Experimental study of the shock generation at the collapse of cavitation bubble

Using a photoelastic apparatus of Schlieren interferometer, an experimental study was conducted of the mechanism of the impulsive force generation by a spark-induced cavitation bubble, collapsing near the solid boundary. The experimental results indicated that the cause of the impulsive force is classified by the parameter l, where l = (maximum bubble center distance from the solid boundary)/(maximum bubble radius). In case of l equal to or greater than 1.35, the shock waves are dominant and in case of l less than 1.35, the water microjet impingement is the main cause of the impulsive force. In a special case (l equal to or less than 1.24), both the shock waves and the water microjet are supposed to impact against the solid boundary. Even when an asymmetrically collapsing bubble rebounds, the shock waves are observed.