尾流干涉下考虑流固耦合作用的海洋立管涡激振动的数值模拟

摘要

The vortex-induced vibration ( VIV) of two tandem risers with effects of wake interference is investigated in FLU-ENT, dynamic mesh technology and user-defined functions.The fluid-structure-interaction model is presented by solving the Navier-Stokes equations, the turbulence model of RNG and structural dynamic response equation.The distance between the two tandem risers was 4 times the diameter.The results show that the upstream and downstream risers both have vortex shedding;with effects of wake interference, considering fluid-structure interaction the lift coefficient of the downstream riser is bigger than the lift coefficient with the downstream riser fixed; the vibration of the downstream riser has the displacement's detuning; when approaching to'lock-in', the lift coefficient of the downstream riser has a phenomena of multi-frequency and one of the frequencies is close to the nature frequency.With reduced velocity increasing, the multi-frequency fades away;the amplitude of the lift coef-ficient of the downstream riser changes periodically, and wake zone of the downstream riser appears even'fault'.%利用Fluent软件，运用动网格技术及用户自定义接口编程，通过求解N－S方程、RNG湍流模型以及结构动力学模型实现流固耦合，对串联间距为4D的等径立管进行数值模拟，分析在尾流干涉下立管的涡激振动。基于数值模拟结果分析：串联间距为4D时上下游立管都有漩涡脱落；下游立管在尾流干涉下，考虑流固耦合时相比固定立管时所受升力增大，立管振动有“失谐”，涡激振动到达“锁定”状态以及之后的一段约化速度范围内，升力系数呈现多频现象，且有一个频率总是接近立管固有频率，随着约化速度增大，涡激振动远离“锁定”状态多频现象逐渐减弱，同时升力系数幅值周期性变化，下游立管剧烈振动使其自身尾流区出现“断层”。