When the fluid-structure coupled vibration of propellants and fuel tank in a launch rocket was analyzed, in order to achieve accurate modeling and efficient calculation, and provide modal parameters to the launch rocket system, the asymmetrically dynamic equations containing fluid node pressures and structure node displacements were deduced with the finite element method. Model reduction method was used to fluid node pressures, the symmetrically dynamic equations were obtained. Through solving a boundary value problem of equivalent Laplace equation the additional mass matrix, additional stiffness matrix and coupling terms being equivalent of fluid to structure in coupled dynamic equations were gained. The example of modal analysis for propellants and fuel tank demonstrated that this method can get modal frequencies of a fluid-structure coupled vibration system accurately and rapidly; this method makes abblication of efficient dynamics analysis of fluid-structure coupled vibration in engineering be possible, and provides a basis for changing a simple modeling of complex fluid-structure coupled vibration to an accurate 3-D one.%分析液体燃料运载火箭的推进剂及贮箱的耦合振动时,为了精确建模、工程化快速计算及为火箭整体系统提供液固耦合燃料系统等效模态参数,根据有限元方法得到包含液体节点压力和结构节点位移的非对称形式的耦合动力学方程组,将表征液体运动的节点压力缩聚到液体自由面,使得方程对称化.通过等价Laplace方程边值问题的求解,得到耦合动力学方程中液体对结构的附加质量矩阵、附加刚度矩阵及耦合项.简易贮箱液固耦合模态分析的算例结果表明,该分析方法能够精确、快速地获得液固耦合系统的模态频率等动力学特性.从而使得高效率的液固耦合动力学分析在工程上应用成为可能,并为运载火箭等复杂液固耦合结构的有限元建模由简化模型向三维精确模型建立和工程化应用建立了基础.
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