Most flows of engineering interest are turbulent and turbulence has a significantimpact on the performance of engineering systems. The drag on a body is generallymuch greater if the boundary layer is turbulent.
Turbulence also increasesheat transfer between a fluid and a surface.
In addition, turbulent mixingis important to combustion. With LES the motion ofthe largest eddies are solved for directly while the effects of the unresolvedsmall scale eddies are modeled. In contrast, with DNS all the relevant lengthscales within the turbulence are resolved and no modeling is needed. The results of the simulations are used to increase our understanding of turbulence andto test and improve turbulence models. Parallel computing and advanced numerical methods is another area of interest.