加纵肋平底圆柱壳振动和声辐射的FEM/BEM研究

建立了两端带平底板的加纵肋圆柱壳水中声辐射计算的FEM／BEM三维模型，探究了加肋的高度、宽度、数目对平底圆柱壳表面平均速度、辐射功率、辐射效率、声场指向性的影响规律。计算方法是在有限元软件ANSYS中做加肋平底圆柱壳建模、模态分析基础上，将有关数据（网格、模态）导入边界元软件SYSNOISE中计算流体-结构耦合状态下的辐射声场特性。结果表明：（1）纵肋的高度、宽度以及数目增大都可以引起平底圆柱壳的表面平均速度、辐射功率、辐射效率随频率变化曲线峰的移动，同时使声辐射效率增大，但使表面平均速度、辐射功率变化不明显。（2）纵肋的高度、宽度增大都使低频声辐射中两端平底板的贡献量增大，而使研究频域内的高频声辐射在激励力的反方向上增强。当径向激励力作用在纵肋上时适当调整均布纵肋的数目可以改变平底圆柱壳辐射声场的指向性。这对于水下结构辐射噪声预报以及噪声抑制具有重要意义。

On FEM/BEM for the Problems of Vibration and Acoustic Radiation from an Axially Stiffened Cylindrical Shell with Two End Plates

A 3-D model of finite element method/ boundary element method for computing the sound field radiated from an axially stiffened cylindrical shell with two end plates in water has been established, and the effects of the height, the width and the number of axial stiffeners on the mean surface velocity, the radiated sound power, the radiation efficiency and pressure directivity of sound field have been investigated. The meshing data and modal data of the model in vacuo obtained from FEM code ANSYS are put into BEM code SYSNOISE and used for computing the parameters of the coupled sound field. The results show that: (1)The increases in the height , the width or the number of stiffeners make the frequency curve peaks of the mean surface velocity, the radiated sound power and the radiation efficiency shift away from that of the cylindrical shell without stiffener, and makes the radiation efficiency increase. However it doesn't change the mean surface velocity and the radiated sound power apparently. (2) The increase in the height or the width of the stiffeners causes the contribution of low frequency acoustic radiation from two end plates to increase, and causes high frequency acoustic radiation to increase in the direction opposite to the driving force. The directivity pattern of the sound field can be changed by adjusting the number of axial stiffeners when the axially driving force is exerted on one of the stiffeners. All above is of significance to the prediction and control of noise radiated from underwater structure.