Reduction of wave drag of wing-body combinations at supersonic speeds through body distortions Page: 2 of 10
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TECH LIBRARY KAFB, NM
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NACA RM A56B10 0143515
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
REDUCTION OF WAVE DRAG OF WING-BODY COMBINATIONS AT
SUPERSONIC SPEEDS THROUGH BODY DISTORTIONS
By William C. Pitts
The word "interference" is usually associated with adverse effects.
However, interference between the components of an airplane or missile
can also be beneficial. The methods of drag reduction by body distortion
are examples. Figure 1 shos a simplified picture of the mechanics of
this beneficial interference. A wing with a biconvex section is mounted
on a cylindrical body. The dashed curve represents a body distortion
which produces a drag-reducing interference. This distortion creates a
negative pressure region to relieve the compression of the air on the
forward part of the wing, and it creates a positive pressure region to
compensate for the expansion of the air flowing over the after part of the
wing. The problem to be solved by all the drag-minimization theories is
to determine the magnitude and shape of this distortion that will reduce
the wave drag on the wing as much as possible without unduly increasing
the body drag.
There are several methods for doing this. The original method is
the transonic area rule, which is limited to Mach numbers near unity.
The so-called supersonic area rule is limited to slender configurations.
Separate linear-theory investigations have been made by Lomax and Heaslet
(ref. 1) and by Nielsen (ref. 2) to study the problem of drag minimiza-
tion outside the region of applicability of these rules. This paper will
discuss the theoretical bases of the theories of references 1 and 2 and
present experimental results. A method recently investigated at the
Langley Aeronautical Laboratory will also be discussed.
In reference 1 the problem of drag minimization is solved without
recourse to body boundary conditions. Rather than treating actual shapes,
the theory deals with multipole distributions along the body axis to find
the minimum condition. Then the body shape is found from the resulting
multipole distribution as the last step. The resulting body contains two
types of distortion. One type is the axisymmetric distortion due to the
sources. The other type is the nonaxisymmetric distortion due to higher
order mltipoles. Figure 2 shows the experimental verification of the
ability of these distortions to produce drag reductions. The theory was
applied to a wing of elliptic plan form for a design Mach number of (.
The body contained both axisymmetric and nonaxisymmetric distortions.
Transition was fixed to minimize change in viscous effects. The quan-
tity tCD is the drag with the distorted body minus the drag with the
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Pitts, William C. Reduction of wave drag of wing-body combinations at supersonic speeds through body distortions, report, April 13, 1956; (digital.library.unt.edu/ark:/67531/metadc62821/m1/2/: accessed November 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.