上游双扰动对圆柱气动特性影响的数值模拟

通过用商用计算流体力学软件FLUENT 6.0中的SIMPLE方法求解二维非定常层流模型,对雷诺数Re=200时上游双扰动体对下游圆柱气动特性影响进行了数值模拟研究.计算结果表明当双扰动体相隔较近(H/d=1.1,1.33)时,其后形成单一的Karman涡街,它们对下游圆柱的干扰作用类似于单扰动体时的情况,但是流动结构发生变化的临界间距Lcri较之有效宽度相同的单扰动体的要大,因此可以推断出在该种布置下双扰动体和圆柱绕流会出现2种流动模式.在空穴流动模式下面,下游圆柱的阻力和升力脉动最多减小94%和79%,系统阻力(包括圆柱和扰动体)也能减小33%.而当双扰动体尾流为双Karman涡街时(双扰动体相隔较远H/d=3.33,5.0),圆柱迎风面部分区域仍受到来流的冲击作用,气动力减小有限.

Numerical simulation on upstream dual rods′ effect on aerodynamic characteristics of cylinder

Numerical simulation was constructed to investigate the upstream dual rods′ effect on the characteristics of the cylinder at Reynolds number 200. The unsteady laminar model was solved by SIMPLE method with CFD(computational fluid dynamics) commercial software package FLUENT 6.0. When the dual rods have small vertical interval (H/d=1.1, 1.33), there is only one Karman vortex street formed behind the rods. This case is much more similar to that of a single rod, but the critical spacing ratio for the flow pattern transition is larger than that of the single one. That means there are two different flow patterns with the spacing ratio increase, the cavity flow mode and the wake impinging mode. In the cavity flow mode, the maximum drag and RMS (root mean square) value of lift were reduced by 94% and 79%, respectively. The system drag (including the rod and the cylinder drag) was reduced by 33%. If there are two vortex streets behind the rods with large vertical interval (H/d=3.33, 5.0), the upwind surface of the cylinder is also impinged by the gap flow between the rods, which results in the drag and RMS value of lift reduction is limited.