Hybrid Simulation Approach for Cavity Flows: Blending, Algorithm, and Boundary Treatment Issues

TLDR

Advances in high‑performance computing and numerical algorithms have spurred the creation of hybrid turbulence models that merge the robustness of Reynolds‑averaged Navier–Stokes equations with the detailed physics of large‑eddy simulation. The study proposes straightforward modifications to standard second‑order accurate RANS solvers to improve their ability to resolve large‑eddy motions. The authors introduce a blending function that uses local turbulence characteristics and mesh spacing to switch between RANS and LES equations, enabling flexible closure model combinations and simplifying grid generation.

Abstract

The maturation of high-performance computer architectures and computational algorithms has prompted the development of a new generation of models that attempt to combine the robustness and efficiency offered by the Reynolds averaged Navier-Stokes equations with the higher level of modeling offered by the equations developed for large eddy simulation. The application of a new hybrid approach is discussed, where the transition between these equation sets is controlled by a blending function that depends on local turbulent flow properties, as well as the local mesh spacing. The utilization of local turbulence properties provides added control in specifying the regions of the flow intended for each equation set, removing much of the burden from the grid-generation process. Moreover, the model framework allows for the combination of existing closure model equations, avoiding the difficulty of formulating a single set of closure coefficients that perform well in both Reynolds averaged and large eddy simulation modes. Simple modifications to common second-order accurate Reynolds averaged Navier-Stokes algorithms are proposed to enhance the capturing of large eddy motions