CAREER: Enabling Methods for Modeling and Control of Transitional and Turbulent Wall-Bounded Shear Flows

本文介绍了过渡性和湍流壁面剪切流的建模和控制的新方法。提出的工作的一个重要属性是，它建立在最近的研究表明不确定性的重要性，如自由流湍流和壁面粗糙度，在渠道，管道和边界层。通过无传感器机制减少阻力是一项很有前途的技术，因为它代表了一种更简单的替代方案，即通过壁挂式传感器和执行器阵列进行反馈流控制。尽管一些数值和实验研究表明，适当设计的无传感器策略可以显著降低阻力，但充分利用这些方法的一个障碍是缺乏设计和优化的理论框架。这种分析工具的缺乏极大地阻碍了无传感器方案的综合以及它们对不同流型的扩展。PI将为无传感器流量控制策略的设计和优化开发一个系统理论范式。新范式是众所周知的振动控制原理的时空模拟，其中通过在系统系数中引入零均值振动来改变系统的动态特性。PI的理论发现将有助于实现更有效的减阻策略，并为各种表面驱动技术的设计提供指导。由于分布式系统在现代技术中变得无处不在，本提案的教育目标是使分布式概念在本科生和早期研究生阶段更加普及。PI将推出一门新的入门课程，该课程将强调以结构特性、实际应用和物理解释为特征的系统类。PI将与明尼苏达科学博物馆合作，组织关于自然界中流量控制策略多样性的流行讲座。几个视频演示将用来说明如何从自然世界的观察激励研究，工程设计和技术发展。PI的目标是让高中生尽早了解控制工程的核心作用，将自然飞行和游泳的效率引入人造系统。流建模与控制是系统与控制理论中一个很有前途的活跃研究领域。操纵和控制流体流动的能力在许多应用中至关重要，包括管道运输，空气和水车辆的阻力减少，以及化学反应器和内燃机的混合增强。成功的流量控制策略的潜在好处是巨大的；从节省燃料的经济收益到改善涉及流体流动的工程系统的性能。由于表面摩擦阻力直接转化为飞机、船舶和潜艇的大量燃料消耗，因此迫切需要开发和利用本工作中提出的先进理论和计算技术。

This proposal introduces new methods for modeling and control of transitional and turbulent wall-bounded shear flows. An important attribute of the proposed work is that it builds upon recent research manifesting the significance of uncertainty, such as free-stream turbulence and wall roughness, in channels, pipes, and boundary layers. Drag reduction by sensorless mechanisms is a promising technology, as it represents a much simpler alternative to feedback flow control with wall-mounted arrays of sensors and actuators. Although several numerical and experimental studies indicate that properly designed sensorless strategies yield significant drag reduction, an obstacle to fully utilizing these approaches is the absence of a theoretical framework for their design and optimization. This lack of analytical tools greatly impedes the synthesis of sensorless schemes as well as their extension to different flow regimes. The PI will develop a system-theoretic paradigm for design and optimization of sensorless flow control strategies. The new paradigm is a spatio-temporal analog of the well-known principle of vibrational control, where the system's dynamical properties are altered by introducing zero-mean vibrations into the system's coefficients. The PI's theoretical findings will enable more efficient drag reduction strategies and provide guidelines for design of various surface-based actuation techniques. Since distributed systems are becoming ubiquitous in modern technology, the educational goal of this proposal is to make distributed concepts more pervasive at the undergraduate and early graduate level. The PI will launch a new introductory course that will emphasize classes of systems characterized by their structural properties, practical applications, and physical interpretations. In collaboration with the Science Museum of Minnesota, the PI will organize popular lectures on diversity of flow control strategies in nature. Several video demonstrations will be used to illustrate how observations from the natural world motivate research, engineering design, and technology development. The PI's goal is to provide high-school students with an early exposure to the central role of control engineering in bringing the efficiency of natural fliers and swimmers to man-made systems. Flow modeling and control is a promising active research area in systems and control theory. The ability to manipulate and control fluid flows is of paramount importance in many applications including transport in pipes, drag reduction for air and water vehicles, and mixing enhancement in chemical reactors and combustion engines. The potential benefits of successful flow control strategies are enormous; they range from economic gains in fuel savings to improved performance of engineering systems involving fluid flows. Since skin-friction drag directly translates into large fuel consumption for airplanes, ships, and submarines, there is a critical demand for development and utilization of advanced theoretical and computational techniques proposed in this work.