Analysis On The Tail Cavitation Evolution Mechanism And Loading Characteristics Of The Water-exit Vehicle

When the submersible vehicle is launched,the high-pressure driving vehicle inside the launcher leaves the launcher and enters the atmosphere through the water medium.After the tail of the vehicle leaves the launcher,the high-pressure gas gushing out of the launcher and breaks under the action of the surrounding water medium to form the tail cavitation of the attached body.The evolution of tail cavitation is an unsteady process in which the pressure changes greatly,and its evolution is very important to the stability of the water outlet and the dynamic characteristics of the vehicle.The existing researches on tail cavitation mainly focus on theoretical formula derivation or auxiliary research on the development of shoulder cavitation.The researches on the evolution process of tail cavitation of the vehicle as well as the internal flow of cavitation and the influence of the development of tail cavitation on the development of shoulder cavitation are relatively rare.In this paper,numerical simulation will be used to study the evolution mechanism of tail cavitation during outlet of two kinds of structures,the outlet power of the vessel and the coupling effect of shoulder and tail cavitation.First of all,the influence of air mass oscillation in the launcher is excluded in this paper,and the development status of the tail air mass and the load characteristics of the tail air mass are studied by using the one-way fluid-solid coupling method in the case of small cylinder pressure.The results show that the development of the cavitation at the tail of the vehicle is influenced by the extrusion of the surrounding water medium and the backward step flow on the surface of the vessel wall,and the backward step flow is more obvious with the tail skirt.The greater the sailing speed is,the more violent the pressure oscillation at the tail of the vehicle will be.Then,based on the analysis of unidirectional coupling,the evolution law,load characteristics and dynamic characteristics of the air mass at the tail of the vehicle under different working conditions under the pressure emission condition of large cylinder are studied by using the method of bidirectional fluid-solid coupling.The results show that the oscillation shedding of the air mass at the nozzle has great influence on the development of the tail cavitation,and the pressure of the air mass at the nozzle has great fluctuation under the conditions of large depth emission.Under the condition of small cylinder pressure emission,the tail pressure fluctuates obviously and the tail air mass falls off obviously.The tail pressure fluctuation of a tail skirt is obviously less than that of a tail skirt.Finally,in this paper,the study is to simplify the model,the static water conditions and have boat speed under the condition of active ventilation cavity and tail cavity coupling and dynamic characteristics,the results show that the bodies from the rear of the tube after high pressure gas fluctuation with wall to flow will cause the function of active ventilation cavity loss,bodies,the tail jet impact will cause the instability of the ventilation cavity loss,loss cavity and the development of cavitation added into the tail cavity to eliminate a closed cavity of expanding the occurrence of low pressure.Under the condition of cross flow,the rebound effect of the cavitation at the tail of the vehicle is weakened,and the development of the cavitation at the shoulder is hindered.