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静水压力作用的水下结构振动及声辐射 总被引:5,自引:0,他引:5
采用有限元/边界元方法开发了静水压力作用的水下结构振动与声辐射的计算程序。依据不同分析域的特点,对结构域和流体内域采用有限元方法,对流体外域采用边界元方法。分析了流体一结构相似特性,使通过对常规结构有限元分析程序中的参数作合理设置,使之能直接用于内域流体声学有限元分析。流体外域采用边界元方法,选取合适的格林函数,能够考虑无穷远和自由液面边界条件。流体对结构的作用表现附加质量和附加阻尼。采用FORTRAN代码计算外域流体附加质量和附加阻尼矩阵,采用结构有限元分析程序对结构和内域流体作有限元分析,采用DMAP代码将附加质量和附加阻尼同结构质量矩阵和阻尼矩阵相叠加,实现了流固耦合计算。通过几何刚度矩阵对结构刚度矩阵修正来考虑静水压力对结构声辐射的影响。 相似文献
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讨论了海洋大体积结构的流固耦合分析数学模型,建立了不可压缩理想流体中流固耦合系统结构运动微分方程,给出了用干模态分析方法计算流体附加质量矩阵、流体阻尼阵和流体附加刚度矩阵以及广义力的计算公式. 相似文献
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基于完全耦合算法对绕二维NACA0009水翼流固耦合特性进行了数值模拟研究。采用Theodorsen模型和Munch模型对刚性和弹性水翼的水弹性响应进行了数值计算,分析了流体与结构的相互作用关系,研究了影响结构水弹性响应和流固耦合特性的因素。研究结果表明:考虑了流体黏性的Munch模型与基于势流理论的Theodorsen模型对气动弹性响应的数值计算结果基本一致,而Theodorsen模型由于没有考虑流体黏性在一定程度上低估了结构的水弹性响应。结构的惯性、阻尼和刚度力矩与流体的相应附加载荷均处于同一数量级,故流体与结构的相互作用不可忽略,尤其对于弹性水翼,流体的惯性、附加阻尼作用增大,流固耦合算法的数值稳定性对流固耦合特性的计算结果影响将更大。外部激励频率为非共振频率时,结构的刚度作用是影响水弹性响应的主要因素,外部激励频率为共振频率时,流体的附加阻尼和附加刚度作用减弱,除结构的刚度作用外,流体与结构的惯性作用对水弹性响应和流固耦合特性的影响也较大。 相似文献
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为研究凹陷对环肋圆柱壳水下振动与声辐射的影响,采用结构有限元耦合流体边界元方法,通过FOR TRAN代码计算流体附加质量和附加阻尼,用DMAP代码将附加质量和附加阻尼矩阵同结构质量和结构阻尼矩阵叠加,实现了流固耦合计算,得到了在不同凹陷范围、凹陷深度、凹陷位置,以及力作用点与凹陷的相对位置时,圆柱壳的水下均方法向速度级和辐射声功率级频响曲线。分析结果表明:当力的作用点不在凹陷位置时,凹陷对圆柱壳的水下振动与辐射噪声影响很小,可以忽略;当力的作用点在凹陷位置时,带有凹陷的圆柱壳水下均方法向速度级和辐射声功率级的分贝值明显高于无凹陷时的情形,曲线峰值相差达4 dB。因此,在对带有凹陷的环肋圆柱壳进行试验研究时,应尽量避免激励力作用在凹陷位置,这样得到的结果会更准确。 相似文献
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对有限元法离散流固耦合方程进行了简要的介绍,给出了粘性流体与弹性结构的全耦合模型。流体采用k-ε湍流模型进行了有限元计算,采用ALE描述实现固体Lagrangian描述到流体Eulerian描述的过渡,使大变形带来的流体域网格畸变得以避免。对流固耦合方程,采用流固全耦合的迭代算法进行了迭代求解,最后模拟了高雷诺数下湍流流动中冲击致使涡轮结构旋转的过程。计算结果表明,流固耦合的算法是可靠的。 相似文献
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空间复合材料加筋板流固耦合振动分析 总被引:6,自引:0,他引:6
本文用结构有限元与流体边界元方法研究了空间复合材料加筋板结构的流固耦合自由振动,推导了用于结构分析的分项插值型复合材料八节点板单元和三节点梁单元,以及用于流场分析的线性边界单元。用修正的RIRZ向量法与波前法相结合的方法求解特征值问题,避免了因附连水质量引起的结构质量矩阵为满阵的内存困难和非对称矩阵方程约化困难。算例表明,附连水质量对复合材料结构的动力特性影响要比各向同性材料严重得多。 相似文献
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The constant added mass (CAM) method and the fluid-structure interaction (FSI) method are widely used to simulate ship-ship and ship-ice collisions. In the CAM method, the hydrodynamic effect of the surrounding water is treated as a constant added mass, whereas in the FSI method the surrounding fluid flow is explicitly modelled. The objective of the paper is to compare the two methods and to explain the causes of the differences in the results. We considered collision between a freshwater ice mass and a floating steel structure. For both methods, the numerical simulations were performed with the LS-DYNA software. The behaviour of the ice mass was modelled using an elliptic yield criterion and a strain-based pressure-dependent failure criterion. To ensure realistic ice behaviour, the ice model was calibrated using general trends found in laboratory and in-situ indentation tests with focus on the laboratory-grown ice and the fluid model in the LS-DYNA was verified by comparing the added mass coefficients for a spherical body and a rectangular block with the corresponding WADAM results. To validate and benchmark the numerical simulations, experimental data on ice-structure interactions in water were used, including the acceleration of the floater wall measured with the dynamic motion unit (DMU), the relative velocity between the ice mass and the floater before the impact and some images extracted from video recording of the test. The comparisons indicated that the FSI method yields better results for the motion of the floater, i.e., the acceleration of the floater wall caused by the ice mass’s impact and the relative velocity were in reasonably good agreement with experimental measurements. It was also found that the CAM method was faster but predicted a higher peak contact force and more dissipated energy in the ice mass than in the FSI method. 相似文献
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本文用流体边界元结合結构模态综合技术对大型结构的流固耦合问题的计算方法进行了研究。基于对用常数边界元计算附连水质量的物理意义的研究,并结合结构部分的计算,提出了一种假设的模态——拟湿模态。数值计算表明,本文的理论结果有足够的精度。 相似文献
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本文提出了流固耦合振动一种新的计算方法——组合模态综合法。该方法建立在流体-固体有限元组成的杂交子结构模型基础上.对流体子结构采用约束模态(静力变换模态),同固体子结构的两种模态——模综超元法中的动力变换模态和Craig的固定界面模态进行组合,以组合模态作为广义坐标对流固杂交子结构的运动方程进行变换获得两种形式的计算方法。本方法中采用了先装配流体子结构后装配固体子结构的技巧,从而消除了流体元的全部自由度和固体子结构的全部内自由度,仅保留固体子结构对接边界自由度,使最后计算特征值的矩阵阶数保持与结构中的模态综合超单元法及Craig法的阶数完全相同,大大减少了计算机时。 通过曲弯曲板元和平面膜元的组合板元构成的立体方盒结构以及三维矩形有限元的流固耦合振动计算,获得了与P.C.Chowdhury用整体有限元计算及光测实验一致的数值结果。 相似文献
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水-结构的耦合振动是一个比较复杂的问题,在设计中,只有考虑水体对结构基频及阻尼比等振动特性的影响,才能使结构设计更为合理、可靠。以往研究多分析水体的附加质量效应对桩柱基频的影响,对水深、桩径、上部结构等因素的影响尚缺乏进一步的研究,对水体的阻尼比增大效应也缺乏定量分析。鉴于工程的需要,利用有限元分析软件ADINA建立水体-桩基结构相互作用的三维有限元数值模型,对流固耦合作用下结构的基频和阻尼比进行计算,分析多种因素对水中结构振动特性的影响,并给出水体产生的阻尼比推荐值。结果表明,水体会引起结构基频降低及结构阻尼比增大,流固耦合作用对振动特性的影响不容忽视。 相似文献
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The added mass coefficient and the water level indexformulas for the same-phase and anti-phase vibration of rectangularliquid tanks' bulkheads were derived based on dry mode theory.Three fluid-structure interaction numerical methods including FluidFEM and Fluid BEM were used in this case. The comparison ofnumerical and theoretical results by the present method shows thatANSYS/FluidS0 is more credible, the NASTRAN/Virtual MassMethod is more suitable for engineering calculations and results ofthe same-phase vibration by the present method is more accurate. 相似文献
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In this paper, vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method (FEM) by 8-node acoustic fluid elements. Vibration characteristics of the structure in finite fluid domain are calculated combining structure FEM mass matrix. By writing the relevant programs, numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. 相似文献
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《船舶与海洋工程学报》2015,(3)
In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method(FEM) by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. 相似文献