Separation of reflected shock waves due to the secondary interaction with vortices: Another mechanism of sound generation

The development of a flow field and the generation of sound due to the interaction between a shock wave and two vortices are simulated numerically. The two vortices are initially set either in tandem or parallel to the incident shock wave. The two-dimensional, unsteady, compressible Navier-Stokes equations are solved by a finite difference method. The results show that reflected shock waves, which are generated by the interaction between the incident shock wave and a vortex, interact with the other vortex and produce new acoustic waves, in addition to the waves observed in a single vortex case. For sufficiently strong vortices, the waves thus produced interact with the vortices again and produce further acoustic waves. The results suggest that separation of reflected shock waveṡ due to the secondary interaction with vortices may be one of the key mechanisms in the generation of acoustic waves in supersonic turbulent flows.