絮团与颗粒不等速沉降碰撞研究

絮团和单个颗粒的碰撞、粘结规律对于深入理解粘性泥沙不等速沉降引起的絮凝具有重要意义。在暂不考虑絮团与颗粒间相互作用力的条件下,用不同密度球形颗粒近似描述絮团,利用格子Boltzmann方法模拟了不同密度絮团和单个颗粒静水沉降过程,分析了絮团和颗粒相对运动轨迹和碰撞效率。模拟结果表明,絮团和单个颗粒不等速沉降碰撞过程中,当较大粒径的絮团沉降速度快但密度较小时,单个颗粒相对于絮团运动可能形成封闭轨迹,絮团和颗粒间粘结概率几乎为零,絮团很难通过捕捉单个颗粒而形成更大絮团。

Study of particle-cluster aggregation in differential settling

The particle-cluster collision and aggregation play an important role in differential settling.The settling processes of spheres with different sizes and densities in quiescent water are calculated using Lattice Boltzmann method when interparticle forces between spheres are negligible,in which the spheres with different densities stand for flocs approximately.Relative trajectory and collision efficiency calculations for particles indicate that a closed region of relative trajectories may occur during the particle-cluster settling and collision when the cluster is bigger than the particle,but with low density and high settling velocity.The collision efficiency between the cluster and particles is almost zero so that the cluster can hardly capture a single particle to aggregate the bigger cluster under this condition.