摘要
非牛顿流体中固体颗粒的运动可分为推移质、悬移质和中性悬浮质运动.颗粒在非牛顿流体中的沉速显著小于清水中的,这反映了非牛顿流体中颗粒运动的阻力系数显著增大.非牛顿体明渠流中一般推移质运动适合拜格诺公式,但比水流中的推移质运动更容易发展成层移质运动,此时输沙率比拜格诺公式的值大.当非牛顿体流动转为层流时,表层流速加快而挟带的推移质显著减少. 与水流相比,非牛顿流体的悬移质挟沙力大得多,但冲刷率在小流量时较小,大流量时则大得多.大流量非牛顿流体明渠流中常发生严重冲刷,在一定条件下可能发生“揭河底”冲刷.试验中复演了这一特殊的冲刷现象.
The solid grains in non-Newtonian flow are referred to bed load, suspended load and neutral-buoyant load. The non-Newtonian fluid is of high viscosity and yield stress, so that the falling velocity of grain is obvious ly smaller than that in clear water. This implies a larger drag coefficient in non-Newtonian flow. The rate of bed load transport in non-Newtonian flow in open channel seems to be basically in line with the Bagnold equation. But in non-Newtonian turbulent flow, a high intensity of bedload motion-the laminated load motion can develop. The rate of bedload transport is higher than Bagnold equation. As the flow turns into laminar flow due to the increase in viscosity and yield stress of the non-Newtonian fluid, the rate of bed load transport reduces sharply while the velocity of the flow increases.The capacity of non-Newtonian flow to carry suspended load is largely higher than water flow, and the rate of scouring sediment from channel bed is smaller at low flow discharge and sharply increases at high discharge. This interprets the serious erosion of channel bed during high-discharge non-Newtonian flow. If the channel bed consists of sand and a thin layer of cohesive material, it can be torn off in blocks, turning around and standing up, towering in the flow surface and collapsing.
出处
《泥沙研究》
CSCD
北大核心
1990年第3期1-12,共12页
Journal of Sediment Research
基金
国家自然科学基金
