Application of Acoustic Metamaterials in Boundary Layer Instability Control

Master thesis (2021)

Authors

C.L.A. de Koning Aerospace Engineering

Contributors

M. Kotsonis Aerodynamics - Aerospace Engineering (mentor)
Theodorus Michelis Aerodynamics - Aerospace Engineering (mentor)
Faculty
Aerospace Engineering, Aerospace Engineering
Copyright: © 2021 Coert de Koning
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Published Date

23-04-2021

Language

English

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Faculty

Aerospace Engineering

Abstract

To achieve delay of laminar-to-turbulent transition of boundary layers, the application of acoustic metamaterial concepts is investigated. This is done analytically, numerically and experimentally by studying the interaction between a Helmholtz resonator and a TS wave. A Helmholtz resonator can serve as a meta-atom in a metamaterial. The desired wall controller property of a metamaterial to suppress TS waves is evaluated. This study shows that TS wave attenuation is achieved if the wall-normal velocity from a metamaterial is in-phase with the TS wave pressure. TS wave amplification is obtained if the pressure and velocity are more than (approximately) 90 degrees out of phase. The p-v phase relation corresponding to a Helmholtz resonator only remains in the amplification regime. Therefore, the conclusion is drawn that a single Helmholtz resonator can only amplify TS waves. If an acoustic metamaterial concept is found where pressure and wall-normal velocity are in-phase, this can be useful in boundary layer instability control.