Hochschulbibilographie

Anzahl der Treffer: 143
Erstellt: Thu, 28 Mar 2024 23:06:37 +0100 in 0.0437 sec


Feldhusen, Kai; Deiterding, Ralf; Wagner, Claus
A dynamically adaptive lattice Boltzmann method for thermal convection problems. - In: International journal of applied mathematics and computer science, ISSN 2083-8492, Bd. 26 (2016), 4, S. 735-747

https://doi.org/10.1515/amcs-2016-0051
Feldmann, Daniel; Wagner, Claus
On the influence of computational domain length on turbulence in oscillatory pipe flow. - In: International journal of heat and fluid flow, ISSN 1879-2278, Bd. 57 (2016) Part A (Okt.), Seite 229-244

http://dx.doi.org/10.1016/j.ijheatfluidflow.2016.09.005
du Puits, Ronald; Willert, Christian E.
Boundary layers in turbulent Rayleigh-Bénard convection. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), DY 57.3, insges. 1 S.

Kaiser, Robert; du Puits, Ronald
Global flow modes in turbulent Rayleigh-Bénard convection. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), DY 57.13, insges. 1 S.

Schuster, Roland; Ehrenfried, Klaus; Henning, Arne; Wagner, Claus
Validation of a geometric diffraction model with respect to level-time history prediction. - In: Fortschritte der Akustik, ISBN 978-3-939296-10-2, (2016), S. 868-871

Du Puits, Ronald; Willert, Christian
The evolution of the boundary layer in turbulent Rayleigh-Bénard convection in air. - In: Physics of fluids, ISSN 1089-7666, Bd. 28 (2016), 4, 044108, insges. 15 S.

We report measurements of the near-wall flow field in turbulent Rayleigh-Bénard convection in air (Pr = 0.7) using particle imagevelocimetry. The measurements were performed in a thin, rectangular sample at fixed Rayleigh number Ra = 1.45 × 10^10. In particular, we focus on the evolution of the boundary layer that a single convection roll generates along its path at the lower horizontal plate. We identify three specific flow regions along this path: (i) a region of wall-normal impingement of the down flow close to one corner of the sample, (ii) a region where a shear layer with almost constant thickness evolves, and (iii) a region in which this boundary layer grows and eventually detaches from the plate surface at the opposite corner of the sample. Our measurements with a spatial resolution better than 1/500 of the total thickness of the boundary layer show that the typical velocity field as well as its statistics qualitatively varies between the three flow regions. In particular, it could be verified that the shear layer region covering about 75% of the total area of the plate is in transition to turbulence at the Rayleigh number as low as investigated in the present work.



https://doi.org/10.1063/1.4947261
Konstantinov, Mikhail; Wagner, Claus
Numerical simulation of the thermal comfort in a model of a passenger car cabin. - In: New results in numerical and experimental fluid mechanics X, (2016), S. 383-393

Dillmann, Andreas; Heller, Gerd; Krämer, Ewald; Wagner, Claus; Breitsamter, Christian
New results in numerical and experimental fluid mechanics X : contributions to the 19th STAB/DGLR Symposium Munich, Germany, 2014. - [Cham] : Springer, 2016. - xvi, 897 Seiten. - (Notes on numerical fluid mechanics and multidisciplinary design ; Volume 132) ISBN 978-3-319-27278-8
19th DGLR/STAB-Symposium held in Munich, Germany, 4-5 November 2014. - Mit Literaturangaben und Index

"This book presents contributions to the 19th biannual symposium of the German Aerospace Aerodynamics Association (STAB) and the German Society for Aeronautics and Astronautics (DGLR). The individual chapters reflect ongoing research conducted by the STAB members in the field of numerical and experimental fluid mechanics and aerodynamics, mainly for (but not limited to) aerospace applications, and cover both nationally and EC-funded projects. Special emphasis is given to collaborative research projects conducted by German scientists and engineers from universities, research-establishments and industries. By addressing a number of cutting-edge applications, together with the relevant physical and mathematics fundamentals, the book provides readers with a comprehensive overview of the current research work in the field. Though the book's primary emphasis is on the aerospace context, it also addresses further important applications, e.g. in ground transportation and energy."--



Czarnota, Tomasz; Wagner, Claus
Turbulent convection and thermal radiation in a cuboidal Rayleigh-Bénard cell with conductive plates. - In: International journal of heat and fluid flow, ISSN 1879-2278, Bd. 57 (2016), S. 150-172

The interactions between turbulent convection and surface-to-surface radiation are investigated by means of direct numerical simulations (DNS) performed for a cuboidal Rayleigh-Bénard cell bounded by horizontal plates of finite thickness and with high and low conductivities. The simulations are conducted for the Prandtl number Pr = 0.7, Rayleigh numbers ranging from Ra = 3.5 × 105 to Ra = 6.3 × 107, radiation numbers between Nr = 0.0008 and Nr = 0.0026, and temperature ratios between = 29 and = 45. Additionally, blackbody radiation is considered, and the side walls are assumed to be transparent to radiation but adiabatic for conduction. The DNS are performed with a well validated fourth order accurate finite volume method. Analysing the DNS data it is shown that radiation renders the bulk more uniform by enlarging the large scale circulations and damps turbulence intensities by decreasing the buoyancy force. Howthese effects depend on Ra and the plates' diffusivity is also discussed. The temperatures of the cold plumes are affected equally by radiation, while those of the hot plumes are affected differently, depending on their location. Radiation affects the temperature of the heat sources by cooling the heating plates and heating the cooling plates. The spatial fluctuations at the interfaces are decreased or increased by radiation, depending on the plates' diffusivity. The temporal fluctuations are not affected by radiation when high conductivity plates are employed. The radiative heat flux contributes considerably to the total one, particularly for low conductivity plates and low Ra. Heat radiation also initiates a so-called convective drop. It is found that in regions where the plumes emerge, only the radiative heat flux and its intensity are responsible for this drop, while in regions where the plumes arrive, the convective heat transported by the arriving plumes contributes as well. Small variations in the temperature distribution at the interfaces do not affect irradiation, which implies the possibility of further simplifications and a decrease in the computational cost. The convective and radiative heat fluxes are anticorrelated for low conductivity plates and uncorrelated in space for high conductivity plates. Furthermore, it is shown that the radiative heat transfer increases with the control parameters for radiation, yet the increase is more sensitive to variations of the radiation number than the temperature ratio. On the other hand, the convective heat transfer and the effective temperature difference decrease whenever any of the control parameters for radiation increase. The meaning of the control parameters for radiation is discussed and the dependencies are expressed with scaling functions.



http://dx.doi.org/10.1016/j.ijheatfluidflow.2015.10.006
Liot, Olivier; Salort, Julien; Kaiser, Robert; du Puits, Ronald; Chillà, Francesca
Boundary layer structure in a rough Rayleigh-Bénard cell filled with air. - In: Journal of fluid mechanics, ISSN 1469-7645, Bd. 786 (2016), S. 275-293

In this experimental work, the aim is to understand how turbulent thermal flows are enhanced by the estabilization of the boundary layers. Square-stud roughness elements have been added on the bottom plate of a rectangular Rayleigh-Bénard cell in air, to trigger instabilities in the boundary layers. The top plate is kept smooth. The cell proportions are identical to those of the water cell previously operated and described by Salort et al. (Phys. Fluids, vol. 26, 2014, 015112), but six times larger. The very large size of the Barrel of Ilmenau allows detailed velocity fields to be obtained using particle image velocimetry very close to the roughness elements. We found that the flow is quite different at low Rayleigh numbers, where there is no heat-transfer enhancement, and at high Rayleigh numbers where there is a heat-transfer enhancement due to the roughness. Below the transition, the fluid inside the notch, i.e. between the studs, is essentially at rest, though it is slowly recirculating. The velocity profiles on the top of obstacles and in grooves are fairly compatible with those obtained in the smooth case. Above the transition, on the other hand, we observe large incursions of the bulk inside the notch, and the velocity profiles on the top of obstacles are closer to the logarithmic profiles expected in the case of turbulent boundary layers.



http://dx.doi.org/10.1017/jfm.2015.649