Please use this identifier to cite or link to this item: https://doi.org/10.21256/zhaw-4911
Title: A gas-kinetic scheme for turbulent flow
Authors : Righi, Marcello
Published in : Flow, turbulence and combustion
Volume(Issue) : 97
Issue : 1
Pages : 121
Pages to: 139
Publisher / Ed. Institution : Springer
Issue Date: Jul-2016
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (publication)
Language : English
Subject (DDC) : 530: Physics
Abstract: RANS simulations may not provide accurate results for all flow conditions. The interaction between a shock wave and a turbulent boundary layer is an example which may still be difficult to simulate accurately. Beside the inability to reproduce physical phenomena such as shock unsteadiness, the argument is put forward that the conventional numerical schemes, based on the Navier-Stokes equations, may be unable to generate a physically consistent turbulent stress tensor in the presence of large unresolved scales of motion. A large ratio between unresolved and resolved scales of motion, a sort of Knudsen number based on turbulent fluctuations, might introduce inaccuracies for which the turbulence model is not accountable. In order to improve the accuracy of RANS simulations, researchers have suggested various ad-hoc modifications to standard turbulence models which limit eddy viscosity or the turbulent stress tensor in the presence of strong gradients. Gas-kinetic schemes might be able to improve RANS predictions in shocklayers by removing or limiting the errors caused by the large scales ratio. These schemes are a class of their own; in the framework of a finite-volume or finite-elements discretizations, they model the numerical fluxes on the basis of the Boltzmann equation instead of the Navier-Stokes equations as is conventionally done. In practical terms, these schemes provide a higher accuracy and, more importantly, an in-built “multiscalar” mechanism, i.e. the ability to adjust to the size of unresolved scales of motion. This property makes them suitable for shock-capturing and rarefied flow. Gas-kinetic scheme may be coupled to a conventional RANS turbulence model; it is shown that the turbulent stress tensor is naturally adjusted as a function of the unresolved-to-resolved scales ratios and achieves a higher physical consistency than conventional schemes. The simulations shown - well-known benchmark cases with strong shock-boundary layer interactions - have been obtained with a standard two-equation turbulence model (k- ω). It is shown that the gas-kinetic scheme provides good quality predictions, where conventional schemes with the same turbulence model are known to fail.
Further description : Published Online: 26 November 2015, erworben im Rahmen der Schweizer Nationallizenzen (www.nationallizenzen.ch)
Departement: School of Engineering
Organisational Unit: Institute of Mechanical Systems (IMES)
Publication type: Article in scientific journal
DOI : 10.21256/zhaw-4911
10.1007/s10494-015-9677-2
ISSN: 1386-6184
1573-1987
URI: https://digitalcollection.zhaw.ch/handle/11475/13403
Restricted until : 2020-07-01
Appears in Collections:Publikationen School of Engineering

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