A viable method to predict acoustic streaming in presence of cavitation.
The steady liquid flow observed under ultrasonic emitters generating acoustic cavitation can be successfully predicted by a standard turbulent flow calculation. The flow is driven by the classical averaged volumetric force density calculated from the acoustic field, but the inertial term in Navier-Stokes equations must be kept, and a turbulent solution must be sought. The acoustic field must be computed with a realistic model, properly accounting for dissipation by the cavitation bubbles [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Comparison with 20kHz experiments, involving the combination of acoustic streaming and a perpendicular forced flow in a duct, shows reasonably good agreement. Moreover, the persistence of the cavitation effects on the wall facing the emitter, in spite of the deflection of the streaming jet, is correctly reproduced by the model. It is also shown that predictions based either on linear acoustics with the correct turbulent solution, or with Louisnard's model with Eckart-Nyborg's theory yields unrealistic results.
Centre RAPSODEE, UMR CNRS 5302, Université de Toulouse, Ecole des Mines d'Albi, 81013 Albi Cedex 09, France. Electronic address: louisnar@enstimac.fr.
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Louisnard
Acoustic cavitation; Acoustic streaming; Bjerknes force; Propagation in bubbly liquids