Towards an enhanced protection of attached boundary layers in hybrid RANS/LES methods
Autor: | Nicolas Renard, Sébastien Deck |
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Přispěvatelé: | DAAA, ONERA, Université Paris Saclay (COmUE) [Meudon], ONERA-Université Paris-Saclay |
Rok vydání: | 2020 |
Předmět: |
HYBRID RANS/LES METHODS
Materials science Physics and Astronomy (miscellaneous) 02 engineering and technology GREY AREA MITIGATION 01 natural sciences RANS/LES HYBRIDE [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] 010305 fluids & plasmas law.invention Supercritical airfoil Flow separation GRID INDUCED SEPARATION 0203 mechanical engineering law 0103 physical sciences BOUNDARY LAYER SHIELDING MODELLED STRESS DEPLETION ZDES Numerical Analysis Turbulence Applied Mathematics Turbulence modeling Mechanics ZONAL DETACHED EDDY SIMULATION Computer Science Applications Computational Mathematics Boundary layer 020303 mechanical engineering & transports Modeling and Simulation Electromagnetic shielding Reynolds-averaged Navier–Stokes equations Transonic COUCHE LIMITE |
Zdroj: | Journal of Computational Physics Journal of Computational Physics, Elsevier, 2020, 400, pp.108970. ⟨10.1016/j.jcp.2019.108970⟩ |
ISSN: | 0021-9991 1090-2716 |
DOI: | 10.1016/j.jcp.2019.108970 |
Popis: | International audience; A robust strategy for the RANS shielding of attached boundary layers in a hybrid RANS/LES context is presented, addressing two major issues. Firstly, the attached boundary layers must be detected to ensure their RANS treatment, but the original shielding function used by automatic methods such as DDES (2006) or ZDES mode 2 (2012) fails for fine meshes and/or with adverse pressure gradients, motivating the present study. Secondly, even with a stronger shielding, there should not be an excessive delay in the formation of instabilities and resolved LES content in free shear layers. Both objectives cannot be simultaneously reached by only tuning a constant in the original shielding function. The proposed new ZDES mode 2 consequently involves three main ingredients, namely a second shielding function detecting the outer part of the wake layer including with strong adverse pressure gradients, an inhibition function which switches off the second shielding when flow separation is detected, and a significant enhancement of the destruction of eddy viscosity in grey areas. The calibration of the method relies on a set of boundary layers at various Reynolds numbers and pressure gradients conditions and is confirmed by a priori tests in three-dimensional flows around curved geometries. The resulting case-independent model, the new ZDES mode 2, is assessed on four test cases, namely a flat-plate boundary layer, a mixing layer, a backward facing step and transonic buffet over a supercritical airfoil. Overall, it is shown that the new ZDES mode 2 is relevant with respect to four objectives: protection of attached boundary layers for any grid cell size (including infinite mesh refinement) and pressure gradient, RANS shielding at least as broad as the original shielding in any situation, minimum delay in the formation of resolved LES content, and full compatibility of the resulting subgrid scale model in the LES branch with the other modes of ZDES (modes 1 and 3) ensuring a continuous treatment of resolved turbulence across zones treated with different ZDES modes. The new robust ZDES mode 2 consequently is a case-independent answer to the demand for a general automatic and robust RANS/LES treatment of attached and massively separated flows. |
Databáze: | OpenAIRE |
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