Fundamental Understanding of Cavitation Phenomenon

为了更深入地理解空化现象，本文着重研究了空化与粘性流动的关系，以及空化的热力学效应和内部流动，并对二维翼型的片状空化进行了流场观察和详细测量。得出以下结论：1。将空泡分为空泡周围分离边界层破裂和空泡周围分离边界层未破裂两种类型。相应地，数值分析所采用的空穴模型也应该有所不同.结果表明，云状空化的产生是由于在翼型表面逆流的重入射流引起的。因此，在翼型表面设置栅栏或沟渠等小障碍物可以防止云状空化的产生。是新建成并经过测试的。主要研究结果如下：1.在140 °和14 m/s的主流下，在发展的板腔中的最大温降约为1.4 °。随着上游边界层厚度的增加，下沉量也随之增加.用Kato（1984）提出的Z因子进行预测，与实验结果吻合较好。

This research has been made to understand cavitation phenomenon more deeply, focusing on (a) relation between cavitation and viscous flow, and (b) thermodynamic effect and internal flow of cavity.Observation and detailed measurement of flow field were made on developed sheet cavitation of a 2D foil section. Following conclusions were obtained :1. The sheet cavity was classified into two types whether the separated boundary layr around the cavity bursted or not. Accordingly, the cavity model for numerical analysis should be different.2. It was confirmed that generation of cloud cavitation was caused by re-entrant jet, which flowed upstream on the foil surface. Therefore, the generation of cloud cavitation could be prevented by a small obstacle such as fence or ditch on the foil surface.A small cavitation tunnel for high-temperature water (up to 140 deg.) was newly constructed and tested. The results were summarized as follows :1. The maximum temperature depression was about 1.4 degree in a developed sheet cavity at 140 degrees and 14 m/s of main flow. The depression was increased when the upstream boundary layr became thicker by manipuration.2. The prediction using Z-factor which was proposed by Kato (1984), agreed with experimental result.