Numerical Simulation Of Ventilation Cavitation Flow In Supercavitating Vehicle With External Strut Structure

In recent years,the application of supercavitation technology in high-speed surface vehicle has received extensive attention.The supercavitating high-speed surface vehicle or craft connects two torpedo-shaped sub-water bodies through the strut structure,so that the surface of the sub-water bodies are covered by the entire cavity.In this way,the sub-water bodies does not directly contact with the water,so the resistance during navigation is reduced and the speed is increased.Unlike traditional supercavitating underwater vehicle,this kind of high speed surface vehicle limited by power unit leading to a lower speed,and the supercavity generated by ventilation is obviously affected by gravity and has poor stability.The strut structure will affect the shape of the cavity and thus affect the hydrodynamic performance of the vehicle.Therefore,it is an urgent problem to study how to optimally generate ventilated supercavity for the high-speed surface vehicle with strut structure.Based on the above problems and considering the complexity of the flow field around the strut,this paper studies the ventilated supercavitating flow of the high-speed vehicle with strut structure through numerical simulation.The main research contents are as follows:The VOF multiphase flow model and the SST turbulence model are used to study the effect of the strut on the ventilated cavity flow.The experimental model with middle support in the water tunnel experiment was numerically simulated.The change of the cavity shape under different ventilation rates was obtained.Our research combines the known experimental results to verify the gas entrainment after the support of the model.Considering the existence of free liquid surface,the influence of the strut on the cavity flow field and the change of the vehicle drag coefficient are discussed when the three variables of sailing inclination,navigation depth and navigation speed are changed respectively.For the struts with different cross-section shapes,the changes of cavity shape and hydrodynamics under the same working conditions are discussed.According to the double-cavity flow pattern,the drag reduction scheme of the parallel supercavity in the vehicle body is proposed.In this study,the generated way of ventilated cavities in supercavitating bodies with external strut structures was improved.By providing an half ring type cavitator both sides of the strut,the influence of the dramatic change of the pressure field on the leading edge of the strut on the cavitation flow is avoided;By setting upmultiple half ring type cavitators along the axis of the vehicle to generate parallel supercavity,the floating and fluctuation in the single bubble are avoided due to the buoyancy effect and the large value of ?.A numerical simulation of ventilated cavity generated by the strut was studied.In order to further reduce the resistance of the strut,cavities are generated by installing gas ventilation ports and cavitators on the strut.The interference of the cavities generated by the strut and the sub-water body was studied when the ventilation rates and the position of the cavitators were different.A comparison was made between the conditions in which the cavitator generates a ventilated cavity on the strut and ventilation without cavitator.The results show that the scheme of ventilation without cavitator on the strut has the least interference to the cavity of the vehicle body.Through a large number of numerical simulation and analysis of the flow mechanism of the ventilated supercavity in the supercavitating sub-water body with strut structure,this research provides a meaningful reference for the design of supercavitating high-speed surface vehicle.