Flow of Elastic Liquids

弹性液体的流动

• 批准号: RGPIN-2015-06338
• 负责人: James, David
• 金额: $ 1.82万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680724
• 关键词: Flow; Elastic; Liquids

***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. ******This grant application focusses on four flows in which the effect of elasticity is significant. For one of these, polymer is added for a specific benefit: namely, to water jet micromachining to improve resolution or precision. For the other three flows, polymer is an inherent constituent of the test fluids, and so the experimental liquids are elastic as well as viscous. One experiment is flow past a cylinder, carried out under microscopic conditions so that results can help explain how micro-organisms use their flagella to swim in mucus. Another experiment is flow through an array of rods, the array being a model of a fibrous porous medium, with application to fibre-reinforced plastics. The third is stagnation point flow. Because it is component of all the other flows, results from the study will help in explaining the elastic effects observed in those flows.******The primary objective of the program is to understand the role of elasticity in these experimental flows, that is, to identify when the property is operative, to quantify its effect, and to determine how the stresses caused by elasticity alter a flow. The latter three experiments will be conducted with special viscoelastic fluids - liquids which are elastic but have constant viscosities - that will enable elastic effects to be cleanly separated from viscous effects so that the role of elasticity can be assessed. Initial results with the rod arrays, for instance, have indicated that the resistance to flow caused by elasticity alone can be several times the resistance caused by viscosity, demonstrating the importance of elasticity.

* 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--液体被称为稠的或稀的--但弹性通常不那么明显。 最明显的表现可能是粘稠，如唾液和蛋清。 ** 本补助金申请侧重于四个流动，其中弹性的影响很大。 对于其中之一，添加聚合物是为了一个特定的好处：即，水射流微加工，以提高分辨率或精度。 对于其他三种流动，聚合物是测试流体的固有成分，因此实验液体是弹性的以及粘性的。 其中一个实验是在显微镜下进行的圆柱体流动，以便结果可以帮助解释微生物如何使用鞭毛在粘液中游泳。 另一个实验是通过一个阵列的杆，阵列是一个模型的纤维多孔介质，与应用程序的纤维增强塑料。 三是驻点流动。 由于它是所有其他流动的组成部分，因此研究结果将有助于解释在这些流动中观察到的弹性效应。*该计划的主要目标是了解弹性在这些实验流动中的作用，也就是说，确定何时该属性起作用，量化其影响，并确定弹性引起的应力如何改变流动。 后三个实验将使用特殊的粘弹性流体-具有弹性但粘度恒定的液体-进行，这将使弹性效应与粘性效应完全分离，从而可以评估弹性的作用。例如，杆阵列的初步结果表明，仅由弹性引起的流动阻力可以是由粘性引起的阻力的几倍，这证明了弹性的重要性。