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

非技术摘要：湍流流过壁面时会产生摩擦阻力，这一特性决定了通过管道泵油的成本、洪水中河流的排水能力以及其他实际意义上的量。关于摩擦阻力，人们知道得很多，大部分是通过在管道或明渠中测量摩擦阻力的大量实验得到的，然而，在摩擦阻力和流动中湍流涡流的统计数据之间还没有已知的联系。该项目的目标是实验测试最近提出的理论，这将使我们能够预测摩擦阻力的湍流涡流的统计知识。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，其中可以创建具有不同类型统计数据的流动。如果得到证实，该理论可以提供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试剂的阻力改变效果的关键。在伊利诺伊州和匹兹堡，研究生和本科生将接受包括工程和基本凝聚态物理学在内的多学科重点培训，向本科生和女性介绍湍流研究。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，并参加教师研讨会。技术摘要：湍流流过墙壁时会受到摩擦阻力，这种流动特性决定了通过管道泵油的成本，洪水中河流的排水能力，以及其他实际感兴趣的量。虽然对摩擦阻力有很多了解，但摩擦阻力和湍流谱之间没有已知的联系（即，流中湍流波动的统计）。这个项目的目标是实验测试最近提出的理论，将提供失踪的“光谱链接”。 如果得到证实，该理论可能是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试剂的阻力改变效应的关键。该理论已经在二维肥皂膜湍流中进行了测试，其光谱类型被称为拟能级联，但到目前为止，还不可能创建类似的流动，其光谱类型被称为逆能量级联。 发展了一种利用逆能量级联产生肥皂膜流的方法，并将其用于测量逆能量级联支配的二维湍流的摩擦阻力，完成了谱链的实验验证。 在伊利诺伊州和匹兹堡，PI将培养研究生和本科生，多学科的重点包括工程和基础凝聚态物理，介绍本科生和妇女研究湍流。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，并参加一个教师讲习班。

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.