Numerical Simulation Of The Flow Field Induced By Vibrating Surface In The Application Of Ultrasonic Cavitation

Ultrasonic cavitation generated by high-frequency ultrasonic transduceris widely studied because this phenomenon could be applied in a great varietyof fields, including medical therapy, industrial cleaning as well as sewagetreatment. Ultrasonic cavitation in application of medical treatment,especially in the area of tumor therapy, has become research fronts. The highnonlinearity involved in the flow field induced by ultrasound adds to thedifficulty of theoretical analysis together with numerical simulation.Based on the method of CFD, the present study investigates the flowfeatures of the field influenced by vibrational boundary, at both low and highfrequencies. Three vibration patterns are established, i.e. piston movement,drumhead deformation and spherically self-focused vibration, and theresultant flow field is calculated. Moreover, boundaries vibrating at lowfrequency (10Hz-100Hz) as well as high frequency (1MHz) are simulated.The low frequency vibration is based on mechanical vibration with Volume ofFluid model describing the whole computational domain, and the highfrequency vibration represents that of an ultrasound source where cavitationmodel is used.In the simulation of moving boundary at the frequency range of10Hz to100Hz, the impact of different vibrating amplitudes and frequencies to thesurrounding flow is studied according to the numerically calculated results,including distributions of pressure and velocity. A mechanism structure isdesigned to realize the alternating motion of a piston on the experiment rigwhich is built on purpose of performing mechanical vibration at lowfrequencies. The Particle Image Velocimetry test is then conducted on theexperimental water tank. The velocity data acquired in experiment iscompared with the simulation results, which could well verify the validity andreliability of both the calculated distribution and the calculation method, i.e. the Dynamic Mesh method. Furthermore, the model of high frequencyvibration is studied where spherically self-focused vibrating surface serves asthe moving boundary. Simulation results show the induced flow field in waysof pressure distribution, velocity profile and cavitation parameter distribution.In data analysis and discussion, several important sections at various locationsare investigated, and thus the focusing effect and cavitation inception processcould be estimated accordingly. The conclusion is expected to be of someguidance to the actual ultrasonic cavitation experiment and clinical therapylater on.