超声作用下水中微气泡的运动特性

Motion Characteristics of Microbubble in Water Under Ultrasonic Effec

超声促晶过程中,水或溶液中气体微泡的运动特性对结晶过程具有重要影响。建立了水中单个气泡的运动方程,讨论了各种力学因子和气泡粒径对单气泡上浮的影响;重点研究了气泡在外加超声波作用下,气泡粒径的变化规律以及气泡的运动特性。研究结果表明:静水中气泡的上浮速度随时间增加而逐渐增大,上浮初始阶段必须考虑由于加速度所引起的虚拟质量力和Basset力对上浮速度的影响;气泡上浮过程中其粒径越大则上浮速度越大;超声作用下,声压梯度力对气泡运动速度的影响强于其他力学影响因子,其速度变化与超声波发生规律一致;当气泡的初始位置处于超声场的不同位置处,气泡运动的方向相异,气泡具有上下两个方向的位移变化。

The motion characteristics of microbubble in water or solution have important influence on crystallization process due to ultrasonic. In this paper,the movement equation of single bubble was modeled based on force equilibrium. The efftect of a variety of mechanical factor and the diameter of the bubble on single bubble buoyancy was discussed. Furthermore,ultrasonic effect on motion characteristics of microbubble in water was focused on. The results show that the velocity of microbubble in static water is increasing with time increasing. The influence of virtual mass force and Basset force caused by the acceleration on the velocity of microbubble should be considered in the initial stage of microbubble motion. In the processes of microbubble rising,the diameter of the bubble is bigger,the floating velocity is higher. Under the action of ultrasonic,the influences of sound pressure gradient force are more powerful than other mechanical factors,and the velocity is varying with ultrasonic wave changing. In addition,the motion direction is opposite when the initial positions of bubbles are on the different positions of ultrasound,and so the displacements of bubbles moving up or down on two directions are found.