Abstract
Power ultrasound is becoming a generally recognized tool in small-scale laboratory. It has considerable potential for industrial use. Actually, propagation of ultrasound wave (from 20 to 800 kHz) through a liquid inside a cylindrical reactor initiates acoustic cavitation and fluid dynamics phenomena. Acoustic cavitation is the formation and activity of bubbles in a liquid due local negative pressures. Spectacular effects including: erosion, sonoluminescence, molecular damage and chemical effects occur. Traveling power ultrasound also initiates fluid dynamics phenomena such as free surface deformations (aerosol formation), convection (macro-mixing), acoustic streaming (micro-mixing), … Characterization of the wave field formation is of significant importance for understanding phenomena and designing and optimizing industrial reactors. Mathematical modeling is here of a great interest, because the scale-up difficulties of ultrasound-based processes. Then, two-phase models (bubbles in liquid) are shown necessary, because bubble clouds interact directly with ultrasound propagation and modify the pressure field establishment. The cavitation field is so dense that it could play the role of an acoustic screen. Bubbles dynamic is considered and simple models are derived. Results show the influence of a homogeneous density distribution of bubbles on the wave attenuation and the agreement between the transient bubble motion induced by pressure gradients and visualizations.
