Title

The Effects of Deployable Surface Topography Using Liquid Crystal Elastomers on Cylindrical Bodies in Flow

Date of Award

2023

Degree Name

M.S. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Richard Beblo

Abstract

Adaptive materials with programmable surface topography control can be utilized for selective boundary-layer tripping. Liquid crystal elastomers (LCE) have lately gained significant attention to be leveraged to enable these changes via repeatable and controlled out-of-plane deformations. The LCE can be preferentially aligned with circumferential patterns through the thickness of the film, which yields a predictable conical out-of-plane deformation when thermally activated. These reversible and predictable deployments can be utilized to develop a multifunctional surface designed for bodies in flow. This thesis concentrates on the experimental research of LCE behavior for purposes of active flow control via controlled surface topography. First, the deformations of the 12.7-mm diameter patterned LCE samples were characterized using digital image correlation in a controlled pressure chamber under positive and negative gauge pressures. The LCE's performance was highly dependent upon boundary conditions, specimen dimensions, and imprinted defect location relative to the boundary conditions, thus leading to the refinement of the LCE formulation to allow for a higher modulus. Then, to exhibit the potential for flow control, varying arrangements of representative topographical features were 3D-printed and characterized in a preliminary wind tunnel experiment using particle image velocimetry (PIV). Results demonstrated that a two-row arrangement of 1.5-mm feature height produced an asymmetric wake about a 73-mm cylinder, reducing drag while generating lift. Subsequently, a proof of concept model with active LCE elements was fabricated and tested using a force-balance instead of PIV in a wind tunnel. The results of the conceptual model demonstrated that LCEs exhibit the necessary performance to be used in flow control applications.

Keywords

Aerospace Engineering, Aerospace Materials, Materials Science, Engineering, Mechanical Engineering, Liquid crystal elastomers, Active flow control, Controllable surface topography, Digital image correlation, Wind tunnel analysis on patterned cylindrical bodies in flow

Rights Statement

Copyright © 2023, author

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