水—浮泥界面水沙分布及其对浮泥悬扬速率的影响

Distributions of velocity and sediment concentration on the water-mud interface and influences on the entrainment rate of fluid mud

为探究浮泥层悬扬过程中水-浮泥界面的水沙变化特性,以高岭土为浮泥试样,在环形水槽中测定近底层水流结构和悬沙浓度分布,以此推求浮泥悬扬速率。结果表明：均匀剪切水流作用下水-浮泥界面水沙分布特性是影响浮泥悬扬速率的关键因素;近底层流速与浓度梯度随悬扬时间均呈减小趋势,即交界面处流体的掺混作用使水-浮泥分层流密度差显著减小,界面上浮泥层稳定性减弱,浮泥悬扬速率相应增强;同时考虑浮泥层对交界面处水流结构的影响,以界面实测局部流速代替断面平均流速对悬扬速率的经验公式进行了修正,所得计算结果更为合理。

Experimental study on the entrainment of fluid mud is carried out in an annular flume with commercial kaolinite,to explore characteristics of velocity and sediment concentration on the interface of water-fluid mud. The vertical distribution of sediment concentration and flow velocities are measured,and the entrainment rate of fluid mud were calculated. The results show that,the vertical distribution of velocities and sediment concentrations are the key factors to determine the entrainment rate of fluid mud under the influences of currents. Both the gradients of velocity and sediment concentration decrease with time,which show that the distribution of sediment concentration becomes uniform in the vertical direction. Therefore,the fluid mud layer becomes unstable and easy to be eroded. To take into account the effects of fluid mud on the flow structure,the measured local velocity is adopted in empirical equations instead of the depth-averaged flow velocity,with which more reasonable results are given.