流体载荷对水下自由阻尼板阻尼损耗因子的影响

结构的阻尼损耗因子是潜艇降低水下辐射噪声的重要参数。为此，采用谱有限元法以计算流体载荷作用下的自由阻尼板的结构损耗因子，探讨辐射损耗因子同功率转换系数间的关系；然后使用谱有限元法比较了含流体和不含流体的自由阻尼板的结构损耗因子的差异，使用能量法对相关计算结果进行验证；最后使用三维模型对流体载荷作用下的自由阻尼板的功率转换系数进行了计算，进而分析功率转换系数同阻尼层杨氏模量、阻尼层厚度、阻尼层材料损耗因子等参数的关系。研究发现：在低于第二阶弯曲波产生频率的频段范围内，无流体时的损耗因子小于有流体的自由阻尼板；从频段平均的角度来看，功率转换系数在低频存在较大峰值，在高频变化较为平缓且数值较小；实际潜艇在流体载荷下主要通过改变结构的阻尼来改变其辐射的阻尼损耗因子。分析结果对于潜艇结构阻尼的优化设计有参考价值。

Influence of Fluid Loading on the Damping Loss Factor of Underwater Unconstrained Damping Plates

Spectral finite element method is developed for calculating the structural loss factor of an unconstrained damping plate with the fluid loading considered.The relationship between the radiation loss factor and power conversion coefficient is analyzed.Then,the structural loss factor of the unconstrained damping plate considering the fluid loading is compared with that of the plate without considering the fluid loading.The results are verified by using the energy method.Finally,the power conversion coefficient of the underwater unconstrained damping plate is calculated using threedimensional elastic model.Variation law of the power conversion coefficient with the variations of the Young＇s modulus,thickness and the material loss factor of the damping layer is discussed.The study shows that within the frequency band below the second- order bending wave＇s starting frequency,the structure loss factor of the unconstrained damping plate without fluid loading is less than that with fluid loading.From the perspective of the frequency average,the power conversion coefficient has large peaks in the low frequency range,and it varies gently and has small values in the highfrequency band.The radiation damping loss factor of the actual submarines under the fluid loading can be changed by changing the structure loss factor.Results of the study may have some reference values for the optimal design of structural damping for submarines.