近水面状态有限长圆柱壳振动特性分析

Frequency analysis of submerged cylindrical shell near the free surface

基于波传播方法和镜像法,建立了近水面状态圆柱壳-声场耦合模型,并采用数值方法求解耦合系统的特征方程,得到了近水面状态圆柱壳的模态频率。理论分析结果与现有实验测量结果及有限元仿真结果的良好吻合验证了本文理论方法的有效性。数值分析表明:自由液面的存在使得水下圆柱壳结构的模态频率较对应模态下理想全浸没状态结构的模态频率明显增大;随着潜深的增加,自由液面对水下圆柱壳模态频率的影响逐渐减小,当潜深大于4倍壳体半径时,自由液面的影响可以忽略。

The sound-structure coupling model of a submerged cylindrical shell near the free surface is established based on the wave propagation approach and the image method. The effect of fluid free surface is also considered. The modal frequencies of the submerged cylindrical shell are obtained by solving the dispersion equation of the coupling system according to numerical approach. By comparing the modal frequencies from theoretical analysis with those from experiment work and numerical simu- lation analysis, it is found that the approach proposed in this work is effective and accurate. Some conclusions are also made from numerical analysis. The consideration of free surface will increase the modal frequencies of immersed shell compared with those of immersed shell ignoring the effect of free surface. However, the influence of free surface on shell modal frequencies will decrease as the immersion depth increases.