Transient dynamic analysis for the ventilated supercavity under the action of tail jetting flow

Ventilated cavitation could be applied to underwater vehicles to achieve a high drag-reduction ratio. The ventilated supercavity may experience deformation, fluctuation, and instability under the influence of the high-speed jetting flow generated by the propulsion system. This study focuses on understanding the transient dynamics of a ventilated supercavity with jetting flow at the tail. Experiments are performed in an open water tunnel system with a high degassing rate. The evolution of the gas-liquid interface under different jetting flow rates is recorded in detail. A compressible multiphase model coupled with shear stress turbulence (SST) and surface capturing models is adopted herein to study the flow pattern in depth. As the jet velocity increases from subsonic to sonic speed, the flow field presents three different modes that could be identified as the transparent cavity (TC), transparent cavity-jetting (TC-J), and deformed cavity-jetting (DC-J) modes. A new gas shedding scheme that couples twin-vortex shedding with surface fluctuation shedding is observed in the TC mode. The variations in the internal flow structure and the local pressure vibration are discussed in detail. The transition of the flow pattern with dimensionless jetting momentum ratio and kinetic energy ratio is obtained. The obtained results could provide valuable insights into the control of the ventilated supercavity.