新型深吃水多立柱FDPSO变截面立柱涡激运动特性研究（英文）

Study on Vortex-induced Motion Characteristics of Variable Cross Section Multi-column of a New Type of Deep Draft FDPSO

文章采用FLUENT软件结合分离涡法对某新型深吃水多立柱FDPSO变截面立柱涡激运动特性开展了研究。将变截面立柱涡激振动系统简化为质量-弹簧-阻尼模型,引入雷诺平均应力模型求解不可压缩粘性Navier-Stokes方程,通过计算出流场作用于柱体的瞬时升力与阻力,并基于UDF程序求解运动微分方程同时运用动网格技术实现流场更新,实现了对变截面立柱涡激运动的数值模拟。对不同来流速度下变截面柱绕流和涡激运动特性进行了研究,分析了变截面柱阻力系数、升力系数、运动幅值和运动轨迹等,研究发现：在高雷诺数单柱绕流模拟中采用三维数值模型更具优势,变截面柱后方同一时间内可能有多个旋涡产生,旋涡之间相互影响,抑制了旋涡对柱体的升阻力作用;在折合速度6~9范围内,变截面柱未出现明显“锁定”现象;变截面柱涡激运动的横荡振幅峰值在U_r=4.5,约为1.2D;变截面柱流向平衡位置随着折合速度增加而增加;变截面柱运动轨迹出现了典型的“8”字形,但变截面柱的轨迹相对较紊乱。

The software Fluent combined with detached eddy simulation （DES） is used to study the characteristics of a FDPSO variable section column vortex-induced motion. The variable section column vortex-induced motion is simplified into a mass-spring-damp system. The numerical simulations are done by calculating the instantaneous lift and drag forces of column and applying Reynolds-Averaged solver for the Navier-Stokes equation, then dynamic mesh technique is applied to update the flow field while UDF program is used to solve the differential equation of motion. The characteristics of variable section column flow around and vortex-induced motions at different flow velocity are studied. Drag coefficient, lift coefficient, vortex-induced motion amplitude and trajectory are discussed, too. The results indicated that three dimensional numerical models are more advantaged in simulation of high Reynolds number flow around a single column, and there are multiple vortices interacting with each other in the rear of the variable section column, which restrains the lif t and drag effect of vortex on the column. When the reduced velocity ranges from 6 to 9, there is no obvious ＇ lock- in’ phenomenon. The transverse vibration amplitude ofvariable section column vortex-induced motions is about 1.2D at reduced velocity 4.5. The stream-wise equilibrium position increases with the increase of reduced velocity. The trajectory of variable section column is disordered and appears ＇ 8’ shape.