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Hybrid LES/RANS Methods for Compressible Turbulent Boundary Layer

난류경계층 유동해석을 효율적으로 모사하기 위해, Reynolds-averaged Navier-Stokes Simulation기법과 Large Eddy Simulation기법의 혼합형태의 새로운 수치모형을 개발하고자 한다

A new hybrid large-eddy simulation / Reynolds-averaged Navier-Stokes simulation (LES/RANS) method is presented in this work. In this approach, the resolved turbulence kinetic energy, ensemble-averaged modeled turbulence kinetic energy and turbulence frequency, and time-resolved turbulence frequency are used to form an estimate of an outer-layer turbulence length scale that is nearly Reynolds-number independent. The ratio of this outer-layer scale with an inner-layer length scale (proportional to the wall distance) is used to construct a blending function that facilitates the shift between an unsteady RANS formulation near solid surfaces and a LES formulation away from the wall. The new model is tested through simulations of compressible flat-plate boundary layers over a wide range of Reynolds numbers and Mach 2.85 flow over a smooth compression ramp. The results show that the new model provides results for mean and second-moment statistics that are in good agreement with experiment and are comparable to those obtained using an earlier model which required a case-by-case calibration of a model constant.

Edwards et al. (2008) AIAA Journal; Choi et al. (2008) AIAA Journal; Gieseking et al. (2010) AIAA Journal

Mean velocity profies for the present hybrid LES/RANS simulation

The effect of Reynolds number on skin-friction coefficient

Vortical structures visualized using an iso-surface of swirl strength

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