基于双向流固耦合的超空泡射弹入水研究

超空泡射弹通过超空泡减阻技术在水下高速长距离航行, 是对抗水下近距离威胁的有效手段. 为了扩大防御范围、增加杀伤力, 超空泡射弹具有很高的发射速度. 高速超空泡射弹在入水时中受到极大的冲击载荷, 发生显著的结构变形, 结构变形与流场之间存在相互影响和作用, 常规的基于刚体假设的仿真研究方法不再适用. 为了研究高速超空泡射弹入水过程中的结构变形及其对流体动力特性的影响, 通过耦合流体力学求解器和结构动力学求解器, 建立了射弹高速入水双向流固耦合仿真模型, 并通过与文献中的试验结果进行对比验证了该模型空泡形态计算方法和耦合方法的准确性. 使用双向流固耦合的方法对高速射弹在不同初始攻角入水过程中的超空泡流动特性及结构变形特性进行了数值模拟研究, 通过对比流固耦合模型与刚体模型的计算结果, 得到了超空泡射弹的结构弯曲变形对流体动力载荷的影响. 研究结果表明: 高速射弹入水过程中流固耦合效应对超空泡流型及流体动力载荷的计算结果有显著影响; 本文所研究的射弹在考虑流固耦合效应, 带攻角垂直入水两倍弹长的范围内, 超空泡射弹的流体动力载荷与弯曲变形之间形成正反馈; 高速超空泡射弹在入水过程中受到的流体动力载荷及弹体应力应变随入水初始攻角的增加显著增大, 研究对象在初速1400m/s的条件下入水时, 当初始攻角不超过2°时不存在结构安全性问题. 

NUMERICAL STUDY ON WATER ENTRY PROCESS OF SUPERCAVITATING PROJECTILE BY CONSIDERING BIDIRECTIONAL FLUID STRUCTURE INTERACTION EFFECT

Supercavitating projectiles travel underwater at high speed and long distances through the supercavitation drag reduction technology, which is an effective means to counter close-range underwater threats. In order to expand the defense range and increase the lethality, the supercavitating projectile has a high launch speed. The high-speed supercavitating projectile is subjected to a great impact load during water entry process, and a significant structural deformation occurs on the projectile. There is an interaction between the structural deformation and the flow field. Resultantly, the regular simulation research method based on the rigid body assumption is no longer applicable. To study the structural deformation of the high-speed supercavitating projectile and its influence on the hydrodynamic characteristics, a bidirectional fluid-structurer interaction simulation model of the high-speed projectile is established by coupling the fluid dynamics solver and the structural dynamics solver. The accuracy of the numerical method to calculate the supercavitation flow field and the fluid structure interaction are validated by comparing with the published results. Numerical simulation investigations on the supercavitation flow field and the structural deformation characteristics of the high-speed projectile during water entry at different initial angles of attack are carried out with the bidirectional fluid-structure interaction method. By comparing the calculation results of the fluid-structure interaction model and the rigid body model, the influence of structural bending deformation of the supercavitating projectile on its hydrodynamic load is obtained. Research results show that the fluid-structure interaction effect has a significant influence on the supercavity and hydrodynamic load. When considering the fluid-structure interaction effect, there is positive feedback between the hydrodynamic load and the bending deformation of the supercavitating projectiles; the stress, strain and the hydrodynamic load of high-speed supercavitating projectiles increase significantly with the increase of the initial angle of attack. The structure of the projectile is safe when the initial velocity is 1400 m/s and the initial angle of attack is below 2°.