Experimental investigation of ventilated supercavitation with gas jet cavitator

Abstract

We conduct an experimental study of the ventilated supercavitation generated from gas jet cavitator [gas jet ventilated supercavitation (GJVS)] over a broad range of ventilation and flow conditions for two gas jet nozzle sizes. The experiments show that supercavity evolves across different cavity regimes with distinct patterns, i.e., bubbly flow, Stable Cavity (SC), Unstable Cavity (UC), and Jet Cavity (JC) with increasing ventilation rate. The supercavity transition is shown to be a result of the stagnation location of gas jet shifting from the potential core zone to the established turbulent flow zone of the jet as ventilation increases. The variation of supercavity regimes under a broad range of Froude numbers is compiled, and the map of supercavity regime transition shows similar trends for different Froude numbers and nozzle sizes. Compared to a disc cavitator, in the SC regime, the GJVS exhibits similar ventilation hysteresis with a significantly higher ventilation demand for the formation of a supercavity. The transitions from SC to UC and UC to JC are examined using the ratio of gas jet length to potential core length, which shows a variation across different Froude numbers and nozzle sizes. Moreover, the change of supercavity dimension upon increasing ventilation is examined for SC and JC regimes. In the SC regime, the maximum diameter of the supercavity and the corresponding cavitation number remain constant with increasing ventilation, similar to the case of a disc cavitator. In contrast, the maximum diameter and the cavitation number grow linearly upon an increase of ventilation in the JC regime.