NUMERICAL SIMULATION ON A PLANAR SUPERSONIC FREE SHEAR LAYER WITH MIXING ENHANCEMENT

摘要

In the present study, direct numerical simulations have been carried out on a planar supersonic free shear flow at Mc=0.5. Navier-Stokes equations were solved with a finite difference method of third-order accuracy. At the first, the validation of computational grids was made, and the computational accuracy was investigated on different grid sizes by the linear mode of a 2-D parallel mixing layer. Then the DNS method was used to 3-D DNS computations with validated grid size. In the DNS study on a 3-D planar free shear layer with 2-D disturbing wave, it was found that a very week lateral wave was modulated naturally. By adding this 3-D wave at sub-harmonic frequency to the disturbing source of the primary wave, the instability process was enhanced greatly. It is noticeable that λ-structure of vortex developed, and the mixing enhancement can be achieved in this way. It is an important fact that distinguishable difference exists in supersonic shear layer between 2-D and 3-D considerations.