Numerical investigation of planar shock wave impinging on spherical gas bubble with different densities

Abstract

The interaction between a planar shock wave and a spherical gas bubble containing sulfur hexafluoride, Refrigerant-22, neon, or helium is studied numerically. Influences of the Atwood number (At) on the evolution of the shock wave and gas bubble are clarified by using high-resolution computational simulations. The results show that the difference in the physical properties between the ambient air and the gas bubble has a significant influence on the evolution of wave pattern and bubble deformation. For the fast/slow configuration (At > 0) in the present study (At = 0.67 and 0.51), the incident shock focuses near the interior right interface to form an outward jet. Besides, the mixedness, average vorticity, and the absolute value of circulation all increase as the Atwood number increases. By contrast, for the slow/fast configuration (At < 0) with At = −0.19 and −0.76, the rotational directions of the vorticities formed at the same position are reversed compared with those in the fast/slow configuration, which induces an inward air jet to impact on the gas bubble from the outside. In addition, the mixedness, average vorticity, and the absolute value of circulation all increase as the Atwood number decreases. Nevertheless, regardless of At > 0 or At < 0, the effective volume of the gas bubble basically decreases when the Atwood number decreases. Hence, on the whole, the Atwood number has a nonmonotonic influence on the evolution of effective volume of gas bubble, mixedness, average vorticity, and circulation simultaneously.