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Unsteady Newton-Busemann flow theory. I - AirfoilsNewtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.
Document ID
19810041108
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Hui, W. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Tobak, M.
(NASA Ames Research Center Moffett Field, Calif., United States)
Date Acquired
August 11, 2013
Publication Date
March 1, 1981
Publication Information
Publication: AIAA Journal
Volume: 19
Subject Category
Aerodynamics
Accession Number
81A25512
Distribution Limits
Public
Copyright
Other

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