Fundamental Understanding of Cavitation Phenomenon

为了更深入地了解空化现象，本文重点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。对二维薄板空化展开后的流场进行了观测和详细测量。得到了以下结论：1.无论空腔周围的分离边界层是否破裂，均可将空腔分为两种类型。相应地，用于数值分析的空腔模型应该有所不同。结果表明，翼面上的再入射流是产生云空化的主要原因。因此，可以通过在铝箔表面设置栅栏或沟渠等小障碍物来防止云中空化的产生。用于高温水(最高140℃)的小型空化隧道。是新建造和测试的。主要研究结果如下：1.在140度、14m/S的主流条件下，板式空腔的最大温降约为1.4度。当上游边界层因人为污染而增厚时，凹陷加剧。用Kato(1984)提出的Z因子进行的预测与实验结果相吻合。

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.