Experimental Study on Ventilated Cavity Flow at the Tail of Underwater Vehicle under Low Surface Tension

In model experiments, the Weber number determined by the surface tension usually has a significant effect on the ventilated cavity flow characteristics. This paper describes experiments in which the surface tension of water is reduced by adding surfactant, allowing thes flow characteristics of the ventilated cavity at the tail of an underwater vehicle under low surface tension to be analyzed. The effects of the Froude number, Weber number and cavitation number on the development of the ventilated tail cavity are explored. There are three stable closure modes of the ventilated cavity under low surface tension, namely, a complete foam cavity, partial foam cavity, and giant spindle cavity. The results show that a larger Froude number produces a smaller ventilated cavity, which mainly exhibits the complete foam cavity closure mode. A smaller cavitation number creates a larger ventilated cavity, which is mainly represented by the giant spindle cavity closure mode. The critical cavitation number under this closure mode is 2.19. At higher ventilation pressures, the entrainment ability at the end of the ventilated cavity is stronger, and bubbles are less likely to fall off.