CAREER: Morphing Surfaces for Flow Control

California Institute Of Technology, Pasadena CA

Investigators

Abstract

CBET-0747672 McKeon This integrated research and education study investigates the physics associated with the interaction of boundary layer flows with morphing surfaces (defined here as thin skins capable of generating small, distributed or discrete, morphological or geometrical perturbations to the wall boundary condition). Fundamental questions to be addressed include how well can the characteristics of a boundary layer be manipulated via a morphing surface, what additional fundamental understanding of fluid physics can be gained from this new means of activation and how should graduate students best be prepared for this interdisciplinary research? An interdisciplinary approach will focus on: identification of the flow physics in new regimes that can now be interrogated using active materials; in situ characterization of the interaction between boundary layer flows and morphing surfaces; and investigation of open-loop actuation using surface morphing as a precursor to closed-loop control. Arrays of individually-addressable micro- or nano- actuators will be replaced with a coherent surface, or "skin" capable of either morphological changes or small adaptation of local geometry. Activation of properly designed morphing surfaces represents minimal control effort, with the potential for relatively simpler models relating the input to resultant structural changes in the flow. This research will expand our understanding of flow physics in receptive flows into a parameter range not previously accessible, or perhaps imaginable, before the advent of some newer materials. Classical hypotheses can then be revisited for canonical flows after the introduction of time-dependent wall motion and providing potential means for actuation for future closed-loop control work. Experiments on morphing surfaces also promise further insight into fundamental questions concerning a statically rough wall, mixing and vorticity flux in boundary layers. Broader impacts address environmental concerns and expanded air vehicle performance using active control or optimization of vehicular boundary layers via artificial manipulation of the boundary layer structure. This research will show how this could be achieved without large weight or structural penalties, and ultimately leading to a design feature for new vehicles. Collaborations with the active materials industry and a leading controls researcher seek to unite multiple fields to address this highly interdisciplinary topic. The educational goal is to develop a synergistic training scheme in flow control, suitable for addressing the research described here and educating graduate researchers to inhabit the middle ground between traditional disciplines associated with flow control, including fluid mechanics, control, dynamics and solid mechanics. This will culminate with a graduate level course designed to unify experimental, computational and modeling approaches to tackle advanced flow control problems. Outreach will target general public interest in fluid dynamics, with emphasis on girls of high school age and a continuing commitment to undergraduate research participation.