静水压力作用的水下结构振动及声辐射

采用有限元／边界元方法开发了静水压力作用的水下结构振动与声辐射的计算程序。依据不同分析域的特点，对结构域和流体内域采用有限元方法，对流体外域采用边界元方法。分析了流体一结构相似特性，使通过对常规结构有限元分析程序中的参数作合理设置，使之能直接用于内域流体声学有限元分析。流体外域采用边界元方法，选取合适的格林函数，能够考虑无穷远和自由液面边界条件。流体对结构的作用表现附加质量和附加阻尼。采用FORTRAN代码计算外域流体附加质量和附加阻尼矩阵，采用结构有限元分析程序对结构和内域流体作有限元分析，采用DMAP代码将附加质量和附加阻尼同结构质量矩阵和阻尼矩阵相叠加，实现了流固耦合计算。通过几何刚度矩阵对结构刚度矩阵修正来考虑静水压力对结构声辐射的影响。

Vibration and Radiation from Underwater Structure Considering the Effect of Static Water Preload

Based on finite element method/boundary element method, a program is developed for computing the radiation from underwater structures, which can consider the effect of static water preload. Different solution methods are used in different analysis fields. Finite element method is used in the structural and interior fluid field. Structural analogies for the acoustic field problems are used to build the finite element model. The analogies show that common finite element analysis program can be used for acoustic analysis directly by appropriately setting some parameters in the code. Boundary element method is used in the exterior fluid field. The radiation condition and the free water surface condition can be satisfied automatically by appropriately selecting Green furntion. The dynamic effects of exterior fluid act as added mass and added damping of the structure. FORTRAN codes are used to compute the added mass and added damping matrices. NASTRAN, a finite element analysis program, is used to carry out finite element analysis on the structure and interior fluid field. DMAP codes are used to modify the NASTRAN module, so as to coupl the exterior fluid field. To consider the effect of static water, differential stiffness matrix produced by NASTRAN is used to modify the stiffness matrix of the structure.