过渡流下顺排圆柱列流动特性的可视化实验

Visualization Experiments on the Flow Characteristics of In-Line Cylindrical Column in Transition Flow Region

为研究过渡流下顺排圆柱列的流动规律,搭建了开式循环水槽。利用粒子图像测速(PIV)技术,在确定纵向间距(PT)及雷诺数(Re)的情况下,改变横向间距(Ps),从而对顺排圆柱列的瞬时场及时均流场进行可视化实验研究。实验结果表明在Re=150,PT=2.5D,Ps=2D^6D的工况下,上游圆柱与下游圆柱间距直接影响圆柱列流场换热效果。当Ps在2D^3D之间,上游圆柱与下游圆柱之间流场为回流死区,该区间换热效果差;Ps由3D增加至4D时,上游圆柱与下游圆柱之间流场由稳态变为非稳态;Ps由4D增加至6D时,上游圆柱与下游圆柱之间流场区域的洗刷效应减弱,且Ps=4D时,该区域的周期性更加明显。

In order to study the flow characteristics of in-line cylindrical column in transition flow,the open cyclic water tunnel and is set up in the experiment. The visualization experiments of in-line cylindrical column about instantaneous field and time-mean field are performed by using Particular Image Velocimetry(PIV)method of fixing the?longitudinal?spacing and Reynolds number,and then changing the horizontal spacing. The experimental results demonstrate that the heat transfer effect of the flow field is directly affected by the spacing between the upstream cylinders and the downstream cylinders in the case of Re=150,P_T=2.5 D,P_s=2 D^6 D. When the horizontal spacing is changed between 2 D and 3 D,the flow field between the upstream cylinders and the downstream cylinders is a dead zone with poor effect in heat transfer. When the horizontal spacing is increased from 3 D to 4 D,the flow field between the upstream cylinders and the downstream cylinders is changed from steady state to unsteady state. When the horizontal spacing is increased from 4 D to 6 D,the scouring effect of the flow field between the upstream cylinders and the downstream cylinders decreases.In the case of the horizontal spacing is 4 D,the periodicity of the region is more pronounced.