螺旋侧板对立管水动力影响的数值模拟研究

针对附有三板式螺旋侧板的立管水动力影响问题展开三维数值模拟研究，采用CFD大涡模拟方法，对不同的螺旋侧板高度h和螺距P在雷诺数分别为3 900，10 000和20 000条件下进行模拟分析，得到立管后方阻力系数CD、升力系数CrmsL、斯特劳哈尔数St及其频谱等特性。模拟结果表明:螺旋侧板对立管升力和阻力有明显的抑制效果，升力系数均方根值CrmsL较光滑立管降幅最大达到95.8%，但随着螺旋高度h的增加，会引起立管的阻力增加，螺旋高度h为0.1D～0.2D（D为立管直径）时的抑制效果较好，并且h为0.1D时的抑制效果最为理想；CD值和CrmsL值均随螺距P的增大而增大并保持在较低值范围，两者均在P=12.5D附近出现了随螺距P的增大而减小的现象，侧板螺距P在取值为5D～17.5D范围内的选择对立管的升力和阻力抑制效果较好。

Numerical simulation study on hydrodynamic effect of helical strakes to riser

The three-dimensional numerical simulation study on the hydrodynamic effect of riser with three-plate helical strakes was carried out. The simulation analysis was conducted under different heights h and pitch P of helical strakes with the Reynolds number of 3 900, 10 000 and 20 000 respectively by using the CFD Large Eddy Simulation (LES) method, and the characteristics of drag coefficient CD, lift coefficient CrmsL, Strouhal number St and its frequency spectrum behind the riser were obtained. The results showed that the helical strakes had an obvious inhibitory effect on the lift force and drag force of riser. The root mean square value of lift coefficient CrmsL had the maximum decreasing amplitude of 95.8% compared with the smooth riser, but with the increase of height h, the drag force of riser increased. The inhibitory effect was better when the height h was 0.1D - 0.2D, and the inhibitory effect was the best when the height h was 0.1D. Both the drag coefficient CD and the lift coefficient CrmsL increased with the increase of pitch P and kept in the range of lower values, but both of them decreased with the increase of pitch P when P was around 12.5D. The pitch P of helical strakes had better inhibitory effect on the lift force and drag force of riser when the pitch P was in the range of 5D - 17.5D.