Abstract

Characterisation of the Cavitation Field in an Ultrasonic Reactor

A.Moussatov, C.Granger, B.Dubus (Institut Superieur d'Electronique du Nord (IEMN departement ISEN, UMR CNRS 8520), Lille, France)

e-mail: Alexei.Moussatov@univ-lemans.fr

Most of laboratory processes activated by ultrasonic cavitation require scaling-up in order to develop effective industrial devices. For this purpose numerical models of cavitation field based on single bubble dynamics are difficult to implement. A different approach using a phenomenological model of ultrasonic cavitation field is proposed here. It considers the cavitating fluid in steady state as a nonlinear fluid whose characteristics (sound speed, density) depend upon the bubble density. The constitutive relationship between bubble density and acoustic pressure is obtained by experimental characterisation. A real-time measurement method of the bubble density, based upon the modulation of the electrical resistance of the fluid is developed. Nonlinear oscillations of the bubbles modulate the current density and therefore affect the impedance (mainly resistive) between two point electrodes. Spectral analysis of the current density amplitude is carried out. Experimental results on the characterisation of the cavitation field in a 20 kHz laboratory scale reactor are reported and discussed.

Section : 4