Theoretical Model and Numerical Simulation of Vortex Induced Flexible Tube Vibration
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摘要: 针对弹性管的涡致振动问题，分别在双向流固耦合模拟得到的流体力系数以及尾流振子模型的基础上，采用Euler-Bernoulli梁模型模拟弹性管，得到了弹性管涡致振动的运动方程，提出两种预测弹性管涡致振动的理论模型.首先通过4阶Galerkin方法离散系统的运动方程，采用由双向流固耦合数值模拟得出的流体力数据，预测了弹性管在横向流体作用下的振动响应；其次，引入尾流振子模型模拟弹性管与漩涡脱落间的耦合作用，并将预测结果与流固耦合模拟结果进行了对比分析.结果显示，采用谐和形式流体力的理论模型预测得到的结果偏小，而尾流振子模型能较好地模拟弹性管的涡致振动特性，预测结果比得上双向流固耦合得到的结果，说明尾流振子模型用于弹性管的漩涡脱落诱发振动是可行的和合理的.Abstract: In order to predict vortex induced vibration (VIV) of flexible tubes, the flexible tube was modeled as an Euler-Bernoulli type beam and the equations of motion for the tube under VIV were derived based on the fluid force coefficients obtained through fluid-structure interaction simulation and the wake oscillator model respectively. Two theoretical models for predicting VIV of the flexible tube were presented. Firstly, the infinite-dimensional model was discretized with the 4-order Galerkin technique. The tube vibration responses induced by cross flow was predicted successfully with the fluid force coefficients obtained through fully fluid-structure coupling simulation. Then, the results predicted by the wake oscillator model were compared with those by the fluid-structure interaction simulation. The research shows that, the vibration amplitudes predicted by the harmonic fluid force model is smaller than that predicted by the fluid-structure interaction simulation. However, the wake oscillator model properly simulates the vortex induced vibration characteristics of the tube, which agrees well with the fluid-structure interaction numerical results. That indicates the wake oscillator model is a feasible way to predict the vortex induced flexible tube vibration.
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