水中平面冲击波对刚性方形台的绕射效应研究

Study on Diffraction Effects of Planar Underwater Shock Interaction with Rigid Quadrilateral Structure

采用LS-DYNA模拟了水中平面冲击波与刚性方形台的相互作用,分析得到方台正面和背面绕射波特性及其迹线。研究表明,水中冲击波的拐角绕射会在拐点处形成"涡流",在其邻近区域产生"零"压力场,从而出现"空化"效应,致使结构邻水面产生负压作用,这是结构产生破坏的一个重要成因。基于绕射效应模拟结果和水的高压状态方程导出的直方台背面绕射压力计算公式,适用于无自由水面影响且忽略水中结构变形时的绕射冲击波压力计算。这对结构背部绕射效应的理论分析具有指导作用。

Finite element simulation using LS-DYNA was performed to investigate the interaction of underwater planar shock wave and rigid quadrilateral structure. The characteristics of diffraction waves on both front and back surface of the rigid structure were analyzed and trace lines were gained. Vortex was formed near the corner of the structure diffracted by underwater shock with a void part of zero pressure existing in the local fluid region. Bulk cavitation near fluid-structure interface leads fluid pressure to drop to negative value, which is an important damage factor to merged structures. A derived pressure formulas of diffraction wave to rigid square structure is on the basis of simulation results and water＇s EOS. It is applicable to calculate diffraction pressure to underwater structure without affection of free water surface and deformation of the structure. It is helpful to the theoretical analysis of diffraction shock wave to underwater structure.