The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and transport.The numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very well.Simulations are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) interface.Five different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of triangle.The results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock waves.The generation and the distribution of vorticity on the interfaces with five different shapes also have dissimilarities.The circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical model.Some characteristic scales of the interface are tracked.Under the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.
FAN MeiRuZHAI ZhiGangSI TingLUO XiShengZOU LiYongTAN DuoWang
The influences of the acoustic impedance and shock strength on the jet formation in shock-heavy gas bubble interaction are numerically studied in this work. The process of a shock interacting with a krypton or a SF6 bubble is studied by the numerical method VAS2D. As a validation, the experiments of a SF6 bubble accelerated by a planar shock were performed. The results indicate that, due to the mismatch of acoustic impedance, the way of jet formation in heavy gas bubble with different species is diversified under the same initial condition. With respect to the same bubble, the manner of jet formation is also distinctly different under different shock strengths. The disparities of the acoustic impedance result in different effects of shock focusing in the bubble, and different behaviors of shock wave inside and outside the bubble. The analyses of the wave pattern and the pressure variation indicate that the jet formation is closely associated with the pressure perturbation. Moreover, the analy- sis of the vorticity deposition, and comparisons of circulation and baroclinic torque show that the baroclinic vorticity also contributes to the jet formation. It is concluded that the pres- sure perturbation and baroclinic vorticity deposition are the two dominant factors for the jet formation in shock-heavy gas bubble interaction.
