Drag reduction of Solid-liquid Suspension Using Macro-agglomeration Structure induced by Shear flow

众所周知，在剪切流场中，含有适当反离子的表面活性剂溶液会诱导形成纤维状胶束结构。当结构被诱导时，管流的阻力减小。基于这一事实，我们推测颗粒悬浮液中凝聚颗粒的结构也会产生同样的影响。因此，我们试图通过添加聚合物絮凝剂来降低悬浮流的压降。在本研究中，我们考察了管流压降随絮凝剂浓度的变化。用水流与悬浮流的摩擦因数之差与水流的摩擦因数之比的减阻率来评价阻力的变化。结果表明，在颗粒浓度为1%和10%的条件下，聚合物絮凝剂的悬浮液具有减阻作用。在相同的絮凝剂浓度下，絮凝剂的水溶液也会产生…更多的是减阻。但在一定条件下，溶液的减阻率低于含絮凝剂悬浮液的减阻率。结果表明，颗粒对减阻效果有增强作用，絮凝剂对减阻效果的影响随时间的延长而减弱。其中一个主要原因是剪切场和泵等设备对聚合物链的割断。结果表明，在颗粒悬浮液中加入絮凝剂比在絮凝剂溶液中加入颗粒有更大的增强作用。这导致了一种假设，即非均匀聚集归因于增强。因此，凝聚从非均相到均相的变化是影响减阻效果的另一个原因。通过对静止流体中絮凝的观察，发现当减阻作用增强时，形成了独立的团聚。事实表明，这种减阻作用是由团聚的颗粒引起的。这意味着，如果形成适当的团聚，在任何其他固液悬浮中都可以实现减阻。较少

It is known that a surfactant solution with appropriate counter ion induces the structure of fiber-like micelles in a shear flow field. When the structure is induced, the drag of the pipe flow is reduced. Based on the fact, we presumed that structure of agglomerated particles in a particle suspension also causes the same effect. Thus, we attempted to reduce the pressure drop of the suspension flow by adding a polymer flocculant. In this study, we investigated the change of the pressure drop of the pipe flow with the flocculant concentration. The change of the drag was evaluated by the drag reduction rate defined by the ratio of the difference of the friction factor between water flow and suspension flow to the friction factor of water flow.It was found that the suspension with polymer flocculant caused the drag reduction under the conditions of particle concentration 1 and 10vol%. In the same flocculant concentration, the water solution of the flocculant (=without particles) also cause … More d the drag reduction. However, the drag reduction rate of the solution was less than that of the suspension with flocculant under certain conditions. The fact shows that the particle enhances the drag reduction.The effect of the flocculant on the drag reduction decreases with time. One of the main causes is the cut of polymer chain by a shear flow field and/or by the equipment like a pump. It was found that the adding a flocculant into a particle suspension causes larger enhancement than the adding particles into the flocculant solution. It leads to an assumption that inhomogeneous agglomeration attributes to the enhancement. Thus, it was expected that the change of agglomeration from inhomogeneous to homogeneous is another cause of the decrease of the effect.From the observation of the flocculate in a stationary fluid, it was found that independent agglomerations were formed when the drag reduction was enhanced. The fact shows that the drag reduction is attributed by agglomerated particles. It leads to an expectation that the drag reduction can be achieved in any other solid-liquid suspension if proper agglomeration is formed. Less