Direct and large-eddy simulations of turbulence in fluids

Abstract

As a result of the increasing power of supercomputers numerical simulation of turbulent flows has become feasible. In the present paper we give a short review of the requirements for such simulations. First we discuss so-called direct numerical simulation (DNS), where the equations of motion for a turbulent flow are solved in all detail. This application is illustrated with two examples, viz. the transition from laminar to turbulence in a differential heated cavity and a fully developed turbulent pipe flow. The second application of turbulence simulation is large-eddy modelling where only the large scales of turbulence are numerically resolved and the small scales are parameterized by a turbulence model. As example for this case we discuss the atmospheric boundary layer and in particular the dispersion of pollutants by atmospheric turbulence. We close our contribution with a discussion of the computer requirements necessary for turbulence simulation together with an outlook in the future in which we consider the pro's and contra's of massively parallel systems.