低雷诺数60°交叉双圆柱直接数值模拟研究

Direct numerical simulation of low Reynolds number 60 degrees intersecting double cylinder

交叉双圆柱在工程应用中较为广泛。为了解决交叉双圆柱绕流问题,该文应用Open FOAM开源代码对Re=200,不同间隙比G(间隙/直径,G=0.5,1,2和4)条件下60°交叉双圆柱流场进行了直接数值模拟(DNS)研究,得到了两圆柱的时均阻力系数,斯特劳哈尔数(St)以及间隙附近的流线图、涡量图和Ω涡识别图。研究表明,随着间隙比的增大,两圆柱的整体时均阻力系数值与St值的变化规律相反,时均阻力系数值先减小后增大,St值先增大后减小;分析了两圆柱在间隙附近的局部流态:尾涡(TV,G=0.5和1),项链涡(NV,G=2)和间隙中的涡脱落(SG,G=4);分析了上游圆柱远离间隙处的尾流流态,分别为K流态(G=0.5,1和2)及P流态(G=4),发现G=0.5,1和2时,下游圆柱尾流中存在大量不规则弱涡,G=4时,下游圆柱尾流强涡结构较明显,弱涡减少。

Crossed double cylinders are widely used in engineering.In order to solve the problem of flow around crossed double cylinders,in this paper uses the open source code of OpenFOAM is used to conduct direct numerical simulation(DNS)research on the flow field around 60°crossed double cylinders under Re=200 and different gap ratio G(gap/diameter,G=0.5,1,2,4),and then the time-mean drag coefficient of two cylinders,Strauhal number(St)and the flow chart,vorticity diagram andΩvortex identification diagram near the gap are obtained.The results show that with the increase of the gap ratio,the time-averaged drag coefficient of the two cylinders changes in the opposite way as the St value.The time-averaged drag coefficient decreases first and then increases,and the St value increases first and then decreases.The local flow patterns of two cylinders near the clearance are analyzed:including trail vortex(TV,G=0.5,1),necklace vortex(NV,G=2)and vortex shedding in the gap(SG,G=4).The wake flow patterns of the up stream cylinder far from the clearance are analyzed,which are k-flow(G=0.5,1,2)and p-flow(G=4)respectively.It is found that when G=0.5,1,2,there are a lot of irregular weak vortices in the downstream cylindrical wake,and when G=4,the strong vortex structure of the downstream cylindrical wake is obvious,and the weak vortices are reduced.