Evolution of Deviations from the Spherical Shape of a Vapor Bubble in Supercompression
R. I. Nigmatulin1,2, A. A. Aganin3, M. A. Il'gamov4, D. Yu. Toporkov3
1Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, 117997 Russia
2Lomonosov Moscow State University, Moscow, 119991 Russia
3Institute of Mechanics and Engineering, Russian Academy of Sciences, Kazan', 420111 Russia
4Mavlyutov Institute of Mechanics, Russian Academy of Sciences, Ufa, 450054 Russia
Keywords: bubble dynamics, spherical shape stability, acoustic cavitation, bubble collapse
Abstract
This paper considers the evolution of small deviations of a cavitation bubble from a spherical shape during its single compression under conditions of experiments on acoustic cavitation of deuterated acetone. Vapor motion in the bubble and the surrounding liquid is defined as a superposition of the spherical component and its non-spherical perturbation. The spherical component is described taking into account the nonstationary heat conductivity of the liquid and vapor and the nonequilibrium nature of the vaporization and condensation on the interface. At the beginning of the compression process, the vapor in the bubble is considered an ideal gas with a nearly uniform pressure. In the simulation of the high-rate compression stage, realistic equations of state are used. The non-spherical component of motion is described taking into account the effect of liquid viscosity, surface tension, vapor density in the bubble, and nonuniformity of its pressure. Estimates are obtained for the amplitude of small perturbations (in the form of harmonics of degree n = 2, 3,… with the wavelength λ = 2π R/n, where R is the bubble radius) of the spherical shape of the bubble during its compression until reaching extreme values of pressure, density, and temperature. These results are of interest in the study of bubble fusion since the non-sphericity of the bubble prevents its strong compression.
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