中文摘要：

在声固耦合的计算分析中，一般采用耦合的有限元或者耦合的有限元与边界元等数值方法来进行模拟。由于有限元系统偏硬，因而在使用有限元进行声学及声固耦合问题的模拟中，都会产生比较大的数值误差。为了降低声固耦合系统的刚度，降低有限元的计算误差，通过采用耦合的边光滑有限元法来对三维的声固耦合问题进行模拟。由于三角形网格和四面体对于任何复杂几何模型的离散适应性很强，因此在结构域中，将采用三角形来离散系统，而在声学域中，采用四面体来离散，并对结构域中三角形板单元以及流体域中的四面体单元都进行基于单元边的梯度光滑操作。通过数值算例的研究结果表明，光滑梯度操作能够适当降低有限元系统的刚度，使离散系统刚度更加接近连续系统的刚度，数值解更加接近真实解，从而为本方法的进一步应用打下基础。

英文摘要：

The coupled finite element method（coupled FEM） and coupled finite element method/boundary element method（coupled FEM/BEM） are always adopted to solve the structural-acoustic problems, and it is known that the finite element methods behave ＂over-stiffness＂ which induce the large numerical error for the structural-acoustic problems. In order to soften the ＂over-stiffness＂ and improve the results of FEM, a coupled ES-FEM model is extended to solve the structural-acoustic problems consisting of a plate structure interacting with the fluid medium. Three-node triangular elements and four-node tetrahedral elements are used to discretize the two-dimensional（2D） plate and three-dimensional（3D） fluid, respectively, as they can be generated easily and even automatically for complicated geometries. Numerical studies have verified that the gradient smoothing technique can provide a proper softening effect to the model, and hence significantly improve the accuracy of the solution for the coupled systems, which will lay the foundation for further applications.