张力腿平台绕流数值模拟分析

Numerical simulation of flow around a tension leg platform

在一定来流条件下,张力腿平台(tension leg platform,简称TLP)的立柱后缘出现周期性的交替旋涡脱落,致使立柱受到垂直于来流方向的升力和平行于来流方向的阻力作用,导致TLP产生大幅度往复运动,显著增加平台结构和系泊系统的负载。目前,关于单柱、多柱结构绕流问题的研究较多,但对于TLP绕流特性的研究较少,机理尚存不明确的地方。为研究TLP的绕流力变化情况和流场特征,开展了数值模拟分析。利用计算流体动力学数值模拟软件,基于雷诺平均(RANS)法和分离涡模拟(DES)法对TLP绕流场进行仿真分析,揭示了TLP的绕流特性。结果表明,在3种来流角度和多个折合速度V_(r)下,TLP绕流的流体力系数存在明显差异,升力系数时域曲线呈现脉动性。TLP的上、下游立柱间存在明显的相互作用,影响了旋涡的形成与发展。TLP的旋涡脱落大多集中在平台固有频率附近,且在V_(r)=7,来流角度为0°时,升力系数频谱峰值最大,旋涡脱落集中。

The columns of the TLP(tension leg platform)will have a periodic vortex shedding alternately under certain flow conditions,which makes the columns subject to the lift force perpendicular to the flow direction and the drag force along the flow direction.Flow causes a strong reciprocal displacement of the TLP,and increases the load on the hulls and mooring systems.Numerous researches have been conducted upon the flow around cylinders till now,however little attention has been paid to the characteristic of the TLP.Numerical simulations were carried out to study the force variations and wake characteristics of the TLP.Based on CFD numerical simulation software,the RANS and DES were selected to simulate the flow.The results show that there are significant differences in the fluid force coefficients of the TLP at three incoming flow angles and multiple reduced velocities.Time histories of the lift coefficients show pulsation.There are obvious interactions between the upstream and downstream columns of the TLP,which affect the formation and development of the vortex.Most of the vortex shedding of the TLP is concentrated near the natural frequency of the platform.When V_(r)=7 and the incoming flow angle is 0°,the number of peaks in the lift coefficient spectrum is the lowest and the vortex shedding is the most concentrated.