双层壳体的船舶动力舱振动与声辐射的有限元结合边界元数值计算

利用ANSYS有限元软件，建立了双层壳体的船舶动力舱的水下结构流体耦合的声振模型。采用有限元结合边界元的方法，数值计算并分析了耐压壳体和轻质外壳的厚度变化对动力机械振动传递、水下外壳振动以及辐射噪声的影响，计算结果表明，本文的方法对大型复杂结构的水下声振预估有借鉴价值。

Numerical Calculation of Vibro-acoustic Behavior of Simulated Ship Dynamic Cabin with Double-shell by FEM/BEM

Numerical prediction of the vibration transmission and noise radiation from the ship diesel engine via a resilient mounting system to the ship shell is a key problem in naval engineering. For a simulated ship engine room with a two stage mounting system and a double shell, the fluid structural coupled model is built by finite element (FE) software ANSYS. Effects of the shell thickness are numerically studied by finite element method together with boundary element method. First the node displacement and the vibration transfer function in the cabin are computed by ANSYS. Then the obtained structure node displacement of the outer shell is drawn out and used as the boundary condition of the acoustic model. The radiated acoustic power level is computed by SYSNOISE as well. The numerical results show that (1) on the whole, the increase of the shell thickness plays an important role in reducing vibration and radiated noise in this complex system; (2) variation of the thickness of the shell, even the outer shell, may move the locations of vibrating transfer function peaks; (3) for the shells with the same thickness, the numbers of the peak values of the vibration velocity and acoustic power are more than that of vibration transfer function ; and (4) increase of the thickness of the pressure shell can weaken the fluctuation of the vibration transfer function, while the effect of the outer shell thickness variation is not evident. These results are in agreement with the vibro acoustic theory and demonstrate the reliability of the methods. The method in this paper can be further applied to acoustic prediction of a real submarine under the present hardware and software computing capability.