چكيده به لاتين
In this study, acoustic pressure and acoustic streaming by using the finite element method in the reactor system of horn was investigated. After validation of simulation results by PIV data, investigation on geometry of the reactor and operating condition of the system like input power was done. For small to moderate pressure amplitudes the bubble radius will increase and decrease concomitantly with the decrease and increase of the acoustic pressure. However, for high intensity field, where the amplitude of the acoustic wave is higher or equal than the Blake threshold, inertial bubbles will exhibit a manifold volume increase followed by a dramatically sharp compression usually referred as bubble collapse. The collapsing process can be considered as an adiabatic process because the time scale of heat diffusion is longer than the time of the radial movement of the bubble wall. The acoustic cavitation threshold for both water and toluene was obtained and based on this pressure and the acoustic pressure in the reactor, active regions for cavitation was recognized. Based on the pressure in the active regions, the fluctuation of gas bubbles under the action of ultrasonic irradiation was represented by solving the keller-miksis equation with heat and mass transfer. The pressure and temperature that these bubbles reach when they collapsed, was calculated. Osilation of the bubbles in these regions and also variation of the water vapor molecules in the bubbles was determined. Four analytical ways were employed in order to obtain the reasonable results: (i) using the modified keller-miksis model to indicate the microbubbles behavior and their characteristic under the ultrasound radiation; (ii) using the Helmholtz equation with out of plane wave number in the CFD simulation in order to study the distribution of pressure within the reactor; (iii) using the momentum equation and turbulent equation to simulate the acoustic streaming in the comsol; (iv) using PIV analysis to confirm the simulation results; (vi) using calorimetric method for calculating the quantities of power that distributed in the reactor.
Keywords: acoustic cavitation, CFD simulation, sonoreactor, dynamics and cavitation bubble collapse
