Molecular dynamics simulations of cavitation bubble collapse and sonoluminescence

Abstract

The dynamics of the medium within a collapsing and rebounding cavitation bubble is investigated by means of molecular dynamics (MD) simulations adopting a hard sphere model for the species inside the bubble. The dynamics of the surrounding liquid (water) is modelled using a Rayleigh-Plesset (RP)-type equation coupled to the bubble interior by the gas pressure at the wall obtained from the MD calculations. Water vapour and vapour chemistry are included in the RP-MD model as well as mass and energy transfer through the bubble wall. The calculations reveal the evolution of temperature, density and pressure within a bubble at conditions typical of single-bubble sonoluminescence and predict how the particle numbers and densities of different vapour dissociation and reaction products in the bubble develop in space and time. Among the parameters varied are the sound pressure amplitude of a sonoluminescence bubble in water, the noble gas mixture in the bubble and the accommodation coefficients for mass and energy exchange through the bubble wall. Simulation particle numbers up to 10 million are used; most calculations, however, are performed with one million particles to save computer run time. Validation of the MD code was done by comparing MD results with solutions obtained by continuum mechanics calculations for the Euler equations.

Dynamics of laser-induced bubble pairs

“…Fujikawa & Akamatsu 1980;Prosperetti & Plesset 1984;Yasui 1997;Storey & Szeri 2000;Marek & Straub 2001;Müller et al 2009;Dreyer et al 2012;Lauer et al 2012;Schanz et al 2012;Ishiyama et al 2013;Zein, Hantke & Warnecke 2013;Lotfi, Vrabec & Fischer 2014). The simulations assume an initial bubble size larger than the laser plasma to arrive at the experimental maximum bubble radii.…”

“…Dynamics of laser-induced bubble pairs 707 et al 1992; Putterman & Weninger 2000;Akhatov et al 2001;Brenner, Hilgenfeldt & Lohse 2002;Suslick & Flannigan 2008;Lauterborn & Kurz 2010;Schanz et al 2012). However, spherical-bubble collapse requires isotropic bubble surroundings and inherent stability conditions to be fulfilled with respect to spherical shape (parametric and Rayleigh-Taylor instability) (Plesset 1954;Strube 1971;Hilgenfeldt, Lohse & Brenner 1996;Ohl, Lindau & Lauterborn 1998;Lauterborn et al 1999;Ohl et al 1999;Lin, Storey & Szeri 2002;Koch et al 2011).…”

Optimization of an augmented Prosperetti-Lezzi bubble model

“…Also, nonadiabatic conditions may be introduced approximately with a polytropic approximation, in which c is replaced by j, where 1 < j < c (Leighton, 1994); however, this raises the problem of choosing a value for j. Equation (32) without the gas-inertia term may be used in conjunction with highly complex treatments of internal processes, such as that of Schanz et al (2012), in which a variant of the KK equation is employed. What cannot be accommodated is bubble departure from sphericity, which constitutes an enormous increase in complexity.…”

High-performance GPU computations in nonlinear dynamics: an efficient tool for new discoveries

“…The first test model is the periodically excited Keller-Miksis equation that is a second order ordinary differential equation describing the radial pulsation of a single spherical gas bubble placed in an infinite domain of liquid [38]. During the radial oscillation of the bubble, due to the external forcing, its contraction phase can be so rapid (collapse) that the temperature inside can reach thousands of degrees of Kelvin inducing chemical reactions [39][40][41]. Therefore, this model is extensively used in the field of sonochemistry [42][43][44][45][46][47][48][49][50][51] to estimate the collapse strength and the chemical yield of a single bubble.…”