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

已知在剪切流场中，表面活性剂溶液中加入适量的反离子可诱导纤维状胶束结构。当结构被诱导时，管道流动的阻力减小。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效果。因此，我们试图通过添加高分子絮凝剂来降低悬浮流的压降。本文研究了絮凝剂浓度对管道流压降的影响。阻力的变化由减阻率来评价，减阻率由水流与悬浮流之间的摩擦系数之差与水流的摩擦系数之比来定义。结果表明，在颗粒浓度为1和10vol%的条件下，高分子絮凝剂悬浮液的阻降效果明显。在相同的絮凝剂浓度下，絮凝剂的水溶液（=无颗粒）也能产生更大的减阻作用。但在一定条件下，该溶液的减阻率要小于加絮凝剂的悬浮液。事实表明，颗粒对减阻有一定的促进作用。絮凝剂的减阻效果随着时间的延长而降低。其中一个主要原因是聚合物链被剪切流场和/或泵等设备切割。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絮凝剂能产生更大的增强效应。这导致了一种假设，即非均匀集聚归因于增强。因此，可以预计，从非均匀到均匀的团聚变化是导致效果下降的另一个原因。通过对絮凝体在固定流体中的观察，发现当减阻能力增强时，絮凝体会形成独立的团聚体。事实表明，减阻主要是由于颗粒的凝聚作用。这导致了一种期望，即如果形成适当的团聚，在任何其他固液悬浮液中都可以实现减阻。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