Numerical Simulation Of Hollow Projectile Flow Field

As a new kind of supersonic ammunition,hollow projectiles have broad prospects in air-defense realm with the advantage of low-drag and high-velocity.Therefore,there’s a significance to investigate the flow fields of the hollow projectile.The numerical simulation is carried out with the employ of the correct viscous equations and the high-order AUSM+ scheme using CFD++ validated with typical cases.In order to develop a 30mm-diameter and 80mm-length hollow projectile,the paper studied its flow fields and aerodynamics systematically.The main contents and achievements of this dissertation are described as follows.There are two kinds flow situations emerging after simulating flow fields of hollow projectiles.One is the high-drag condition of chocking.On the other side,when the projectile obtains a high velocity,then there is no chocking occurred.The results show the elements which result in chocking can be divided into internal and external factors,respectively.The internal factors involve the area ratio of throat to inlet i,inlet angle θ and the leading edge thickness h;the external factors involve Mach number(Ma)and angle of attack(AOA).We choose two groups of reasonable shape to perform simulation at different Ma and AOA.The drag and lift of the hollow projectile were obtained.The results show that hollow projectiles are unfit for the flight at Ma=2.0 and below,which the chocking appears.The drag of projectile increased when AOA exceeds 3°,Meanwhile,the flow field turn to the chocking.A practical projectile is developed according to above criterion.Then,the sabot-separating flow fields were simulated,which indicated that the process impacts the projectile’s drag.In order to investigate the flow fields and aerodynamics in the sabot-discard process,overset grids were adopted to couple governing equations of fluid dynamics and rigid body motion equations of six degrees of freedom(6DOF)with two dimensional axisymmetric models.Our results also show that the drag of projectile fluctuates in the initial phase.The situation at Ma=2.5 is more complex.The time of air compression in hollow is reduced in high Ma number.The fluctuation calms down until the sabot moves away in a certain distance.