A new wall model for large Eddy simulation of separated flows
| Autor: | Ahmad Fakhari |
|---|---|
| Přispěvatelé: | Universidade do Minho |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
Von Kármán constant separated flow 01 natural sciences Law of the wall 010305 fluids & plasmas Physics::Fluid Dynamics Flow separation 0103 physical sciences Shear stress Shear velocity 0105 earth and related environmental sciences Fluid Flow and Transfer Processes Physics Science & Technology Turbulence Mechanical Engineering immersed boundary Mechanics wall layer model Condensed Matter Physics body fitted Adverse pressure gradient LES Large eddy simulation |
| Zdroj: | Fluids Volume 4 Issue 4 Repositório Científico de Acesso Aberto de Portugal Repositório Científico de Acesso Aberto de Portugal (RCAAP) instacron:RCAAP |
| Popis: | The aim of this work is to propose a new wall model for separated flows which is combined with large eddy simulation (LES) of the flow field in the whole domain. The model is designed to give reasonably good results for engineering applications where the grid resolution is generally coarse. Since in practical applications a geometry can share body fitted and immersed boundaries, two different methodologies are introduced, one for body fitted grids, and one designed for immersed boundaries. The starting point of the models is the well known equilibrium stress model. The model for body fitted grid uses the dynamic evaluation of the von Ká rmá n constant &kappa of Cabot and Moin (Flow, Turbulence and Combustion, 2000, 63, pp. 269&ndash 291) in a new fashion to modify the computation of shear velocity which is needed for evaluation of the wall shear stress and the near-wall velocity gradients based on the law of the wall to obtain strain rate tensors. The wall layer model for immersed boundaries is an extension of the work of Roman et al. (Physics of Fluids, 2009, 21, p. 101701) and uses a criteria based on the sign of the pressure gradient, instead of one based on the friction velocity at the projection point, to construct the velocity under an adverse pressure gradient and where the near-wall computational node is in the log region, in order to capture flow separation. The performance of the models is tested over two well-studied geometries, the isolated two-dimensional hill and the periodic two-dimensional hill, respectively. Sensitivity analysis of the models is also performed. Overall, the models are able to predict the first and second order statistics in a reasonable way, including the position and extension of the downward separation region. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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