MODELING OF FREE-RADICALS PRODUCTION IN A COLLAPSING GAS-VAPOR BUBBLE

This paper deals with a model linking bubble dynamics under an acousti c pressure field and production of free radicals in the resulting coll apses of this bubble. The bubble dynamics model includes interdiffusio n of gas and vapour in the bubble as well as evaporation or condensati on at the interface, and it assumes uniformity of the internal pressur e and perfect gas law for the gas-vapour mixture. At the maximum compr ession of the bubble, all the reactions of dissociation which can occu r are assumed at thermodynamic equilibrium. The local composition (esp ecially in free radicals) in the bubble is then calculated by an algor ithm based on free energy minimization using the information concernin g the maximum compression provided by the bubble dynamics model resolu tion. Using this model a comparison of free radicals production has be en made for two different driving frequencies (20 kHz and 500 kHz), an d at given bubble radius and acoustic pressure, an optimum of liquid b ulk temperature has been derived for the production of free radicals v ery similar to the experimental one concerning oxidation reactions in aqueous phase. (C) 1997 Elsevier Science B.V.