水下连发射弹的超空泡流动特性研究

基于Fluent流体仿真软件，采用用户自定义函数控制的动网格技术，对水下连发射弹的超空泡流场进行了数值模拟。通过与1组实验工况的比较，证实了所采用的数值模拟计算方法的可靠性。分析了两连发和3连发射弹情况下，超空泡流场的相互作用及其变化机理；得出了射弹超空泡无量纲长度在超空泡流场作用下的变化特点，计算出了流场的速度变化曲线和速度矢量等。研究结果表明：两射弹间的超空泡融合后，会在超空泡尾部区产生高速回射流并产生大量旋涡。这些旋涡引起的扰动能致使后续超空泡快速溃灭，表明了超空泡的极其不稳定性。后面的射弹进入前面射弹的空泡内后，其阻力系数达到最小值。当两连发超空泡射弹通过扰动区域时，前后超空泡都受到干扰，从而造成了它们的阻力系数增减。

Research on the Characteristics of Supercavitating Flows Caused by Underwater Continuously Fired Projectiles

Based on the FLUENT software and the dynamic grid technology controlled by user-defined function, the supercavitation flows of the continuously fired projectiles were numerically studied to analyze the characteristics of supercavitating flows. The numerical results of the supercavity shape and the drag coefficient of projectiles are effectively consistent with the experimental results, which indicates that the numerical simulation is exact, and the drag coefficient of projectile presents an increasing trend with the decrease in velocity of projectile. The mechanisms of supercavitations of two and three continuously fired projectiles are studied. The change rule of non-dimensional length is concluded, and the variation curve of velocity in flow field and the velocity vector are analyzed. The results show that, after the supercavity fusion of two projectiles, a high velocity re-entrant jet and many vortices are found in the aft of supercavitation. The vortices can lead to the rapid collapse of projectile supercavitation, which also indicates the extreme instability of supercavitation. The drag coefficient of two projectiles can reach to the minimum value when the two projectiles enter in a supercavitation. When the supercavitations of two continuously fired projectiles pass through the disturbance field, the supercavitations are disturbed, thus resulting in the increase and decrease in their drag coefficients.