Hydrodynamic cavitation for sonochemical effects

A comparative study of hydrodynamic and acoustic cavitation has been made o n the basis of numerical solutions of the Rayleigh-Plesset equation. The bu bble/cavity behaviour has been studied under both acoustic and hydrodynamic cavitation conditions. The effect of varying pressure fields on the collap se of the cavity (sinusoidal for acoustic and linear for hydrodynamic) and also on the latter's dynamic behaviour has been studied. The variations of parameters such as initial cavity size, intensity of the acoustic field and irradiation frequency in the case of acoustic cavitation, and initial cavi ty size. final recovery pressure and time for pressure recovery in the case of hydrodynamic cavitation, have been found to have significant effects on cavity/bubble dynamics. The simulations reveal that the bubble/cavity coll apsing behaviour in the case of hydrodynamic cavitation is accompanied by a large number of pressure pulses of relatively smaller magnitude, compared with just one or two pulses under acoustic cavitation. It has been shown th at hydrodynamic cavitation offers greater control over operating parameters and the resultant cavitation intensity. Finally, a brief summary of the ex perimental results on the oxidation of aqueous KI solution with a hydrodyna mic cavitation set-up is given which supports the conclusion of this numeri cal study. The methodology presented allows one to manipulate and optimise of specific process, either physical or chemical. (C) 1999 Elsevier Science B.V. All rights reserved.