Large Eddy Simulations using an unstructured grid compressible Navier-Stokes algorithm

Large Eddy Simulation (LES) of the decay of isotropic turbulence and of cha nnel flow has been performed using an explicit second-order unstructured gr id algorithm for tetrahedral cells. The algorithm solves for cell-averaged values using the finite volume form of the unsteady compressible filtered N avier-Stokes equations, The inviscid fluxes are obtained from Godunov's exa ct Riemann solver, Reconstruction of the flow variables to the left and rig ht sides of each face is performed using least squares or Frink's method. T he viscous fluxes and heat transfer are obtained by application of Gauss' t heorem. LES of the decay of nearly incompressible isotropic turbulence has been performed using two models for the SGS stresses: the Monotone Integrat ed Large Eddy Simulation (MILES) approach, wherein the inherent numerical d issipation models the sub-grid scale (SGS) dissipation, and the Smagorinsky SGS model. The results using the MILES approach with least squares reconst ruction show good agreement with incompressible experimental data. The cont ribution of the Smagorinsky SGS model is negligible. LES of turbulent chann el flow was performed at a Reynolds number (based on channel height and bul k velocity) of 5600 and Mach number of 0.5 (at which compressibility effect s are minimal) using Smagorinsky's SGS model with van Driest damping. The r esults show good agreement with experimental data and direct numerical simu lations for incompressible channel flow. The SOS eddy viscosity is less tha n 10% of the molecular viscosity, and therefore the LES is effectively MILE S with molecular viscosity.