Experimental investigation of reshocked spherical gas interfaces

• Published in: Physics of fluids (1994) 2012-05, Vol.24 (5), p.054101-054101-17
• Main Authors: Si, Ting, Zhai, Zhigang, Yang, Jiming, Luo, Xisheng
• Format: Article
• Language: English
• Subjects: Compressible flows; shock and detonation phenomena; Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); Hydrodynamic stability; Instrumentation for fluid dynamics; Interfacial instability; Physics; Shock-wave interactions and shock effects
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.4711866

The evolution of a spherical gas interface under reshock conditions is experimentally studied using the high-speed schlieren photography with high time resolutions. A number of experimental sets of helium or SF 6 bubble surrounded by air for seven different end wall distances have been performed. Distinct flow structures are observed due to the additional vorticity and wave configuration caused by the reshock. In the air/helium case, the deformation of the reshocked bubble is dependent on the development of the penetrating air jet along the symmetry axis of the bubble. In general, two separate vortex rings can be observed, i.e., one develops slowly, and the other approaches and eventually impinges on the shock tube end wall. In the air/SF 6 case, two SF 6 jets moving in opposite directions are generated and the oscillation of the interface is observed for small end wall distances, while small scale vortex morphologies on the gas interface are found for large end wall distances. The physical mechanisms of the baroclinic vorticity generation and the pressure perturbation are highlighted in the interface evolution process. Based on the sequence of the schlieren images obtained during a single run for each case, the x - t diagrams of the shock and reshock interacting with the helium or SF 6 bubble are plotted and the velocities estimated in linear stages are compared with those calculated from one-dimensional gas dynamics. The changes with time in the characteristic bubble sizes including the interface length, height, and vortex diameter are also measured.