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Liquids at negative pressure
Author(s) -
Xiao C.,
Heyes D. M.,
Powles J. G.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200460392
Subject(s) - sonoluminescence , bubble , radius , recoil , cavitation , mechanics , molecular dynamics , equation of state , thermodynamics , amplitude , volume (thermodynamics) , kinetic energy , physics , chemistry , materials science , classical mechanics , atomic physics , optics , computational chemistry , computer security , computer science
We have further explored the final stages of the collapse of an unstable cavity or bubble using the Molecular Dynamics computer simulation technique. A nanometre sized spherical volume of molecules was removed from a bulk Lennard–Jones liquid, which being mechanically and thermodynamically unstable, proceeded to collapse. The molecules with the highest kinetic energy were the first to enter the initially empty cavity. The temperature of individual molecules inside the cavity, while the density was still typical of a gas, could reach at least an order of magnitude larger than that of the surrounding liquid, e.g., equivalent to 6,000 K for water, which is not unreasonable for the sonoluminescence effect to be seen. During the filling in of the cavity, the average temperature decreased, as the contents thermally equilibrated with the surrounding liquid. The bubble partially filled in, and then proceeded to partially empty again, and so on in an oscillatory manner, with ever decreasing amplitude towards the final uniform liquid state. This ‘recoil’ effect is predicted by classical hydrodynamic treatments and has been observed in experiment for much larger bubbles. The temperature, density and normal pressure component were resolved as a function of radius from the centre of the bubble at selected times during the collapsing process. The simulations support the view that MD can provide a realistic representation of the final stages of cavity collapse. It does not make assumptions about equation of state and transport coefficients as would be required for a comparable solution of the Navier–Stokes hydrodynamics equations, and is therefore an especially appropriate description for the final stages of the collapse. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)