Experimental study on the evolution of heavy gas cylinder under reshock condition by PIV method

Evolution of a membrane-less heavy (SF6 )gas cylinder under reshock condition is experimentally investigated in a horizontal shock tube with particle image velocimetry (PIV ) method.As a fundamental interface configuration,gas cylinder evolution impinged by a single shock wave is extensively investigated while the related research under reshock condition is sel-dom performed.Illuminated by a continuous laser sheet,the interface morphology after the inci-dent shock and reshock impact is characterized by glycol droplets and captured by a high-speed camera.The generation and development of counter-rotating vortex pair after incident shock im-pact is observed and secondary vortex rings,which have opposite rotating directions with the o-riginal vortex rings,are generated after the reshock passage because of the opposite pressure gra-dient induced by reshock compared with the incident shock.Because the velocity of the flow field after reshock is very small,the PIV measurement based on the Matpiv procedure is employed to capture the flow field after reshock.The continuous velocity and vorticity fields are obtained with the help of the continuous light source and high speed camera.Compared with the PIV algorithm based on the double-exposure technique,continuous velocity field can be obtained in a single test run based on the high-speed technique in this experiment.The circulation derived from PIV measurements is compared with the existed analytical model and a good agreement is achieved, which validates the feasibility of the experimental method.