Numerical investigation of the unsteady behavior of supersonic plane wakes

The flow in the wake region of a two-dimensional body has been studied using direct numerical simulations. The nature of instabilities in the wake and its bounding shear layers is addressed for a Mach number of M = 2.46, and the structures that arise from these instabilities are observed. A code was developed to solve the compressible Navier- Stokes equations in two or three dimensions. A spatial model is used, with the computational domain arranged around the trailing edge of a two-dimensional flat plate with a blunt base. Starting at Reynolds numbers of about Re = 30,000, the flow becomes two-dimensionally unstable with respect to sinuous disturbances, resulting in the periodic formation of vorticity structures. Starting at about Re = 100,000, an intermittent shear layer instability was also found, excited by sinuous disturbances. The two instability modes interact to produce a “chaotic” behavior. Above Re = 200,000, the shear layer instability appears without the presence of the sinuous disturbances, forming rows of vortices in the shear layers. Preliminary three-dimensional simulations were carried out, examining the variation in the growth rate of three-dimensional disturbances with spanwise wavelength.