Nonlinear Dynamics of "Triggering Controllers"

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

The investigator proposes to study the nonlinear dynamics and control of a class of canonical fluid systems: flow over a backward facing step, 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 the fluid shear layers; by creating certain vortex dynamic interactions, system performance often improves dramatically. The proposed research seeks to gain an understanding of the nonlinear dynamic processes and the bifurcation structure of the systems, so that it may be possible to synthesize such triggering controllers systematically, rather than relying on ad hoc trial and error. The approach consists of constructing low order vortex models that capture essential features of the systems, and then performing normal form and bifurcation analyses. It is believed that lessons learned from the three canonical problems to be studied here will be applicable to a broad class of fluid flow problems whose performance is sensitive to nonlinear vortex dynamics within shear layers. The project will support close collaboration between the PI and United Technologies Research Center, whose engineers/scientists are searching for practical ways of incorporating triggering controllers into several products. Furthermore, the proposed project will form a focal point around which to generate several undergraduate research projects. The PI has observed that such experiences, in which undergraduates make meaningful contributions, often buoy their motivation and desire for pursuing advanced degrees.