Numerical investigation of ventilated cavitating flow from high to low cavitation numbers

Abstract

Cavitation occurs when an underwater vehicle moves at a high speed, causing the water to change from the liquid phase into the vapour phase in the low-pressure region. As one of the most efficient drag reduction technologies for high-speed underwater vehicles, the artificially ventilated cavitation flow needs to be studied. In this paper, the ventilated cavitating flow over a high-speed underwater vehicle is analysed with a multi-phase solver from high to low natural cavitation numbers. The large eddy simulation turbulence model, volume of fluid method and Kunz cavitation model are used in the numerical calculation to simulate and capture the three-phase (air, liquid water, and vapour) cavitation flow. The miscibility of the air and vapour phases inside the cavity is also considered in the simulation. To validate the solver, two benchmark cases with air ventilated into a cavitating flow are simulated. Then the characteristics of the ventilated cavitating flows from a high to low natural cavitation number are analysed to study the development of the ventilated cavity with miscible air and vapour inside it. The results show that air ventilation can prevent pressure fluctuations at the surface of an underwater vehicle caused by cloud cavitating flow at a moderate natural cavitation number. Compared to no ventilation, drag reduction of ventilated cavitating flow can reach up to about 85% at a low cavitation number.