Small non-sphericity of a convergent shock wave arising in a cavitation bubble in acetone during its collapse

Abstract

A numerical study of the features of the growth of small deformations of a radially-convergent shock wave in a collapsing cavitation bubble in acetone has been performed. The liquid temperature and pressure are 273.15 K and 15 bar, respectively. At the beginning of collapse, the bubble radius is 500 μm, the bubble is filled with the saturated vapor of acetone. The initial bubble non-sphericity in the form of the second, fourth and sixth spherical harmonics are considered. The dynamics of the vapor in the bubble and the surrounding liquid are governed by the axisymmetric gas dynamics equations closed by wide-range equations of state. The bubble surface is explicitly traced. It is shown that the small non-sphericity of the shock wave during its convergence, similarly to that of the surface of a bubble during its collapse, increases with decreasing its radius in the form of oscillations with growing amplitude. Moreover, the dependence of the increase in the amplitude of those oscillations on the radius of the shock wave in the interval from its formation to its reaching the “hot” bubble nucleus with a radius r < 0.25 μm, can be described by a power law with an index of -1.18.