Peer-Reviewed Publications
SHOCK-WAVE MODEL OF ACOUSTIC CAVITATION
Sergei Peshkovsky, Alexey Peshkovsky, Ultrasonics Sonochemistry, Volume 15, Issue 4, April 2008, Pages 618-628
Abstract
Shock-wave model of liquid cavitation due to an acoustic wave was developed, showing how the primary energy of an acoustic radiator is absorbed in the cavitation region owing to the formation of spherical shock-waves inside each gas bubble. The model is based on the concept of a hypothetical spatial wave moving through the cavitation region. It permits using the classical system of Rankine–Hugoniot equations to calculate the total energy absorbed in the cavitation region. Additionally, the model makes it possible to explain some newly discovered properties of acoustic cavitation that occur at extremely high oscillatory velocities of the radiators, at which the mode of bubble oscillation changes and the bubble behavior approaches that of an empty Rayleigh cavity. Experimental verification of the proposed model was conducted using an acoustic calorimeter with a set of barbell horns. The maximum amplitude of the oscillatory velocity of the horns’ radiating surfaces was 17 m/s. Static pressure in the calorimeter was varied in the range from 1 to 5 bars. The experimental data and the results of the calculations according to the proposed model were in good agreement. Simple algebraic expressions that follow from the model can be used for engineering calculations of the energy parameters of the ultrasonic radiators used in sonochemical reactors.
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MATCHING A TRANSDUCER TO WATER AT CAVITATION - ACOUSTIC HORN DESIGN PRINCIPLES
Sergei Peshkovsky, Alexey Peshkovsky, Ultrasonics Sonochemistry Volume 14, Issue 3, March 2007, Pages 314-322
Abstract
High-power ultrasound for several decades has been an integral part of many industrial processes conducted in aqueous solutions. Maximizing the transfer efficiency of the acoustic energy between electromechanical transducers and water at cavitation is crucial when designing industrial ultrasonic reactors with large active volumes. This can be achieved by matching the acoustic impedances of transducers to water at cavitation using appropriately designed ultrasonic horns. In the present work, a set of criteria characterizing the matching capabilities of ultrasonic horns is developed. It is shown that none of the commonly used tapered-shape horns can achieve the necessary conditions. An analytical method for designing five-element acoustic horns with the desirable matching properties is introduced, and five novel types of such horns, most suitable for practical applications, are proposed. An evaluation of the horns’ performance is presented in a set of experiments, demonstrating the validity of the developed theoretical methodology. Power transfer efficiency increase by almost an order of magnitude is shown to be possible with the presented horn designs, as compared to those traditionally utilized.
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