五圆柱体结构群绕流特性及互扰效应研究

基于Fluent流体计算平台,运用大涡模拟方法对亚临界雷诺数Re=3900下“X”形排列五圆柱体结构群三维绕流特性进行研究,主要分析来流攻角α与间距比L/D两个关键参数对五圆柱体结构群的尾流区三维涡结构演化与流体力系数的影响,并揭示其内在流动互扰机理。研究表明:来流攻角和间距比的变化对五圆柱体结构群流动控制及互扰效应的影响显著。在小间距比工况下,观察到柱体群间隙区域内流体高速流动的现象,导致五圆柱体之间的互扰作用十分强烈。间隙流对中间圆柱体和下游圆柱体有较强的冲击作用,对其表面的流体力分布特性有显著的影响。另外,大间距比工况下,当α=0°与L/D≥5.0工况时,柱体群尾流效应强于其间隙流效应。当α=22.5°与L/D=7.0时,位于下游与中间处的圆柱体流体绕流特性存在较大差异。而当α=45°与L/D≥6.0时,位于上游与中间处的圆柱体尾流区均会产生正负交替的漩涡结构。

Study on the characteristics and interference effect of flow around five circular cylinders

Based on the Fluent fluid computing platform,the flow past five X-arranged circular cylinders has been investigated at Re=3900 by using the Large Eddy Simulation(LES)method.The effects of incidence angle(α)and spacing ratio(L/D)on the fluid force coefficients and vortex structures of five X-arranged circular cylinders in the wake are analyzed,while the interference mechanisms of flow around the cylinders are clarified.The study shows that the incidence angle and spacing ratio have a significant impact on the flow control and interference effects of the flow around five X-arranged cylinders.The high-velocity flow in the gap can be observed at small spacing ratios.And the flow interference among the cylinders is strong and complicated.The gap flow has a strong impact on the middle cylinder and the downstream ones,which gives rise to the change of the pressure distribution on the surface of the cylinders.Moreover,in the case of large spacing ratio,the wake effect is stronger than the gap flow one,whenα=0°and L/D≥5.0.However,for the case ofα=22.5°and L/D=7.0,the fluid flow characteristics on both sides are different between the downstream cylinder and the middle one.In addition,asα=45°and L/D=5.0,there is no vortex shedding in the wake region of the upstream cylinder,while there is the vortex street behind the middle one.In the case of L/D≥6.0,the positive and negative vortex structures are formed in the wake of the upstream and middle cylinders.