INVESTIGATION ON THE IMPACT OF UNDERWATER VEHICLE HEAD SHAPES ON THE FLOW AND PRESSURE CHARACTERISTICS OF VENTILATED CAVITY UNDER VERTICAL EMISSION CONDITIONS

This paper aims to explore the impact of underwater vehicle head shapes on the evolution of ventilated cavity under vertical emission conditions. Firstly, based on the finite volume method, the numerical calculation model for ventilated cavitation under the vertical emission condition is established, in which the improved delayed detached eddy simulation, the volume of fluid multiphase flow model and the overlapping mesh technique are adopted. Subsequently, compared with the vertical emission experiments, the validity of the numerical method was confirmed for predicting ventilated cloudy cavity, which demonstrates the applicability of the method in the complex unsteady calculation. Finally, the study compares the flow and pressure characteristics of ventilated cavity of streamline head and blunt head vehicle under the same working conditions, and the reasons for the observed differences are analyzed from the perspective of vortex dynamics. The results indicates that, compared to streamlined-head vehicle, the ventilated cavity of the blunt-headed vehicle experiences a smaller velocity gradient at the gas-liquid interface and is more influenced by gravity and buoyancy, leading to an earlier nonlinear instability under the action of the Rayleigh-Taylor instability mechanism. Additionally, the cavity shows more dramatic unsteady flow characteristics, e.g. floating behavior and cavity shedding, which influence the flow separation at the end of the ventilated cavity of the blunt-headed vehicle, resulting in suppression of high amplitude characteristics of stagnation high pressure.