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Interaction of Acoustic Disturbances with Micro-Cavities for Ultrasonic Absorptive Coatings

Brès, Guillaume A. and Colonius, Tim and Fedorov, Alexander V. (2008) Interaction of Acoustic Disturbances with Micro-Cavities for Ultrasonic Absorptive Coatings. In: 5th AIAA Theoretical Fluid Mechanics Conference, 23–26 June 2008, Seattle, WA.

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Numerical simulations are performed to investigate the interaction of acoustic waves with an array of equally-spaced two-dimensional micro-cavities on an otherwise flat plate without external boundary-layer flow. This acoustic scattering problem is important in the design of ultrasonic absorptive coatings (UAC) for hypersonic laminar flow control. The reflection coefficient, characterizing the ratio of the reflected wave amplitude to the incident wave amplitude, is computed as a function of the acoustic wave frequency and angle of incidence, for coatings of different porosity, at various acoustic Reynolds numbers relevant to hypersonic flight. Overall, the numerical results validate predictions from existing theoretical modeling. In general, the amplitude of the reflection coefficient has local minima at some specific frequencies. A simple model to predict these frequencies is presented. The simulations also highlight the presence of resonant acoustic modes caused by coupling of small-scale scattered waves near the UAC surface. Finally, the cavity depth and the porosity are identified as the most important parameters for UAC design. Guidelines for the choice of these parameters are suggested.

Item Type:Conference or Workshop Item (Paper)
Related URLs:
URLURL TypeDescription Paper Paper
Brès, Guillaume A.0000-0003-2507-8659
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2008 by G. A. Bres, T. Colonius & A. V. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Published Online: 14 Jun 2012. The authors would like to acknowledge contributions to this work by Dr. Norm Malmuth, whose passionate work on diverse topics, including UAC, and generosity to his collaborators will be sorely missed. This work was supported by the Air Force of Scientific Research under Contract FA9550-06-C-0097.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-06-C-0097
Subject Keywords:Theoretical Fluid Mechanics
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Other Numbering System NameOther Numbering System ID
AIAA Paper2008-3903
Record Number:CaltechAUTHORS:20190718-165126161
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97258
Deposited By: Melissa Ray
Deposited On:22 Jul 2019 20:39
Last Modified:16 Nov 2021 17:30

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