明渠挟沙水流的颗粒相平均速度及速度滑移

Mean Velocity Profiles of Particulate Phase and Interphare Velocity Slip in Sediment-laden Open Channel Flows

基于颗粒相动理学模型所确立的颗粒相基本方程和本构关系 ,导出了明渠挟沙水流中固液两相平均速度差的表达式 ,表明相间速度差与两相的垂向脉动强度、脉动切应力、水下重力、剪切升力、颗粒弛豫时间等有关 ,与两相沿流向脉动强度无关。运用水流速度的窦国仁公式 ,计算了颗粒相速度的垂线分布 ,分析了相间速度差的垂线分布特性 ,结果与试验资料吻合很好。表明相间速度差呈现出水面小、水底大的分布形式 ;细小颗粒的速度差近似为零 ,粗重颗粒的速度差明显。

An algebraic expression for mean slip velocity in sediment-laden open channel flows was developed from the set of conservation equations with the constitutive relationships of particulate phase based on the kinetic theory.The mean slip velocity is associated with the shear lift force,underwater gravity and response time of particles,and with the vertical velocity fluctuations and turbulence shear stresses of both phases.With the formula proposed by Dou for the distributin of water velocity,mean particle velocity profiles were predicted and the characteristics of mean slip velocity were theoretically analyzed.The predicted profiles agree with expperimental data very well.It shows that the slip velocity is small on the flow surface and gets larger toward the bottom.The slip of fine particles is negligible. Whereas the slip velocity of coarse and heavy particles is significant with an obvious maximum value near the channel bed.