, cannot be proven directly by flowmeter-based traceability measurements. So a practice is generally applied which relies on an element-by-element traceability approach (via mass, density, temperature, and time measurements). However, this approach ignores the fact that, additionally to the components of the derived units of fluid flow, mentioned above, other dynamic effects in the measurement processes increase the measurement uncertainties.

**References**

[2] Engel, R., Baade, H.-J., Model-based flow diverter analysis for an improved uncertainty

determination in liquid flow calibration facilities, *Measurement Science and Technology*, 21 (2010),

11pp), 2010.

[http://iopscience.iop.org/0957-0233/21/2/025401]

[3] Engel, R., Baade, H.-J., Water density determination in high-accuracy flowmeter calibration-

Measurement uncertainties and practical aspects,* Conference Proceedings*, 15^{th} Flow Measurement

Conference(FLOMEKO), Taipei, Taiwan, October 13 – 15, 2010

### 19 Oct 2010, Anisotropy Modeling for Computational Simulations of Turbulent Flows

Dr. Peter Hamlington

Naval Research Laboratory, Washington DC, USA

**Anisotropy Modeling for Computational Simulations of Turbulent Flows**

**Abstract**

The wide range of space and time scales associated with high Reynolds number turbulence introduces substantial complexity in computational simulations of practical turbulent flow problems. As a result, most

such simulations are aimed simply at capturing the evolution of the mean flow through solution of the Reynolds averaged Navier-Stokes equations. Obtaining a closed set of equations using this approach,

however, requires a physically accurate model for the turbulence anisotropy. Here we review the challenges associated with modeling the anisotropy, and outline a rational framework for understanding the large number of existing models based on their nonlinear, nonequilibrium, and nonlocal properties. This framework clarifies the physics underlying each model, allows the suitability of a model for a particular application to be assessed, and provides direction in the development of new models. Finally, an outlook is provided on the future of anisotropy modeling in turbulence simulations.

### 01 June 2010, Magnetoelectrochemistry

# Frau Dr. Margitta Uhlemann

Dept. Electrochemical Properties of Functional Materials

Institute for Metallic Materials

Leibniz-Institute for Solid State and Materials Research (IFW) Dresden

**Magnetoelectrochemistry**

The effect of magnetic fields on electrochemical processes is an important branch of electrochemistry, which has been a matter of interest for more then three decades. The so called magnetoelectrochemistry covers redox processes, metal deposition and corrosion as well as gas evolution processes.

Superimposition of the magnetic field especially during the electrodeposition process can introduce significant changes in the deposition behaviour but it is also capable of influencing deposit properties significantly. Mainly the deposited layers have a better quality, i.e. lower roughness, they are more compact and the grains are smaller. The most established influence of the magnetic field on the electrodeposition is related to the Lorentz force (** F**L). This force acts in the hydrodynamic layer and is accepted as the main driving force of the so-called magnetohydrodynamic (MHD) effect. This force is maximal if the imposed field is oriented parallel to the electrode surface.

However, some microscopic effects mainly in perpendicular to the electrode oriented magnetic fields cannot be explained by the classical macroscopic MHD-effect. One explanation has been introduced based of the micro scale action of

*L, which causes micro-MHD flows in the vicinity of the electrode propagating to a macroscopic effect. Both the macroscopic and the microscopic MHD-effects have a strong impact on electrochemical gas evolution processes and lead to higher efficiency of the reaction and fast desorption of gas bubbles.*

**F**Although the MHD- effect is predominant in most electrochemical studies in magnetic fields

**L is not the only magnetically induced force. Especially in non-homogenous magnetic fields the field gradient force**

*F**v*

**F**_{}B was found to have remarkable influence as well. It depends on the magnetic flux density and its gradient, the molar magnetic susceptibility of all species as well as on their concentration. It will be shown that this force has an important impact on structuring deposition and corrosion processes.

### 11 May 2010, Ultrasound study of saturated porous material

#### Ultrasound study of saturated porous material

Josè Oskar Torres

Pontificia Catolica Universitad del Perù, Lima

The scientific motivation of this study is the validation of the poroelastic model, proposed by Biot, to calculate the ultrasonic wave propagation in a saturated porous material.

The model, based in two coupled equations coming from the solid and fluid stress - strain relation, predicts the propagation of two compression waves and one shear wave in the porous material. The study was centered in the compression waves only.

The practical motivation is to find an alternative to the X-ray method to characterize the shape of the human bones, and also to determinate its internal geometry, like the porosity for an osteoporosis analysis.

Sequences of experimental measurements were performed with in water saturated samples with several thickness made out of glass balls with different diameters (224 μm, 380 μm, 560 μm) but with the same physical properties. The responses of these samples were obtained using an ultrasonic signal at the frequencies of 0.5 MHz, 1 MHz and 2 MHz. The calculus of the attenuation and phase velocity of the two compression waves was done with the amplitude and phase of the Fourier transform of the measured signal.

The applicability of the model was achieved comparing these experimental acoustic parameters with the analytical prediction but without scattering phenomena.

Finally, a numerical implementation was done to have a better understanding of the physics involved.

### 27 April 2010, Hydrodynamic Instabilities in Liquid Layers

#### Hydrodynamic Instabilities in Liquid Layers

Michael Bestehorn

Lehrstuhl Theoretische Physik II

Brandenburgische Technische Universität

Cottbus

**Abstract**

The first part of the lecture gives an overview on macroscopic non-equilibrium spatialpatterns formed by instabilities of simpler homogeneous states. Special emphasis islayed on hydrodynamic convection instabilities, thermal or solutal. Part II outlinesthe basic methods developed for a theoretical description and gives a characterizationof several types of instabilities. Each type has its own “normal form” valid close tothreshold and shows different typical patterns. Part III is devoted to thin films witha free, deformable surface. Spinodal dewetting, coarsening, but also “running drops”can be studied in pure fluids and in mixtures.

### 13 April 2010, Non-Destructive Testing of Materials and Components

#### Non-Destructive Testing of Materials and Components

W. Arnold*

Department of Material Science and Technology, Saarland University

D-66123 Saarbruecken, Germany

Components and semi-finished products are often tested for quality assurance by non-destructive testing and evaluation (NDT&E) using ultrasonic, X-ray, eddy current thermal andmany other ndt-techniques. In ultrasonics, depending on the geometry and nature of thedefect, volume, surface and guided waves are employed. For the reception and evaluation ofthe ultrasound signals reflected by the flaws, synthetic aperture techniques, ALOK, phasedarray are applied in addition to the standard pulse-echo technique. Depending on theultrasound attenuation of the material to be investigated, defects can be detected down to thesub-millimeter regime.

This contribution discusses the physical bases of various ndt-techniques, in particularultrasonic techniques for different applications such as testing of pipelines, railway wheels,automotive components, ceramic implants, and electronic components. Furthermore,ultrasonic backscattering methods for the characterization of the microstructure of materials,e.g. measurement of the hardening depth in steel and sound-velocity measurements for thedetermination of mechanical stress are presented. Nonlinear effects in wave propagation formay be used for ndt purposes in future.

Ultrasound is combined with atomic force microscopy to achieve the lateral resolutionof scanning probes techniques for imaging. Images can be obtained with the contrastdepending on the local indentation modulus and Q-1 value, i.e. the internal friction with alateral resolution of about 10 nm.

The principles of the various ndt instruments are also discussed

This presentation is based on the work carried out at Fraunhofer Institute for Non-Destructive Testing (IZFP) in Saarbruecken, Germany, where the speaker worked untilretirement as department head. Many master and PhD students from the Saarland University,Department of Materials Science and Technology, and students and postdoctoral researchersfrom other universities and institutions have participated as well.

Present address: 1. Phys. Institut Universitaet Goettingen, Fritz-Hund Platz 1,D-37077 Goettingen, Germany

### 06 April 2010, The evaporatively driven cloud-top mixing layer

#### The evaporatively driven cloud-top mixing layer

Juan Pedro Mellado

RWTH Aachen University; Max Planck Institute for Meteorology

**Abstract**

Cloud parametrization remains one of the primary sources of uncertainty inlarge-scale studies of atmospheric flows, including climate research. And itstill constitutes a daunting task in spite of the advances in the field duringthe last decades. The realm of turbulence and clouds is immense: in thispresentation, we focus in one particular configuration, the cloud-top mixinglayer, and we cover different aspects of it . This system has been introduced inthe literature as a simplified surrogate to investigate, locally, particularphenomena occurring at the boundary between stratocumulus clouds and the uppercloud-free air. Evaporative cooling is the topic considered in this work. Themethodology, based on a two-fluid formulation, will be discussed first in orderto clearly set the context of the work. Then, a linear stability analysis willbe used to explain the unstable character of the equilibrium state under typicalatmospheric conditions (the so-called buoyancy reversal instability) and toidentify the two characteristic time scales of the system. The disparity ofthese two time scales will allow us to make certain conjectures about theturbulent behavior of the system, conjectures that will be confirmed later withdirect numerical simulations. The last part of the talk will focus on thecharacterization of this turbulent state, which turns out to be similar, to alarge extent, to free convection below a cold boundary.