Self-similarity and mixing characteristics of turbulent mixing layers starting from laminar initial conditions

Direct numerical simulations of two turbulent mixing layers starting from low- and high-gradient laminar profiles have been performed, to assess the transitional and long time characteristics of these flows. The simulations include a passive scalar with Schmidt number of 0.7, and were conducted using a grid resolution of 512 x 256 x 257 implemented in parallel on 128 nodes of the Intel Paragon supercomputer. The two mixing layers at their final turbulent condition achieved Reynolds number of approximate to 11 000. It is found that although the self-similarity appears to have been achieved early in the evolution of these flows, long time development is necessary for the mixing characteristics and the statistical content of these flows to become similar to the mixing layers that start from turbulent boundary layers.