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Acoustic Properties of Porous Coatings for Hypersonic Boundary-Layer Control

Brès, Guillaume A. and Colonius, Tim and Fedorov, Alexander V. (2010) Acoustic Properties of Porous Coatings for Hypersonic Boundary-Layer Control. AIAA Journal, 48 (2). pp. 267-274. ISSN 0001-1452.

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Numerical simulations are performed to investigate the interaction of acoustic waves with an array of equally spaced two-dimensional microcavities on an otherwise flat plate without external boundary-layer flow. This acoustic scattering problem is important in the design of ultrasonic absorptive coatings 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 porosities, 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 coating surface. Finally, the cavity depth and the porosity are identified as the most important parameters for coating design. Guidelines for the choice of these parameters are suggested.

Item Type:Article
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URLURL TypeDescription DOIArticle
Brès, Guillaume A.0000-0003-2507-8659
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2009 by G.A. Brès, T. Colonius, and A.V. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Presented as Paper 3903 at the 5th AIAA Theoretical Fluid Mechanics Conference, Seattle, WA, 23–26 June 2008; received 4 September 2008; revision received 12 February 2009; accepted for publication 2 February 2009. This work was supported by the U.S. Air Force Office of Scientific Research under contract FA9550-06-C-0097. The authors would like to acknowledge contributions to this work by Norm Malmuth, whose passionate work on diverse topics, including ultrasonically absorptive coating, and generosity to his collaborators will be sorely missed.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-06-C-0097
Issue or Number:2
Record Number:CaltechAUTHORS:20100308-144328976
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17699
Deposited By: Tony Diaz
Deposited On:12 Mar 2010 22:43
Last Modified:03 Oct 2019 01:32

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