Acoustic disturbances and the resulting structural vibration is a very significant problem in aerospace engineering. The magnitude of the acoustic loads transmitted to the payload is a function of the external acoustic environment as well as the design of the spacecraft structure and its sound absorbing treatments. The high intensity acoustic fields produced during a launch of a Space Shuttle or an Expendable Launch Vehicle (ELV) can easily damage a spacecraft's mission critical flight hardware, such as its avionics, antennas, solar panels and optical instruments. The loads transmitted to the spacecraft structure from the launch vehicle (LV) in the first few minutes of flight are far more severe than any load that a payload experiences on orbit. The severity of the environment affects the design for withstanding higher launch loads, hence the cost of placing the payload into orbit. With such motivation and following earlier work, structural-acoustic interaction is modeled and analyzed using boundary and finite element coupling. The analysis is founded on the idealization of the problem into three parts; the calculation of the acoustic radiation from the vibrating structure, the finite element fonvulation of structural dynamic problem, and the calculation of the acousto-elasto-mechanic fluid-structure coupling using coupled BEM/FEM techniques. The computational scheme developed for the calculation of the acoustic radiation as well as the structural dynamic response of the structure using coupled BEM/FEM has given satisfactory results for acoustic disturbance in the low frequency range, which was the range of particular interest in many practical applications. However, for larger frequency range, it is well known that while the solution to the original boundary value problem in the exterior domain to the boundary is perfectly unique for all wave numbers, this is not the case for the numerical treatment of integral equation formulation, which breaks down at certain frequencies known as irregular frequencies or fictitious frequencies. Although such phenomenon is completely nonphysical since there are no discrete eigenvalues for the exterior problems, a method known as CHIEF (Combined Helmholtz Interior integral Equation Formulation) can be utilized to overcome such problem. Applications of CHIEF method to spherical shell geometry has given excellent results.
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