Large Eddy Simulation in Complex Geometric Configurations Using Boundary Body Forces

Abstract

Anumericalmethodispresentedthatallowslargeeddysimulation (LES)ofturbulente owsincomplexgeometric cone gurations with moving boundaries and that retains the advantages of solving the Navier ‐Stokes equations on e xed orthogonal grids. The boundary conditions are applied independently of the grid by assigning body forces over surfaces that need not coincide with coordinate lines. The use of orthogonal, nondeforming grids simplie es grid generation, facilitates theimplementation of high-order,nondissipativediscretization schemes, andminimizes the spatial and temporal variations in e lter width that complicate unstructured deforming-grid LES. Dynamic subgrid-scaleturbulence models areparticularly appealing in combination with the body-forceprocedure because the dynamic model accounts automatically for the presence of solid walls without requiring damping functions. The method is validated by simulations of the turbulent e ow in a motored axisymmetric piston ‐cylinder assembly for which detailed experimental measurements are available. Computed mean and rms velocity proe les show very good agreement with measured ensemble averages. Thepresent numerical code runs on small, personal computerlike workstations. For a comparable level of accuracy, computational requirements (memory and CPU time ) are at least a factor of 10 lower compared to published simulations for the same cone guration obtained using an unstructured, boundary-e tted deforming-grid approach.