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Instability of Hypersonic Boundary Layer on a Wall with Resonating Micro-Cavities

Fedorov, Alexander V. and Brès, Guillaume A. and Inkman, Matthew and Colonius, Tim (2011) Instability of Hypersonic Boundary Layer on a Wall with Resonating Micro-Cavities. In: 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 4-7 January 2011, Orlando, FL.

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Ultrasonically absorptive coatings (UAC) can stabilize the Mack second mode and thereby increase the laminar run on configurations where laminar-turbulent transition is second-mode dominated. Theory indicates that the stabilization effect can be essentially enhanced by increasing the UAC porosity. However, direct numerical simulations (DNS) showed that coatings having closely spaced grooves can trigger a new instability whose growth rate can be larger than that of Mack' second mode. The nature of the new instability is investigated theoretically and numerically. 2D linear DNS and stability analysis are performed for the temporally evolving boundary layer on a flat wall at the outer-flow Mach number 6. The wall is covered by UAC comprising equally-spaced spanwise grooves. It is shown that the new mode is associated with acoustic resonances in the grooves. Disturbance fields near mouths of resonating cavities are coupled such that the boundary-layer disturbance is decelerated and becomes unstable. To avoid this detrimental effect the coating should have sufficiently small porosity and/or narrow pores of sufficiently small aspect ratio. Restrictions on these parameters can be estimated using the linear stability theory with the impedance boundary conditions.

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:© 2011 by Alexander V. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Published Online: 14 Jun 2012. This work is supported partially (Fedorov) by the AFOSR/NASA National Center for Hypersonic Research in Laminar-Turbulent Transition. Computer time was provided in part by the Department of Defense High Performance Computing centers.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Subject Keywords:Aerospace Systems, Operations and Life Cycle
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Other Numbering System NameOther Numbering System ID
AIAA Paper2011-373
Record Number:CaltechAUTHORS:20190717-102318931
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97200
Deposited By: Melissa Ray
Deposited On:18 Jul 2019 16:40
Last Modified:16 Nov 2021 17:29

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