Simulation of sonoreators accounting for dissipated power
Résumé
A sonoreactor is a volume of liquid enclosed by a vessel and in contact with one or more ultrasonic sources, generally piezoelectric transducers. As such, it pertains to acoustics problems but globally consistent models of such systems is still lacking. The liquid generally undergoes inertial cavitation, which renders linear acoustics invalid, even if the latter accounts for bubbles. A nonlinear acoustics model is therefore necessary to describes acoustic waves in the cavitating liquid, accounting properly for the mechanical energy dissipated by bubbles into heat. As the numerical resolution of such models at the spatial and temporal scales involved in sonoreactors experiments appears yet unfeasible, we proposed a decade ago a reduced, albeit nonlinear model which results in a nonlinear Helmholtz equation. Once coupled to physics of elastic solids and piezo-electricity, a complete sonoreactor can be modelled and quickly solved, each part obeying a mechanical energy conservation equation, which we recall here. By construction, our model conserves energy, allowing additions. Three examples are proposed, for which dissipated and active power are systematically computed. For the first configuration, comparison with experiment is done and reveals that our cavitating liquid model overestimates the consumed electrical power by a two-fold factor. The second raises the issue of modelling correctly sonoreactors described in the literature. The third gives prediction on a new type of transducer, allowing radial energy transfer by lateral boundaries.