改进的湿模态法在流固耦合中的应用

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振动与冲击 ›› 2017, Vol. 36 ›› Issue (22) : 199-204.

论文

改进的湿模态法在流固耦合中的应用

刘瑞骏，郝志勇，郑旭，谈江林

作者信息 +

The application of improved wet mode method in the fluid-structure interaction

LIU Rui-jun, HAO Zhi-yong, ZHENG Xu, TAN Jiang-lin

Author information +

文章历史 +

摘要

针对流固耦合运动方程，指出了流体刚度矩阵的奇异性将导致现有的湿模态法无法直接使用，并指出了在湿模态法中使用分离零频项的方法存在的矛盾。文章说明了湿模态法的问题根源在于为了简化计算而提出的不合理的前提假设，即同时忽略流体的可压缩性及自由液面波动的影响。据此，提出了直接求解法和不动点法两种解决方法。前者适合流体规模较小的计算，而后者更适合大规模流体的耦合计算。应用不动点法，编制了Matlab程序，对某油底壳在不同盛油状态时的结构特性进行了仿真计算，对比表明随着盛油量从0逐步增加，结构模态频率呈先减小后增大的趋势并趋于平缓。加入流体后，结构模态的振幅大幅下降。除了第1阶模态，流体较少时的湿模态振型与干模态振型区别较大，但随着流体的增加，振型逐渐趋于稳定，与干模态振型接近。

Abstract

The singularity of the fluid stiffness matrix in the equations of motion was pointed out, which made the existing wet mode method unavailable. Meanwhile, the contradiction of the method that isolating the zero-frequency item was indicated. The paper shows that the root of the problem of the wet mode method is the unreasonable presumption that simultaneously neglects the compressibility of the fluid as well as the influence of the free surface fluctuation which aims at the easier computation. Two solutions called the direct method and the fixed point method are put forward based on the above conclusion. The direct method is more suitable for the computation with a small fluid domain scale while the fixed point method is fit for a large one. In this paper, the structural characteristics of an oil pan with different oil mass were calculated by a Matlab program based on the fixed point method. The comparison demonstrates that the structural modal frequencies decrease firstly, then increase and finally become flat with the oil mass increased increasing from 0. The deformation magnitude of the modal shapes decrease considerably when the fluid is added. For the same order of mode, the wet modal shapes differ a lot from the dry modal shapes with less fluid addition except the 1st mode. But the wet modal shapes tend to be stable and the same as the dry modal shapes with the continuous increase of the oil mass.

导出引用

刘瑞骏，郝志勇，郑旭，谈江林. 改进的湿模态法在流固耦合中的应用[J]. 振动与冲击, 2017, 36(22): 199-204

LIU Rui-jun, HAO Zhi-yong, ZHENG Xu, TAN Jiang-lin. The application of improved wet mode method in the fluid-structure interaction[J]. Journal of Vibration and Shock, 2017, 36(22): 199-204

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