Study On The Water Exit Process Of Cylinder Based On The Ventilation Mode Of Head

When the submarine-launched missile is launched,the higher ejection speed will cause the appearance of shoulder cavities and damage the structure of the projectile,which will seriously affect the stability of the underwater navigation attitude and the reliability of the structure.When the missile crosses the water,the density of the medium changes suddenly,and the different fluid forces and moments cause the instability of the missile body’s attitude.Artificial ventilation makes the projectile encapsulated in the cavity,avoiding the sudden change of the medium density,and the change of the projectile posture caused by the collapse of the cavitation when the projectile crosses the water surface.The research on the water exit process of missile with ventilated supercavity can effectively provide guidance for the design of submarine launched weapon.In this paper,the method of numerical simulation is used to study the underwater movement and water exit process of the cylinder which has the ventilation mode of head with porous medium.The main research contents are as follows:The overlapping grid and six-degree-of-freedom motion method in the STAR-CCM+software has been exploited.The accuracy of the numerical calculation method in this paper is verified by comparing the speed of simulation and experiments,including the sphere free water discharge experiment and the head ventilation experiment of constant volume cylinder.The calculation parameters are determined for calculating numerical examples of different grid numbers,time step size,and calculation domain size.The water exit process of cylinder under vertical and tilt launch is calculated whether the ventilation mode of head exist or not.Compared with the cylinder without the ventilation mode,the cylinder which has the ventilation mode of head with porous medium suffers less viscous resistance,slower speed decline,longer total range,smaller horizontal displacement of the centroid and deflection angle,which proves that the head ventilation mode has a good effect on the attitude stability of the cylinder.The motion process of the cylinder under the conditions of vertical launch,multi angle and specific angle launch is calculated respectively,The underwater motion and water exit process of the cylinder under five factors,including ventilation pressure,porosity of the porous medium,initial velocity of the cylinder,direction and size of the cross flow velocity,and the launch angle,are studied.The variation of cavitation shape and pressure coefficient distribution at different moments are described,giving the time-varying curves of viscous resistance,velocity,total range,horizontal displacement of centroid,and deflection angle,the laws of multiple factors affecting the attitude change of cylinder are obtained.