不同头型高速射弹垂直入水数值模拟

为研究不同射弹头型对高速射弹垂直入水的流体动力和流场特性的影响,采用有限体积法和VOF(volume of fluid)多相流模型,并引入动网格技术,对5种不同头型的轴对称高速射弹垂直入水过程进行了数值模拟,分析了头型对空泡形态演化过程、射弹流体动力及弹道特性的影响规律.研究结果表明,头型对射弹入水空泡形态、表面闭合时间以及入水阻力、深度、速度均有较大影响.球头与截球头空泡半径小于其余3种头型,表面闭合时刻依平头、球头、锥头、截锥头的顺序递增.射弹头部均承受较大压力,球头、截球头射弹头部压力分布不均使之承受较大的剪切力.射弹头部流线型越好,入水速度衰减越慢,入水深度增加越快.入水阻力系数峰值按平头、截球头、截锥头、锥头、球头的顺序递减.

Numerical simulation of vertical high-speed water entry process of projectiles with different heads

The finite volume method, VOF (volume of fluid) multiphase flow model, and dynamic grid technique were introduced in order to conduct the numerical simulation of vertical high-speed water entry process of axisymmetric projectiles with five different heads. The influences of the head types on the cavity shape, the projectile hodrodynamics and trajectory properties were studied. The results show that the head type has significant influences on the cavity shapes, surface closing time of cavities, resistance, depth and speed of water entry process. The radius of the cavity induced by sphere and truncated sphere projectiles is smaller than that of the projectiles with the other three head types. The surface closing time decreases in the order of flat head, sphere head, cone head and truncated cone head. The pressure on the projectiles is pretty high and the distribution of the pressure on the sphere or truncated sphere head is uneven so that high shear stress exists on these heads. The water entry velocity decreases more slowly and the depth increases more quickly as the projectile head has a better streamline. The drag coefficient decreases in the order of flat head, truncated sphere head, truncated cone head, cone head, sphere head.