Nonlinear Dynamics of "Triggering Controllers"

本文拟研究一类典型流体系统的非线性动力学和控制：后向台阶流动、海崖体两个尖角的流动分离以及单翼型或多翼型的高频颤振。 在此，“控制”不应按传统意义解释。 最近的“控制”努力集中在触发流体剪切层的不稳定性;通过创建某些涡动态相互作用，系统性能往往显着改善。所提出的研究旨在获得对系统的非线性动态过程和分叉结构的理解，以便有可能系统地综合这种触发控制器，而不是依赖于特设的试错。 该方法包括建立低阶涡模型，捕捉系统的基本特征，然后进行规范形和分叉分析。 人们相信，从threecanonical问题的经验教训将在这里研究适用于一个广泛的类流体流动问题，其性能是敏感tononlinear涡动力学剪切层内。 该项目将支持PI和联合技术研究中心之间的密切合作，该研究中心的工程师/科学家正在寻找将触发控制器纳入几种产品的实用方法。 此外，拟议的项目将形成一个焦点，产生几个本科生研究项目。PI观察到，这样的经历，其中大学生作出了有意义的贡献，往往会激发他们的动机和追求更高学位的愿望。

The investigator proposes to study the nonlinear dynamics and controlof a class of canonical fluid systems: flow over a backward facingstep, flow separation from two sharp convex corners of a bluff body,and high frequency flutter of one or multiple airfoils. Here,"Control" should not be interpreted in the traditional sense. Recent"control" efforts have focused on triggering instabilities in thefluid shear layers; by creating certain vortex dynamic interactions,system performance often improves dramatically. The proposed researchseeks to gain an understanding of the nonlinear dynamic processes andthe bifurcation structure of the systems, so that it may be possibleto synthesize such triggering controllers systematically, rather thanrelying on ad hoc trial and error. The approach consists ofconstructing low order vortex models that capture essential featuresof the systems, and then performing normal form and bifurcationanalyses. It is believed that lessons learned from the threecanonical problems to be studied here will be applicable to a broadclass of fluid flow problems whose performance is sensitive tononlinear vortex dynamics within shear layers. The project willsupport close collaboration between the PI and United TechnologiesResearch Center, whose engineers/scientists are searching forpractical ways of incorporating triggering controllers into severalproducts. Furthermore, the proposed project will form a focal pointaround which to generate several undergraduate research projects. ThePI has observed that such experiences, in which undergraduates makemeaningful contributions, often buoy their motivation and desire forpursuing advanced degrees.