基于全非线性边界元法的楔形体入水冲击载荷特性研究  

Study on the characteristics of impact load of wedge during water entry based on a fully nonlinear boundary element method

作　　者：王强 焦甲龙 WANG Qiang;JIAO Jialong(Shanxi Institute of Energy,Jinzhong 030600,China;South China University of Technology,Guangzhou 510641,China)

机构地区：[1]山西能源学院,山西晋中030600 [2]华南理工大学,广州510006

出　　处：《兵器装备工程学报》2024年第6期26-33,共8页Journal of Ordnance Equipment Engineering

基　　金：国家自然科学基金项目(52271316);山西能源学院院级科研基金项目(ZY-2023025)。

摘　　要：在兵器入水、飞行器迫降水面等结构物入水冲击问题属于强非线性流固耦合问题,计算时网格的划分重构、数值稳定与传递,以及射流根部的数值准确求解,通常制约着计算模拟的成败。本文中建立了一套满足全非线性边界条件的冲击载荷理论预报方法,通过引入拓展坐标系,有效解决了非线性自由液面上网格重构和数值传递的问题;通过引入辅助函数解耦了时域下的运动方程,准确求解了每个时间步下楔形体的速度、加速度和冲击压力,以二维楔形体为研究对象,通过开展落体试验验证了本理论方法的有效性。研究结果表明:流体重力对冲击压力具有显著影响,45°底升角楔形体的入水冲击压力主要分布在1.6倍入水深度的半宽区域内,压力峰值和次峰值一般发生在楔形体的尖端和射流根部;楔形体的冲击压力对较小底升角极为敏感,定量描述了二者之间的非线性关系;壁面效应与入水初速度无显著相关性,但底升角越小壁面效应越显著,45°底升角楔形体入水深度小于水域深度的1/3时,壁面效应尤其明显。研究结果为冲击载荷的理论研究和工程应用提供了参考。The problem of water entry impact of structures such as water entry of weapons and aircraft landing water surface is a strong nonlinear fluid-solid coupling problem.The division and reconstruction of grids,numerical stability and transmission,and the accurate solution of the jet root in the calculation usually restrict the success or failure of the calculation simulation.A boundary element method that fully satisfies nonlinear boundary conditions were established in this paper,which were used to predict impact loads more accurately.By introducing a stretched coordinate system,the problems of grid reconstruction and numerical transmission on the free liquid surface were solved effectively.By introducing an auxiliary function,the motion equation in the time domain is decoupled,and the velocity,acceleration and impact pressure of the wedge at each time step are accurately solved.The validity of this numerical method is verified by a free fall test of a two-dimensional wedge.The results show that the fluid gravity has a significant effect on the impact pressure.The water entry impact pressure of the wedge with 45°dead-rise angle is mainly distributed in the half-width area of 1.6 times the depth of water entry.The peak and sub-peak pressure generally occur at the tip of the wedge and the root of the jet.The impact pressure of the wedge is very sensitive to the smaller bottom angle.In this paper,the nonlinear relationship between the two is described quantitatively.There is no significant correlation between the wall effect and the initial velocity of water entry,but the smaller the dead-rise angle,the more significant the wall effect.When the water entry depth of the 45°dead-rise angle wedge is less than 1/3 of the water depth,the wall effect is particularly obvious.The research results provide a reference for theoretical research and engineering applications.

关 键 词：入水冲击 落体试验 边界元法 拓展坐标系 冲击压力 壁面效应 

分 类 号：O352[理学—流体力学] TJ630.1[理学—力学]