深水张力腿平台非线性涡激特性及水动力性能研究

平台涡激运动易导致立管及系泊系统疲劳损伤,危害其安全稳定性。该文引入雷诺平均法求解NS方程结合DES湍流模型对不同流速下深水张力腿平台三维涡激运动及流场特性进行了数值研究。采用GAMBIT软件建立计算网格,将求解动力学控制方程的代码嵌入UDF求解器中,采用动网格技术实现流场更新并求得作用于平台立柱和浮箱上的瞬时升力和拖曳力。采用最大值统计法和均方根统计法进行数据统计。研究发现:张力腿平台涡激运动流向振幅的大小随着约化速度的增大而增大,但在小范围内波动;横向振幅曲线最大值出现在0°来流、约化速度U~*=8.0处,大小为0.38D;三种来流工况流向平衡位置随无因次速度的增大而增大,但增长速度有所区别,22.5°和45°下流向平衡位置的增加速度要明显大于0°来流;22.5°来流升力系数谱能量较为分散,立柱及浮箱之间的干扰具有强非线性效应;最后对张力腿平台表面压力系数分布及涡量等值面特性进行了分析和探讨。

Study on the nonlinear characteristics of vortex induced motion and hydrodynamic performance of deepwater TLP

Vortex-induced motions of platforms are associated with rise and mooring system’s fatigue dam-age, which also endanger its security and stability. This paper studies the 3D vortex-induced motion and the flow field characteristics of deepwater TLP under different current velocities based on RANS (Reynolds-Av-eraged Navier-Stokes) solver for N-S equation combing with DES (Detached eddy simulation) turbulence model. Computational grid was set up by GAMBIT software and the code of solving dynamic control equa-tions was embedded to UDF (User Defined Function). The instantaneous drag and lift forces of the columns and pontoons can be solved after the flow field renewal is achieved by dynamic mesh technology. The maxi-mum statistical method and nominal statistical method were used to analysis the simulation results. The results indicate that the maximum stream-wise amplitude of TLP increase with the increase of reduced ve-locity, but it fluctuates on a small scale. The maximum transverse amplitude happen at the reduced veloci-ty of 8.0 from 0 degree current, and the value is 0.38D. The stream-wise equilibrium position of three dif-ferent flow approach angles increase with the increase of reduced velocity, but the growth rate is different. The growth rate of 22.5 degrees current and 45 degrees current cases is lager than the 0 degree current case. Spectrum energy of lift coefficient is relatively decentralized and the interference between column and pontoon has nonlinear effect. Finally, the pressure coefficient distribution and vorticity iso-surface charac-teristics of TLP surface are discussed.