并列双圆柱绕流的水动力特性研究

Hydrodynamic Characteristics of Viscous Flow Past Two Side-by-Side Cylinders

多柱体系统在石油开采逐渐向深海发展的过程中得到广泛的应用，由于波浪、流对多柱体的影响易导致其破坏。因此研究多柱体系统绕流具有重大价值。目前多不等直径多柱体绕流的研究还有待深入。本文利用Fluent模拟雷诺数Re=3900，G／D为0．1～2．5，d／D为0．5、1．0情况下并列双圆柱的绕流过程，并根据模拟结果分析G／D和d／D的变化对大、小柱体涡脱落形态、升力系数cr、阻力系数G和sf值的影响。结果表明，随着G／D变化，涡脱落形态会呈现出不同的形式，绕流参数值也随之发生变化。当0〈G／D≤0．2时，柱后只有一个涡脱落，为单一涡脱落区，升、阻力系数值存在突变，St值小于单柱S￡值；当0．2〈G／D≤0．5～1．0时，柱后出现交替的偏斜流，为偏斜流区，升、阻力系数随着G／D的增大而减小，S￡值在两个极值之间变化；当0．5～1．0〈G／D≤2．5时，柱后有成对的涡旋，为双旋涡脱落区，升阻力系数值趋于稳定，St值稳定在0．2左右。偏斜流区与双旋涡脱落区之间的临界间距比G／D随着d／D的增大而增大；不等直径情况下，间隙流偏斜对大柱的影响小于对小柱的影响。

Cylindrical marine structures （marine riser, subsea pipeline） have been widely applied on the deep ocean development. The multiple-pipelines can be more easily damaged because of its tight arrange- ment compared with the single cylinder, under the effect of wave and current flow. Therefore, more at- tention should be paid to the multi-pipelines. The flow field for two cylinders arranged in a side-by-side configuration with different G/D and d/D was simulated by using Fluent. The simulations included ca- ses with Re= 3 900, surface-to-surface gap between the large cylinder and the small cylinder from 0. 1D～2.5D, and the diameter ratio between the two cylinders of 0. 5 and 1.0. The vortex characteristics and hydrodynamic forces （lift coefficient, drag coefficient and St） were analyzed based on the simulation. The obtained results show that. （1）Single vortex shedding at small G/D from 0.1～ 0. 2, biased flow at intermediate G/D from 0. 2～ 0. 5 or 1.0, symmetric flow at large G/D from 0. 5 or 1.0～2.5. （2）At small G/D from 0. 1～0. 2, lift and drag coefficients change sharply and St is smaller than the single cyl- inder＇s St. At immediate G/D from 0.2～0.5 or 1.0, drag coefficients fluctuate, lift coefficients change sharply at the critical G/D and St changes between two extreme values. At large G/D from 0. 5 or 1.0～ 2. 5, lift and drag coefficients and St tends towards stability. （3）The critical G/D increases as the diD increases. With the condition of same G/D, the gap flow has smaller effect on the large cylinder as the d/D decreases. （4）d/D also has obvious effect on the forces coefficients and St.