水中薄板振动和辐射声场特性

Characteristics of vibration and sound field radiated by a thin cracked plate in water

为了探究裂纹薄板在水中的振动和辐射特征,提出了一种置于无限大障板上的裂纹薄板水中振动频率以及辐射效率的简便计算方法。在假定薄板小振幅振动、水中模态挠度近似为真空模态挠度的条件下,利用瑞利积分得到了因流体压而引起的附加质量密度;进而应用瑞利方法得到了薄板水中振动频率与真空中振动频率、量纲一附加虚质量增量之间的关系;在真空中模态的有限元方法计算所得数据以及采用适当方法处理奇点积分的基础上,应用离散积分计算了量纲一附加虚质量增量的值;从真空中模态特征频率出发用迭代法计算,直到水中频率收敛为止,得到水中薄板的特征频率,并计算了薄板的模态辐射效率。

In order to investigate the characteristics of the vibration and radiation of a thin cracked plate in water, a simple computational method for the vibration frequencies of a thin clamped baffled plate with an artificial crack in water is described. Under the conditions that the plate vibrates in small amplitude and the modal deflection in water equals that in vacuo, the added mass density due to the water pressure is expressed using Rayleigh＇s integral. Then the relationship among vibration frequency of the plate in water and that in vacuo and the nondimensionalized added virtual mass incremental（NAVMI） is obtain by utilizing Rayleigh method. Based upon the data of modal analysis for the plate in vacuo by finite element method（FEM） and properly dealing with the integral at singular dot, the value of NAVMI is obtained by discretizing the integral. Moreo vet the vibration frequencies of the plate is computed using iterative method, which begins with the in vacuo eigenfrequency and continues until in-water eigenfrequency converges. The present approach is validated by comparison the NAVMI computed here with the results of fathers. 9 tabs, 2 figs, 17 refs.