Observation of Inception of Sheet Cavitation from Free Nuclei

作     者：Wakana TSURU Takafumi KONISHI Satoshi WATANABE Shin-ichi TSUDA 

作者机构：Graduate School of Engineering Kyushu University Japan Department of Mechanical Engineering Kyushu University Japan 

出 版 物：《Journal of Thermal Science》 (热科学学报（英文版）)

年 卷 期：2017年第26卷第3期

页      面：223-228页

核心收录：

学科分类：080704[工学-流体机械及工程] 080103[工学-流体力学] 08[工学] 0807[工学-动力工程及工程热物理] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 0801[工学-力学（可授工学、理学学位）] 

基　　金：Japan Society for the Promotion of Science  JSPS  (17J04154) 

主　　题：成穴开始 表洞 原子核分发 溶解空气 

摘      要：Prediction of inception of sheet cavitation on solid walls has been recognized to be very difficult, since it is significantly affected by the boundary layer flow characteristics, the population of free nuclei, the nuclei held in the wall roughness, the amount of dissolved air in liquid and so on. It has not sufficiently been made clear how the inception is affected by the conditions of water qualities and background flow characteristics. In this study, high speed observation of inception of sheet cavity from free nuclei is conducted for a two-dimensional convergent-divergent nozzle flow, where the sheet cavity forms just downstream of the nozzle throat. The effects of the amount of dissolved air and the free stream velocity on the inception process of sheet cavitation is examined. In addition, the bubble nuclei density, which is well known to be important factor for cavitation inception, is passively controlled by the filter installed in the tunnel. From the observations, it is confirmed that the nuclei number density significantly affects the formation of sheet cavity rather than the other two parameters. In conditions with large nuclei number density, the sheet cavity does not form, and bubbly cavitation appears instead. In the case with small nuclei number density, the sheet cavity forms from a single flowing nucleus and develops streamwisely and spanwisely. In the conditions with medium nuclei number density, the sheet cavity also forms but is shorter/narrower streamwisely/spanwisely, due to interaction of other nuclei flowing near the formed sheet cavity.