非连续边界单元可以有效提高边界元法在具有复杂边界形状的实际问题上的应用能力。本文发展基于Burton-Miller法的无奇异二维声学非连续边界元法,通过带有解析解数值算例,对比不同类型单元的计算精度以得到最有效的单元类型,并考察非连续线性和二次单元的优化节点位置。同时本文采用伴随变量法进行声学敏感度计算,并结合MMA算法(The method of moving asymptotes)对Y型声屏障进行结构优化分析。
This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave problems.The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only.Moreover,a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived,and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating,translating and saving the multipole/local expansion coefficients of the image domain.The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems.As for exterior acoustic problems,the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method.Details on the implementation of the present method are described,and numerical examples are given to demonstrate its accuracy and efficiency.
