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Application of sound and temperature to control boundary-layer transitionThe growth and decay of a wave packet convecting in a boundary layer over a concave-convex surface and its active control by localized surface heating are studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiations are computed using linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. It is shown that on the concave portion the amplitude of the wave packet increases and its bandwidth broadens while on the convex portion some of the components in the packet are stabilized. The pressure field decays exponentially away from the surface and then algebraically, exhibiting a decay characteristic of acoustic waves in two dimensions. The far-field acoustic behavior exhibits a super-directivity type of behavior with a beaming downstream. Active control by surface heating is shown to reduce the growth of the wave packet but have little effect on acoustic far field behavior for the cases considered. Active control by sound emanating from the surface of an airfoil in the vicinity of the leading edge is experimentally investigated. The purpose is to control the separated region at high angles of attack. The results show that injection of sound at shedding frequency of the flow is effective in an increase of lift and reduction of drag.
Document ID
19900003221
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Maestrello, Lucio (NASA Langley Research Center Hampton, VA., United States)
Parikh, Paresh (NASA Langley Research Center Hampton, VA., United States)
Bayliss, A. (Northwestern Univ. Evanston, IL., United States)
Huang, L. S. (NASA Langley Research Center Hampton, VA., United States)
Bryant, T. D. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 6, 2013
Publication Date
December 1, 1987
Publication Information
Publication: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2
Subject Category
Aerodynamics
Accession Number
90N12537
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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