Unsteady simulation of jets in a cross flow

Effects of the computational time step and grid stretching on numerical solutions of a two-dimensional laminar boundary layer with a planar jet injected from a wall are investigated using a fully implicit time advancement scheme. A very large CFL number (CFL = 64) is determined for a time accurate solution, which provides a factor of 50 savings in the required CPU time as compared to a semi-implicit method, It is also noted that the grid stretching generates 2 - Delta waves in the flow investigated. A full three-dimensional numerical simulation has been performed to qualitatively investigate the interaction of jets in a turbulent cross flow using the direct numerical simulation technique. Turbulent vortex sheddings are observed behind jets and show a rapid diffusion in the downstream. It is also shown that a counter-rotating vortex pair existing in the downstream of the jet contributes an important role in the dynamics of the jet in a cross flow. (C) 1997 Academic Press.