带有凹陷的环肋圆柱壳水下声振特性分析

为研究凹陷对环肋圆柱壳水下振动与声辐射的影响,采用结构有限元耦合流体边界元方法,通过FOR TRAN代码计算流体附加质量和附加阻尼,用DMAP代码将附加质量和附加阻尼矩阵同结构质量和结构阻尼矩阵叠加,实现了流固耦合计算,得到了在不同凹陷范围、凹陷深度、凹陷位置,以及力作用点与凹陷的相对位置时,圆柱壳的水下均方法向速度级和辐射声功率级频响曲线。分析结果表明:当力的作用点不在凹陷位置时,凹陷对圆柱壳的水下振动与辐射噪声影响很小,可以忽略;当力的作用点在凹陷位置时,带有凹陷的圆柱壳水下均方法向速度级和辐射声功率级的分贝值明显高于无凹陷时的情形,曲线峰值相差达4 dB。因此,在对带有凹陷的环肋圆柱壳进行试验研究时,应尽量避免激励力作用在凹陷位置,这样得到的结果会更准确。

Vibration and Acoustic Radiation of Cylindrical Shell with Indentation

To investigate the effects produced by a stiffened cylindrical shell indentation on underwater vibration and acoustic radiation, an approach combining the finite element and boundary element was adopted. Through FORTRAN and DMAP codes, the added mass and added damping matrices were first computed, and then added to the structural mass and damping matrices, where the problem of fluid-structural interaction was solved. The corresponding frequency response curve measuring the mean-square velocity and radiated sound power from cylindrical shells with different sizes, depths, positions of indentation were obtained. The results show that when the force point deviates from the position of indentation, the indentation has little influence on underwater vibration and acoustic radiation. On the other hand, when the force point locates at the same position as the indentation, the decibels of mean-square velocity and radiated sound power appear to be significantly higher （up to 4 dB） than that those under the condition without indentations. Therefore, it is advisable to avert forces from positions of indentation when conducting experiments on vibration and sound radiation from cylindrical shells.