EAGER: Collaborative Research: Exploring the inverse cascade in two-dimensional turbulent soap films

非技术摘要：流过壁面的湍流会经历摩擦阻力，这一特性决定了通过管道泵送石油的成本，决定了洪水时河流的排水能力，以及其他一些实际意义。人们对摩擦阻力的了解很多，主要来自于在管道或明渠中测量摩擦阻力的大量实验，然而，在流动中摩擦阻力和湍流漩涡的统计数据之间还没有已知的联系。该项目的目标是通过实验测试最近提出的一个理论，该理论将使我们能够根据湍流涡流的统计知识来预测摩擦阻力。这将通过测量一种二维湍流来实现，这种湍流可以在非常薄的肥皂膜中实现，在那里可以创建具有不同类型统计的流。如果得到证实，该理论将为理解石油管道中使用的聚合物添加剂、洪水中河流中发现的颗粒悬浮物、水处理厂中发现的夹带气泡以及其他已知影响流量统计数据的物质改变阻力的作用提供关键。在伊利诺伊大学和匹兹堡大学，研究生和本科生将接受包括工程和基础凝聚态物理在内的多学科重点培训，向本科生和女性介绍湍流研究。这些pi将合作推广到6-12年级，与一所女子中学合作设计一个关于肥皂膜物理、湍流、混沌和光学的单元，并参加一个教师研讨会。技术摘要：流过壁面的湍流会经历摩擦阻力，这一特性决定了通过管道抽水的成本，决定了洪水时河流的排水能力，以及其他一些实际意义。虽然对摩擦阻力有很多了解，但在摩擦阻力和湍流谱（即流动中湍流波动的统计数据）之间没有已知的联系。这个项目的目标是通过实验测试最近提出的一个理论，该理论将提供缺失的“光谱链接”。如果得到证实，该理论将成为理解石油管道中使用的聚合物添加剂、洪水中河流中发现的颗粒悬浮物、水处理厂中发现的夹带气泡以及其他已知影响光谱的物质的减阻作用的关键。该理论已经在二维肥皂膜湍流中进行了测试，这种湍流具有被称为熵级联的光谱类型，但到目前为止，还不可能创建具有被称为逆能量级联的光谱类型的类似流动。提出了一种利用逆能量级联产生皂膜流的方法；然后将其用于测量逆叶栅主导的二维湍流的摩擦阻力，完成谱链的实验验证。在伊利诺伊大学和匹兹堡大学，pi将培养研究生和本科生，他们的多学科重点包括工程和基础凝聚态物理，将本科生和女性引入湍流研究。这些pi将合作推广到6-12年级，与一所女子中学合作设计一个关于肥皂膜物理、湍流、混沌和光学的单元，并参加一个教师研讨会。

NON-TECHNICAL ABSTRACT: Turbulent flows past a wall experience frictional drag, the property of a flow that sets the cost of pumping oil through a pipeline, the draining capacity of a river in flood, and other quantities of practical interest. Much is known about the frictional drag, mostly from extensive experiments in which the frictional drag was measured in pipes or open channels, yet, there has been no known link between the frictional drag and the statistics of the turbulent eddies in the flow. The project' goal is to test experimentally a recently proposed theory that will allow us to predict the frictional drag from a knowledge of the statistics of the turbulent eddies. This will be achieved through measurements in a type of two-dimensional turbulent flow that may be realized in very thin soap films, where it is possible to create flows with different types of statistics. If confirmed, the theory could provide the key to understanding the drag-altering effects of polymeric additives used in oil pipelines, particulate suspensions found in rivers in flood, entrained bubbles found in water-treatment plants, and other agents known to affect the statistics of the flow. At Illinois and Pittsburgh, graduate and undergraduate students will be trained with a multidisciplinary focus encompassing engineering and fundamental condensed matter physics, introducing undergraduates and women to research in turbulence. The PIs will collaborate on outreach to grades 6-12, work with an all-girl's middle school to devise a unit on soap film physics, turbulence, chaos and optics, and participate in a teacher's workshop.TECHNICAL ABSTRACT: Turbulent flows past a wall experience frictional drag, the property of a flow that sets the cost of pumping oil through a pipeline, the draining capacity of a river in flood, and other quantities of practical interest. While much is known about the frictional drag, there has been no known link between the frictional drag and the turbulent spectrum (i.e., the statistics of turbulent fluctuations in the flow). The goal of this project is to test experimentally a recently proposed theory that would provide the missing "spectral link". If confirmed, the theory could prove key to understanding the drag-altering effects of polymeric additives used in oil pipelines, particulate suspensions found in rivers in flood, entrained bubbles found in water-treatment plants, and other agents known to affect the spectrum. The theory has been tested in two-dimensional soap-film turbulent flows with the type of spectrum known as the enstrophy cascade, but so far it has not been possible to create similar flows with the type of spectrum known as the inverse energy cascade. A method to create soap-film flows with the inverse energy cascade will be developed; it will then be used to measure the frictional drag of inverse cascade dominated 2D turbulence, completing the experimental verification of the spectral link. At Illinois and Pittsburgh, the PIs will train graduate and undergraduate students with a multidisciplinary focus encompassing engineering and fundamental condensed matter physics, introducing undergraduates and women to research in turbulence. The PIs will collaborate on outreach to grades 6-12, working with an all-girl's middle school to devise a unit on soap film physics, turbulence, chaos and optics, and participating in a teacher's workshop.