不同工况下有限长圆柱绕流实验测量及分析

Experiments and numerical simulations of the three-dimensional flow around a finite-length circular cylinder

为了研究不同工况对有限长圆柱绕流升阻力系数及尾流场的影响规律,采用CFD与实验相结合的方法,对三维有限长圆柱在不同长径比和雷诺数工况下的流动进行了模拟和实验验证。结果表明,在长径比AR≤3时,有限长圆柱的阻力系数几乎不受长径比的影响,但随雷诺数的增加有一个逐渐减小的趋势。对流场的分析发现,圆柱自由端的存在使流动具有更明显的三维特性,自由端的"下洗"作用会绕过自由端冲击圆柱后方的漩涡脱落,导致阻力系数小于无限长圆柱。在长径比AR≥6时,漩涡在圆柱的中下部周期性出现,并且几乎与圆柱平行;在圆柱的中上部,呈现出一定的角度。本文研究结果可为海工结构设计提供一定的数据参考。

In order to study the influence of different working conditions on the drag coefficient and wake field around a finite-length cylinder,CFD and experiments were used to simulate and verify the flow of a three-dimensional finite-length cylinder under different aspect ratio and Re number conditions in this paper.Both results show that,when the critical aspect ratio is over 3,the drag coefficient of a finite-length cylinder remains basically stable under these conditions and almost independent of the aspect ratio.But it tends to decrease with the increase of Reynolds number.Numerical analysis of the flow field reveals that the existence of the free end of the cylinder makes the flow have a more obvious three-dimensional characteristic.The"downwash"will bypass the free end impacting the vortex behind the cylinder,resulting in the drag coefficient less than that of an infinite cylinder.When the aspect ratio AR≥6,the vortex appears periodically in the middle and lower part of the cylinder and is almost parallel to the cylinder.;in the middle and upper part of the cylinder,it presents a certain angle.The above results can provide a richer data reference for the design of related offshore structures.