The Reynolds number of the simpler turbulent flows are currently approaching those of the smaller-scale experiments. DNS of forced isotropic turbulence has been conducted on 5123 grids by several workers with the help of parallel computers. The Reynolds number in these computations actually exceeds that in most laboratory experiments. DNS is most important in problems where simplification to the governing unsteady, nonlinear equations have not as yet been adequately validated.
Databases generated by DNS [13] provide results on turbulent flow statistics which are in good agreement with experiments thus greatly increasing the confidence in the technology.
These databases also offer the opportunity to extract information from the flow field which cannot, or only with much difficulty, be obtained from experiments. The availability of DNS data has resulted in novel approaches to model evaluation and allows testing of the concepts behind a model. DNS data is extensively used to evaluate LES results which are an order of magnitude faster to obtain. The availability of this detailed flow information has certainly improved our understanding of physical processes in turbulent flows which thus emphasizes the importance of DNS in present scientific research. Due to the very good correlation between the DNS results and the experimental data, DNS has become synonymous with the term ``Numerical Experiment''.