近壁圆柱绕流积沙线的形成机理研究

应用粒子图像测速(PIV)系统进行近壁圆柱绕流实验,探讨壁面积沙现象的机理.分别在两个动量损失厚度雷诺数1 092和796下,对两个不同直径的圆柱,取间隙比(圆柱与壁面间的距离与圆柱直径之比)0到1.5中的12个值进行实验,总结了不同情况下积沙线的形成特点.研究结果表明:积沙线形成的可能原因是由于圆柱对平板壁面边界层的影响,使得边界层流动在圆柱下游一到两倍圆柱直径的平板壁面处发生壁面分离,在分离区域流体速度减小,并且产生附着涡,流体运动挟带到此处的粒子速度减小,发生沉积而形成.

Experimental study on the sand accumulation phenomenon in flow around a circular cylinder near to a plane wall

The sand accumulation lines on the wall in flows around a near-wall circular cylinder were investigated by the experimental method through particle image velocimetry(PIV).The circular cylinders,having two different diameters,are set in a fully developed turbulent boundary layer.Under two Reynolds numbers(1092,796) of momentum loss thickness with 12 gap ratios(ratio of the gap between a circular cylinder and a plane wall to the diameter of the circular cylinder)from 0 to 1.5,the velocity vector distribution and the data of the sand accumulation lines are obtained.By analyzing the data,the possible mechanism has been demonstrated: the separation take places due to the interaction of the wake cylinder and the boundary layer of the plane wall,also some characteristics of the vortex structure that in the wake of cylinder near to a plane wall have been learned.