Force acting on a cylinder under ultrasonically induced cavitation

To elucidate mechanisms of cavitation action on a surface with microcapillary discontinuity and refine the model of the sonocapillary effect, the force acting on a cylinder is correlated with the height of a liquid in the capillary under cavitation, both quantities being measured at the same point of the ultrasonic field. It is found that the force acting on the cylinder is directed toward a cavitation cluster stabilized at the end face of the cylinder. This force can be enhanced with another cylinder placed on the side of the cluster coaxially with the first one. The dynamics of the cavitation cluster depending on the cylinder spacing is investigated in the case when one of the cylinders is on a pendulum suspension. The conditions for self-sustained oscillations of the pendulum are found. The dependence of the attracting force between the cylinders on the ultrasonic frequency and cylinder spacing is derived. The end-face-averaged pressure exerted on a cylinder of diameter 1.2 mm may reach 0.16 kPa, and the intracapillary pressure attains 0.89 kPa. Thus, the sonocapillary effect may be explained, at least partially, by a counterpressure arising from cluster-capillary interaction. This effect can be used in designing cavitation sensors and ultrasonic sources.