Study On Cavity Evolution And Load Characteristics Of Water Exit Of Underwater Vehicle Constrained By Ice Environment

The water exit of the vehicle has the characteristics of high turbulence,strong nonlinearity,multiphase flow and complex special environmental hydrodynamics.This process is a typical problem of unsteady cavitation flow and its coupling with wall and free surface.The unstable evolution of cavitation,including fracture,shedding,etc.,will affect the motion characteristics of the vehicle.The low temperature conditions in the polar regions and the existence of ice make the process of traversing the water surface more complicated.Therefore,the multi-phase flow characteristics and load characteristics of water exit have a significant engineering application background and research value.In this paper,a combination of numerical calculation and experiment is used to study the characteristics of cavitation multiphase flow in the polar ice environment of water exit.First,the separation eddy simulation(DES)method and the volume of fluid domain(VOF)are used to capture the gas-liquid interface,and the Schnerr-Sauer cavitation model is used to simulate the cavitation mobile phase transition process.We compared with the experimental results to verify the effectiveness of the numerical method,and established a numerical prediction model of unsteady cavitation flow.On this basis,we carry out research on the evolution characteristics of natural cavitation at low temperatures.First,the characteristics of cavitation evolution and pressure pulsation at 0 ℃ and 25 ℃ are analyzed.The evolution of cavitation and pressure pulsation at 0 ℃ are more severe.Secondly,analyzing the cavitation shedding frequency,periodic characteristics and vortex structure characteristics at low temperatures.Secondly,we will deeply explore the influence of ice on the cavitation evolution of ventilating cavitation.First,based on the numerical simulation method established in Chapter2,the validity of the numerical method of ventilating cavitation is verified.We analyze the influence of ice on the evolution characteristics of ventilating cavitation,and mainly study the evolution of ice on cavitation and flow field characteristics.Secondly,discussing the influence of the presence or absence of single ice on the ventilating cavitation vortex structure and the closing of the wake field.Finally,the influence of ice on the pressure fluctuation and the load characteristics of the vehicle is analyzed.Next,in order to explore the cavitation evolution and load characteristics of the vehicle.The method of experiment was adopted to study the effect of the underwater vehicle’s water exit and different ice structures.We compared the effects of different shapes of ice on cavity evolution,motion characteristics,pressure changes and load characteristics,and focused on the analysis of the effects of floating ice and crushed ice on the evolution of cavitation.The presence of ice destroys the cavitation shape of the water exit,changes the load characteristics of the water outlet process,and reduces the additional mass of the vehicle.The change of the aperture affects the pressure pulsation trend during the water exit of the vehicle.Finally,we use the two-way fluid-solid coupling method to analyze the evolution characteristics of the water exit cavity and the flow field changes of the vehicle.We use numerical simulation to compare the impact of the existence of floating ice on the process of vehicle water exit.We focus on the analysis of cavity evolution,the interaction of cavitation and free liquid surface,and the stress distribution characteristics of the surface of the vehicle.The results show that the stress distribution on the surface of the vehicle without ice has greater fluctuation.