固体颗粒在螺旋管流中的分布特性

二维天然挟沙水流由于重力引起的沉速作用,形成浓度上低下高的不均匀分布。对螺旋管流,可从流场的特点分析出固粒分布的中心对称与上下对称性。通过质量平衡微分方程的求解实例,说明其挟带浓度比普通平直管流高得多的固粒的力学原理是重力产生的沉速消失,而代之以低约两个数量级的扩张速度,从而形成沿迥转半径的较均匀的固粒分布。固粒沿截面分布的对称性与沿迥转半径分布的均匀性导致螺旋管流挟带固粒的高浓度,从理论上说明了螺旋管流可挟带高浓度的真实原因,更突出了研究螺旋管流输移固粒的深远意义。

Distribution characteristics of solid grains in spiral pipe flow

The non-uniform distribution of solid grains with the characteristic of "low up and high down" is formed in 2-D natural sand-laden flow due to the action of gravity. While in spiral flow, the distribution is symmetric about its center and horizontal axis. The solution of differential equations of equilibrium equations shows that in this case the flow carries much more grains than that in normal straight pipe flow. It might be explained by disappear of settling velocity. Instead of settling velocity an expanding velocity with magnitude of two orders less than the settle velocity occurs and leads to the more uniform distribution of grains along the rotating radius. The characteristics of symmetric and uniform distribution leads to the high concentration of grains carried in spiral pipe flow.