高速カメラによる機械弁に生じるキャビテーション気泡の可視化

Abstract

Mechanical heart valves (MHV) are used as the prostheses for the patients who suffer the irreversible heart valve disorder. The cavitation occurs on MHV, and it could lead to the valve failure and also could damage blood cells. Therefore the cavitation on MHV should be analyzed in detail, and then its influence has to be minimized. In this study the images of the cavitation bubbles on the 20 mm Bjork-Shiley valve were captured using two high-speed cameras, ULTRA68 and ULTRA8 manufactured by nac Image Technology Inc. Soon after the valve closure the separate large bubbles were caused by the water hammer, and they grew up and shrunk within several microseconds. On the other hand, about 600 microseconds after the valve closure the squeeze flow generated the cluster of the innumerable minute bubbles, the cloud cavitation, which can erode the materials. This cloud cavitation existed for more than 200 microseconds. The results show that the different kinds of mechanisms contribute to the cavitation on MHV within only one millisecond after the valve closure.