一维弹性结构在理想流体中的模态特性研究

为研究一维弹性结构在理想流体中的模态特性,建立了流固耦合振动模型。基于流体无旋、无粘不可压缩的假设,求解流体域内的速度势,根据流场分析得到水压力,将脉动水压力加载在结构表面,得到结构在水中的振动方程,并利用瑞利-利兹法求解得到圆柱梁在水中振动的固有频率和振型。在此基础上,基于应变测试对水池中的悬臂梁结构进行了模态识别,实验结果与计算结果相当吻合。研究发现,由于附连水质量的影响,弹性结构在水中的固有频率低于其在空气中的,其振型与空气中的形状基本一致,但其节点会向自由端偏移。

Modal Investigations of One-dimensional Elastic Beams in Ideal Fluids

In order to investigate the modal characteristics of elastic beams in ideal fluid, a coupled vibrational model is puted out. Based on the assumption that fluids are irrotational, inviscid and incompressible, the velocity potential of fluid domain is obtained. Pressure on the interaction area is acquired and is exerted on the structure, which leads to the governing equation for Fluid-Structure vibration. And on using Rayleigh-Ritz method, its natural frequency and mode shapes is obtained. An simplified test on a elastic beam submerged in Fluids is also carried out base on strain test. And the results matches well with those from computation. It is seen from the comparison that the nature frequencies under water is lower than those in air, while the modal shape is almost the same, except that the nodes will switch towards the free end of the beam due to the influence of added mass of water.