PIV Study and Numerical Simulation of the Unsteady Flowfield of Overexpanded Supersonic Impinging Jet at Ma=3

Abstract

Results of a Particle Image Velocimetry (PIV) experimental study and unsteady simulation about an overexpanded axisymmetric supersonic impinging jet at Ma=2.982 and dimensionless impinging height as Z/D=4 were presented in this paper. Especially, the detailed unsteady phenomena of the global flowfield coherent structures were focused both by PIV experimentally and numerically. The PIV results clearly demonstrated the formation of the shock cell, the stagnation bubble. With the help of the unsteady CFD technique, the unsteady process of the generation of the oblique shock wave and the Mach disk, the propagation of the oblique shock wave and its reflection on the jet shearing layer and the induced expansion wave, then the formation of the shock cell, the presentation of the stagnation bubble, the appearance of the entrainment vortex and its propagation radically towards the outside, were all further clearly revealed. Both the PIV measurements and the CFD results showed the highly unsteady, oscillatory behavior of the impinging jet. All these results are helpful to understand the overexpanded axisymmetric supersonic jet impingement phenomenon.