STUDY ON IMPULSIVE PRESSURE OF A COLLAPSING CAVITATION BUBBLE. (EVALUATION OF THE EFFECT OF A WATER MICROJET).

Abstract

The motion of a spark-induced cavitation bubble is examined near a solid boundary by high-speed photography and the impulsive pressure generated at its collapse-reexpansion stage is detected by a local pressure sensor with four small sensor elements. As a result, the impulsive pressures of a shock wave and of a water microjet are separately measured by the local pressure sensor. The result is ascertained by high-speed photographs of the cavitation bubble, which indicate that a microjet is generated at the top surface of the collapsing bubble and collides against one of the pressure sensor elements through the interior of the bubble at its collapsing stage. Moreover, the diameter of the generated microjet tip and its travelling velocity through the interior of the bubble are evaluated to be about 0. 5 mm and 100 approximately equals 110 m/s, respectively.