Numerical Design Study, Low Resistance Hollow Shells

There is a hollow along with the axis of the hollow projectile, which will make the projectile has the advantages of high launch speed and low drag. Therefore, it has broad application background in the ammunition field of air defense and the aircraft. In recent years, with the gradual maturing of the research technology of the hollow projectile, it will be one of the main projectiles used for small caliber cannons. Thus, it has vital significance for making researches on the hollow projectile.In this thesis, the hollow projectile with inner diameter of d=17.2mm, outer diameter D=30mm and length L=80mm, is used as our investigating object. After the choice of viscous control equations and AUSM scheme, a CFD software is employed to simulate numerically the normal hollow projectile field and its drag, the results have been validated. Then, based on the drag coefficient of hollow projectile, the aero shape of the hollow projectile has been optimized numerically, and the optimal shape with minimal drag has been obtained. And the flow fields under the condition of inflow Mach number Ma= 1.2～4.0 have been simulated, the variation rules of hollow projectile wave structures, pressure distribution and drag coefficient have been shown. The conclusion that the hollow projectile is only fit for high speed launch is obtained. At the same time, the flow field and drag of hollow field under both condition of viscous N-S and ideal Euler equations have been compared, we found that the proportion of viscous force for hollow projectile is large in the total drag force compared to the normal projectile, thus, the effect of viscous flow must be included for hollow projectile simulation. In addition, the flow field of hollow projectile under different angles of attack have also been simulated, the effects of angle of attack on the flow field and its drag have been discussed, When the angle of attack is larger than 4°, the drag increases quickly. Our above conclusions can provide important guidance for future further investigations on hollow projectiles.