Flow of Elastic Liquids

该提案涉及含有溶解的聚合物的液体，这通常使液体具有弹性和粘性。聚合物通常被添加到液体中以使材料更粘稠-油漆和墨水是示例-但聚合物也使液体具有弹性，并且这种额外的流体特性可以影响流动。例如，在喷墨打印中，墨水的弹性会导致不需要的卫星液滴。有时添加聚合物仅仅是为了弹性提供的改进。两个发展良好的应用是：农业喷雾，因为弹性改善了涂层的表面沉积;和湍流管流，因为弹性应力降低了驱动压力。添加的聚合物的量通常是微小的，但效果可能是戏剧性的。例如，在湍流管流中，增加百万分之十可以将所需压力降低50%。粘度是流体的一个明显属性-液体被称为厚或薄-但弹性通常不太明显。最明显的表现可能是粘稠，如唾液和蛋清。

The proposal concerns liquids containing a dissolved polymer, which generally makes the liquid elastic as well as viscous. Polymers are often added to liquids to make the material more viscous – paint and ink are examples – but the polymer also makes the liquid elastic, and this additional fluid property can affect a flow. In inkjet printing, for example, the ink’s elasticity can cause unwanted satellite droplets. Sometimes the polymer is added solely for the improvement provided by elasticity. Two well-developed applications are: to agricultural spraying because elasticity improves surface deposition of the coating; and to turbulent pipe flow because elastic stresses reduce the driving pressure. The amount of added polymer is often minute but the effect can be dramatic. In turbulent pipe flow, for instance, the addition of 10 parts per million can reduce the required pressure by 50%. Viscosity is an obvious property of a fluid - liquids are referred to as thick or thin - but elasticity is generally much less evident. The most visible manifestation is probably stringiness, as seen with saliva and egg whites.