环筋对水下平底圆柱壳的声振特性影响

本文建立了计算两端带平底板的有限长圆柱壳水中声辐射的FEM／BEM三维模型，探索了加筋的高度、宽度、数目对平底圆柱壳的辐射功率、辐射效率、法向声强、声场指向性的影响规律。计算方法是在有限元软件ANSYS中做加筋平底圆柱壳建模、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）随着环筋高度、宽度增大，激励点声压峰和法向声强峰在0-400Hz频率范围内数目减少且峰向高频方向移动，同时辐射声功率在减小（除个别模态峰值外），而辐射效率随筋高增大而增大。（2）环筋数目的增加使激励点辐射声压和法向声强峰数目明显减少，使辐射声功率明显低于无筋圆柱壳的辐射声功率，辐射效率随环筋数目增大而增大。（3）环筋宽度变化对声场指向性影响不大；圆柱壳声场指向性随环筋高度和数目增加出现较大变化，尤其是在研究的频段内的f=51Hz和f=301Hz上。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。

Effect of ring stiffeners on the vibration of and sound field radiated by a cylindrical shell with two end plates

A 3-D model of finite element method/boundary element method for com- puting the sound field radiated by a finite long cylindrical shell with two end plates in water is established,and the effects of the height,the width and the number of the ring stiffeners on the radiated sound power,radiation efficiency,normal sound intensity and pressure directivity of the radiated sound field are 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 are:(1)Pressure peaks and normal sound intensity peaks at the driven point will shift to higher frequency and the peak numbers will decrease when the width or the height of the ring stiffeners increases.Moreover the radiated sound power except some modal peaks will decrease while the radiation efficiency will increase with the increase in the width or the height of the ring stiffeners.(2)The increase in the number of ring stiffeners makes both the number of pressure peaks and the normal sound intensity peaks at the driven point decrease abruptly,makes the radiated sound power lower than that of the cylindrical shell without stiffeners,and also makes the radiation efficiency increase. (3)Increases in the number and the height of ring stiffeners make the directivity pattern very different from that of the cyhndrical shell without stiffeners,especially at frequency 51Hz and 301Hz,but the change of their width has little effect on the directivity.All above are of significance to the prediction and control of noise from underwater structure.