Subgrid-Scale modeling

Abstract

The purpose of this lecture is to give an overview of the subgrid scale models used for Large Eddy Simulations (LES).The first models where essentially eddy-viscosity models,where the turbulent viscosity coefficient was found by simple dimensional considerations (the mixing length theory) ortaking into account Kolmogorov theory (theSmagorinsky model).Since then there have been many improvements, and now some of the physical ingredients of turbulence, such as the localbackscatter and the anisotropy of small scale structures, canbe successfully taken into account.Far from being a black boxtool to obtain answers toturbulent flow problems, the Large Eddy Simulation techniqueis still a work in progress with many odds and ends. We give in this lecture an overview of the historicaldevelopment of turbulence models and wepoint out the lights and shadows of them with attention to the open problems that still remain to be solved.