不同直径串列双圆柱的可视化实验研究（英文）

Visualization Experiments on the Circle Cylinders with Unequal Diameters in Tandem Arrangement

主要研究了不同直径串列双圆柱的流动特性.在已有的开式循环水槽实验台的基础上,通过PIV实验对雷诺数(Re)为200时不同间距比(P_s/D)下不同直径串列双圆柱的流动特性进行了研究.实验结果表明:1)随着圆心距的增加,不同直径串列双圆柱流场型态出现了两种流动机制.2)随着圆心距的增加,上游小圆柱后出现了不同尺度的雷诺应力等值线.当圆心距较小时,上游小圆柱后面没有雷诺应力等值线的出现,当增大到4D以上时,上游圆柱后有雷诺应力等值线出现.3)当圆心距较小时,上游小圆柱与下游大圆柱间的流场相对稳定,随着圆心距的增大两圆柱间的流场开始出现扰动,但扰动强度没有下游圆柱强,当圆心距进一步增大时两圆柱间与下游大圆柱后的都出现了较大的扰动.上述流动特性的研究将为不同直径串列双圆柱的传热研究提供理论基础.

The flow characteristics of circle cylinders with unequal diameters in tandem arrangements were studied.On the basis of an open-loop,recirculating water tunnel,the flow characteristics of circle cylinders with different spacing ratio(Ps/D)were investigated by the method of particular image velocimetry(PIV)for Re=200.It was found that:1)Two flow-pattern regimes including alternating behavior of reattachment and vortex shedding and independent vortex shedding behavior at various spacing ratios have been identified.2)With the increase of spacing ratio,different contours of Reynolds stress from the upstream smaller cylinders can be observed.3)The flow between the two cylinders is steady when the spacing ratio is small.With the increase of the spacing ratio the flow between the two cylinders is turbulent,but the turbulence intensity is lower than the downstream cylinder.When the spacing ratio further increases the turbulence intensity of the flow behind the two cylinders becomes stronger.The findings can provide theoretical reference for the further heat transfer research of circle cylinders with unequal diameters in tandem arrangements.