EXPERIMENTAL STUDY ON CAVITATION STARTING AT AND FLOW CHARACTERISTICS CLOSE TO THE POINT OF SEPARATION

Microscopic bubbles stably existing everywhere in liquid are the core idea of the traditional nucleus theory for cavitation. However, the idea conflicts with the following two facts; one is diffusion, the universal physical law in nature. The other, which has experimentally been confirmed, is that a tensile stress generated in liquid does not cause any anticipated changes in liquid such as explosive growth of bubbles and reduction of sound velocity when it is propagated as a wave [1]. The present paper introduces the cavitation study in oil flows carried out by the present authors with the intention of answering these questions. Some interesting results discovered through observations of cavitation starting at the point of separation are provided together with their physical interpretations, which may be quite unfamiliar to many but are conceivably no less plausible than the nucleus theory as a hypothesis. The newest one is that the singularity of a flow separating from a wall can be the real cause of cavitation