Preliminary investigation of effectiveness of base bleed in reducing drag of blunt-base bodies in supersonic stream Page: 3 of 26
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NACA RM E51A26U
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
PRELIMINARY INVESTIGATION OF EFFECTIVENESS OF BASE
BLEED IN REDUCING DRAG OF BLUNT-BASE
BODIES IN SUPERSONIC STREAM
By Edgar M. Cortright, Jr. and Albert H. Schroeder
The drag-reducing effectiveness of bleeding air to the base
region of blunt-base bodies in a supersonic stream was investigated
at a Mach number of 1.91. The first phase of the study consisted
of base-pressure measurements on bodies of revolution with both a
cylindrical afterbody and with conical boattails. In this phase,
variable base bleed was provided from an external air supply.
Base bleed was shown to be an effective means of reducing the
base pressure drag. Increases in base-pressure coefficient of
0.04 were obtained with the cylindrical-afterbody configuration.
The variation of base pressure with quantity of base bleed was
such that bleed-air sources at ambient pressure or less could be
The second phase of the investigation employed force measure-
ments to determine whether drag reductions could be obtained under
practical conditions of bleed air intake. Simple drilled holes
in the cylindrical portion of a hollow cone-cylinder body of
revolution with open base resulted in total drag coefficient
reductions of 0.03. Bleed air intake through the nose resulted
in only slight net-drag reductions.
When bodies with blunt bases are submerged in a supersonic
stream, the external air flow separates from the bodies at the bases.
This separation results in a semidead air region at the base that
is generally at a lower pressure than the ambient fluid. The
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Cortright, Edgar M., Jr. & Schroeder, Albert H. Preliminary investigation of effectiveness of base bleed in reducing drag of blunt-base bodies in supersonic stream, report, March 9, 1951; (digital.library.unt.edu/ark:/67531/metadc58881/m1/3/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.