Numerical Simulation of Supersonic Free Shear Layers.

摘要

3-D supersonic shear layers can asymptotically approach a growth rate equal to 30% of that of subsonic shear layers. In an attempt to explain this phenomena, a series of analytical, experimental and computational studies have recently been carried out. Many of these studies focused on 2-D supersonic shear layers. In these studies, and in particular, studies based on stability analysis fo 2-D supersonic shear layers, it was found that the shear layer growth rate approaches zero (and not the 30% observed originally) as the connective Mach number of the shear layer increased from subsonic and supersonic. Several theories have been proposed to explain the discrepancies between 2-D analysis and 3-D observations. The objective of this research is to study the stability and growth characteristics of 3-D free shear layers through a numerical solution of the 3-D unsteady, compressible Navier-Stokes equations. A general solution procedure has been constructed that may be used to study the temporal and spatial growth of 2-D and 3-D waves, to study the effects of random initial disturbances on the shear layer growth and to study the effects of wall on the shear layer growth. This procedure thus complements the well developed techniques of linear stability analysis, and allows one to study additional non-linear phenomena such as saturation of modes, vortex pairing phenomena etc. (JHD)