A Rapid and Accurate Switch from RANS to LES in Boundary Layers Using an Overlap Region
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An efficient recycling algorithm is developed for injecting resolved turbulent content in a boundary layer as it switches from a Reynolds Averaged Navier-Stokes (RANS) type treatment to a Large Eddy Simulation (LES) type treatment inside a generalized Detached-Eddy Simulation (DES). The motivation is to use RANS in the thinnest boundary-layer area, following the original argument in favour of DES, and LES in the thicker boundary-layer areas especially approaching separation, to improve accuracy and possibly obtain unsteady outputs. The algorithm relies on an overlap of the RANS and LES domains and, therefore, the availability of both RANS and LES solutions in the recycling region, which is about 5 boundary-layer thicknesses long. This permits a smooth transfer of the turbulent stresses from this section to the LES inflow. The continuity of the skin-friction distribution is very good, reflecting the excellent viability of the resolved turbulence. The approach is validated in a flat-plate boundary layer and an airfoil near stall, with mild pressure gradient near the interface, and then applied to the compressible flow over an idealized airliner windshield wiper. The pressure fluctuations at reattachment are 12dB more intense than under a simple boundary layer at the same speed, and the output contains all the quantities needed to calculate the transmission of sound through the glass.
KeywordsRANS-LES coupling IDDES Inflow turbulent content Recycling
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- 1.Spalart, P.R., Jou, W.-H., Strelets, M., Allmaras, S.R.: Comments on the feasibility of LES for wings, and on a hybrid RANS/LES approach. In: Liu, C., Liu, Z. (eds.) Advances in DNS/LES, pp. 137–147. Greyden, Columbus (1997)Google Scholar
- 5.Leschziner, M.A., Li, N., Tessicini, F.: Computational methods combining eddy simulation with approximate wall-layer models for predicting separated turbulent flows. ERCOFTAC Bulletin. 72 (2007)Google Scholar
- 8.Batten, P., Goldberg, U., Chakravarthy, S.: LNS—an approach towards embedded LES, AIAA Paper 2002-0427 (2002)Google Scholar
- 12.Mathey, F., Cokljat, D., Bertoglio, J.P., Sergent, E.: Specification of inlet boundary condition using vortex method. In: Hanjalic, K., Nagano, Y., Tummers, M. (eds.) Turbulence, Heat and Mass Transfer 4. Begell House Inc. (2003)Google Scholar
- 15.Spalart, P.R., Allmaras, S.R.: A one-equation turbulence model for aerodynamic flows. La Rech. Aerospatiale. 1, 5–21 (1994)Google Scholar
- 19.LESFOIL: Large-Eddy Simulation of Flow around a High Lift Airfoil. Davidson, L., Cokljat, D., Fröhlich, J., Lescziner, M.A., Mellen, C., Rodi, W. (eds.) Notes on Numerical Fluid Mechanics and Multidisciplinary Design. 83. Springer, Berlin (2003)Google Scholar
- 20.Nolin, G., Mary, I.: Test Case 06: A-airfoil. http://cfd.mace.manchester.ac.uk/desider/private/meeting-docs/file_meet-115287900506_ONERA.tar (2007). Accessed 28 August 2010
- 21.Strelets, M.: Detached Eddy Simulation of massively separated flows. AIAA Paper 2001-0879 (2001)Google Scholar
- 22.Rogers, S.E., Kwak, D.: An upwind differencing scheme for the time-accurate incompressible Navier-Stokes equations. AIAA Paper 1988-2583-CP (1988)Google Scholar