Experimental investigation on the interaction of planar shock wave with cylindrical gaseous inhomogeneity

Abstract

The interaction of a planar shock wave (Mach number of 1.2) with a gas cylinder (helium cylinder or SF6 cylinder) is experimentally studied using the high-speed schlieren photography. Because the soap film has less influence on the interface evolution than the solid diaphragm and the soap film cylinder can effectively suppress the gas exchange at the interface compared with the diaphragm-less cylinder, a circular wire-restriction method of using the soap film technique is introduced to generate the interface separating the experimental gas from the ambient gas. Illuminated by a DC source, the evolution of the gas cylinder accelerated by a shock wave is captured by the high-speed video camera in a single test run and the wave patterns are also observed. It is shown from the results that the SF6 cylinder is firstly compressed and accelerated by the shock, and then a jet is formed at the downstream interface due to the transmitted shock focusing. Subsequently, induced by the vorticity, the cylinder is developed into a mushroom shape and finally the turbulent mixing occurs. After the impact of the shock wave, the helium cylinder is firstly accelerated and the reversal phase occurs at the upstream interface. Afterwards, a jet is generated from the upstream interface and gradually tears through the downstream interface. Eventually, the interface is developed into two independent vortexes. Compared with the previous studies, the results in this work behave more symmetry and fewer disturbances are generated in the flow field due to the absence of the holder. Moreover, the variation of the interface scales with time is measured from which the changes of the interface can be well interpreted. At last, the shock and interface velocities in SF6 case obtained in the experiment are found to have a satisfactory agreement with the theoretical prediction from one-dimensional gas dynamics, which verifies the interface formation method to some extent.