粒子法によるクラウドキャビテーションの２次元非定常挙動と衝撃波の発生・伝播の数値解析

抄録

It is known that cloud of cavitation bubbles shows a collective unsteady behavior repeating the process of growth and collapse. In particular, it is considered that a high-pressure shock wave is emitted when the cloud collapses and leads serious problems such as erosions in fluid machinery. Much effort has been made in numerical studies where the notion of clouds is known as an aggregate of tiny spherical bubbles and the internal phenomena of the cloud have been investigated. However, the rigorous definition of clouds is vague and one has not clarified how the cloud can be generated in multiphase flows nor how the intensive shock wave is generated to propagate associated with the collapse of the cloud. In this study, we make a two-dimensional numerical analysis of a submerged bubbly water-jet injection into still water by using the standard SPH method based on the mixture model of liquid and gas bubbles. Then, we numerically observe how clouds can be formed to perform the unsteady behavior and also how the shock waves can be induced by the collapse of the cloud. Finally, we show that an intensive shock pressure is generated almost at the same time as the collapse of the cloud and the shock wave propagates from the collapse point with sonic speed of the medium.