ANALYSIS ON 2D CRACKED STRUCTURE-ACOUSTIC COUPLING PROBLEMS
二维含裂纹结构与声耦合问题研究

The effective control of noise and vibration in a structural acoustic system depends largely on the accurate evaluation of the sound-structure interaction which is characterized by the energy transferring back and forth between the acoustic field and the structure. When the fluid is heavy enough, both of the responses of the sound field and the structure can be significantly affected by this sound-structure interaction. Applications of interest include acoustic radiation and scattering from a submerged elastic structure, acoustic cavity analysis, and dynamics of fluid-filled elastic pipe systems. In this paper, the cracked 2D elastic structure sound interaction problems are studied by employing fractal two level finite element method combined with boundary element method. The cracked elastic structure is discretized by fractal two level finite element method, which is divided into two parts by an artificial boundary. The crack neighbouring domain is discretized by the fractal finite element method, which can reduced the freedom degrees greatly through transforming the nodal displacements to a set of generalized coordinates, the another domain is discretized by the conventional finite element method. The exterior acoustic field is calculated by boundary element method, which satisfies automatically Sommerfeld's radiation condition. In the numerical simulation procedure, the radiation and scattering acoustical pressure by an infinite long cracked aluminum cylinder immersed in fluid are calculated, the results show that the resonate frequencies of the structural-acoustic coupled system become lower with the depth of the crack increase, and that the effect on the acoustical field by the crack is particularly pronounced in vicinity of the crack tip.