Numerical Study On The Flow Field Structure And Ballistic Characteristics In The Salvo Process Of Underwater Vehicles

Based on the development of multi-projectile salvo technology of submarinelaunched weapon,this paper studies the underwater salvo process of dual-vehicle under different launch parameters,using numerical simulation method.The main contents and conclusions of this paper are as follows:Firstly,the numerical research method of underwater launching process is established,using VOF multi-phase model and Realizable k-ε turbulence model.The underwater 6-DOF motion of vehicles is realized by overset grids method.A half-size numerical model and a full-size one are established to simulate the underwater salvo process of dual-vehicle.The structure of vortex in the flow field is extracted according to the Q-criterion,and the data obtained from the simulation result is nondimensionalized.Secondly,the flow separation near the wall of an undisturbed vehicle is studied under the typical conditions.The development of the wake vortex caused by flow separation is analyzed,and the disturbance characteristics of the flow field structure by single vehicle are studied.Due to the change of the attack angle in the motion process and the winding shape of the vehicle,the boundary layer on the surface is separated,and the wake vortex falls off from the bottom of the vehicle.The wake vortex falls off at a certain frequency in the motion process,forming a sequence of wake vortex in the flow field.The wake vortex caused by the vehicle are the main characteristics of the disturbance to the flow field structure.Then,the evolution of pressure distribution on the surface and hydrodynamic characteristics of vehicles under the typical condition are analyzed,and the influence of the wake field on the hydrodynamic force of the second vehicle is studied.The wake vortex caused by the first vehicle changes the pressure distribution in the flow field,and there is a minimum of the pressure field in the core region of wake vortex structure.Under the intervention of the wake field,the lift force and pitch moment of the second vehicle always deviate to the center of the wake area,and the fluid resistance is smaller than that of the undisturbed vehicle,which leads to a trend of acceleration.Finally,the simulation of underwater salvo process under different launch parameters is carried out,and the effects of launching time sequence,time interval,initial distance and platform layout on underwater trajectory and motion attitude of the second vehicle are compared and studied.It is found that the relationship between the trajectory and the launch parameters is non-linear.The trajectory and attitude of the second vehicle always deviate and deflect to the center of wake region during the motion process.The transverse relative position between the second vehicle and the wake region is the main factor that influences the interference between salvo vehicles.The motion process of the disturbed vehicle towards the center of wake region is essentially the transient process from unstable state to critical stable state.