串列双旋转圆柱群绕流特性及互扰效应研究

Flow characteristics and interaction effect of tandem double-rotating cylinders

本文基于Fluent计算软件,对Re=200条件下,串列双旋转圆柱三维绕流问题进行数值模拟研究。探究不同间距比(L/D=1.5-5.0)和旋转速率(α=0.0-4.0)对旋转圆柱流体力系数、表面压力系数、流场特性以及涡脱落的影响。研究表明:流向涡主要由下游圆柱产生,当旋转速率较小(α<2)时为大涡结构,当α≥2时则转变为混合交错排列的小尺度结构;展向涡则主要由上游圆柱产生将下游圆柱包裹在内;圆柱旋转会导致尾流呈现不对称模态,尾涡向下侧发生偏移,随着转速的增加,圆柱表面以负压为主,吸力会增大从而抑制尾流的产生;随着α增大,上、下游圆柱阻力系数平均值变化规律相反,而升力系数均方根值变化规律相同;旋转速率对上游圆柱的阻力系数成分的影响较大,导致阻力系数平均值发生异号;仅在小间距比工况下下游圆柱阻力系数平均值会发生异号;当旋转速率较大时,上、下游圆柱的斯托罗哈尔数均会趋于0,随L/D增大其变化速度会加快。

Based on the Fluent calculation software,a numerical simulation study of the three-dimensional flow around a tandem double-rotating cylinder under the condition of Re=200 was carried out.The effects of different space ratios(L/D=1.5-5.0)and rotation rates(α=0.0-4.0)on the fluid force coefficient,surface pres-sure coefficient,flow field characteristics and vortex shedding of a rotating cylinder were explored.The study shows that the streamwise vorticity is mainly generated by the downstream cylinder.When the rotation rate is small(α<2),the streamwise vorticity is a large vortex structure,and whenα≥2,it transforms into a mixed and staggered small-scale structure.The spanwise vorticity is mainly generated by the upstream cylinder and wraps the downstream cylinder.The rotation of the cylinder will cause the wake to assume an asymmetrical mode,and the wake vortex will deviate to the lower side.With the increase of the rotation speed,the cylinder surface is mainly of negative pressure,and the suction force will increase to suppress the generation of the wake.With the increase ofα,the change law of the average value of the drag coefficients of the upstream and downstream cylinders is opposite,while the change law of the root mean square value of the lift coefficient is the same.At the same time,the rotation rate has a greater influence on the drag coefficient component of the upstream cylinder,resulting in a different sign on the average value of the drag coefficient.However,the aver-age value of the drag coefficients of the downstream cylinder will be different only under the working condi-tion of a small spacing ratio.In addition,when the rotation rate is large,the Strouhal numbers of the upstream and downstream cylinders will both tend to 0,and the change speed will increase with the increase of L/D.