超声场中液体材料的空化和声流动力学研究进展

Progress of cavitation and acoustic streaming dynamics of liquid materials within ultrasonic field

高强超声在液体中传播所产生的空化和声流效应能够有效调控传热传质过程,因此在材料制备和成形过程中具有广阔的应用前景.由于合金熔体的不透明性导致无法直接实验观察超声作用机制,数值模拟方法成为全面分析超声传播特性及其对合金凝固作用规律的有效途径.本文首先综述了超声传播方程由线性模型向非线性模型的演变历程,并总结了超声功率、变幅杆半径、容器几何形状和超声维度等因素对声压和声流分布的作用规律.其次,介绍了单泡和多泡体系中的超声空化动力学模拟结果,包括各种参量对气泡振荡过程的调控、非球形气泡失稳机制、气泡间的相互作用以及超声空化对液体中温度和压强的作用机理.然后,将超声空化和声流的数值模拟与金属凝固过程相结合,介绍了多种模拟超声凝固的宏观和微观数值模型,并系统总结了超声空化和声流效应对晶体形核生长和流动传热的作用机制.最后,对该领域的未来研究方向进行了展望.

Power ultrasound can effectively control the heat and mass transfer processes in liquids due to its cavitation and acoustic streaming effects,leading to a broad application prospect in the field of material preparation.Due to the opacity of alloy melt,it is impossible to observe the ultrasonic process directly in experiment,and numerical simulation becomes an important method to fully analyze the propagation characteristics of ultrasonic and its effect on alloy solidification.This overview firstly summarizes the evolution of sound propagation equation from linear model to non-linear model and the modification mechanisms of ultrasonic power,sonotrode size,container shape and ultrasonic dimension on sound pressure and acoustic streaming.Besides,the numerical simulation results of cavitation dynamics in single and multiple bubble systems is introduced,including bubble instability mechanism,bubbles interaction and the effect of cavitation on the liquid pressure and temperature.Furthermore,by combining ultrasonic cavitation and acoustic streaming dynamics with metal solidification process,several macro-models and micro-models to simulate ultrasonic solidification is presented,and the mechanisms of ultrasonic cavitation and acoustic streaming on crystal nucleation growth,heat transfer and liquid flow are systematically summarized.Finally,a concise perspective is provided for its future advances.