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National Advisory Committee for Aeronautics, Report - A Comparison of the Experimental Subsonic Pressure Distributions about Several Bodies of Revolution with Pressure Distributions Computed by Means of the Linearized Theory

An analysis is made of the ejects of compressibility on the
pressure coeflicients about several bodies of revolution by com-
paring erperimentally determined pressure coeficients with
corresponding pressure coeficients calculated by the use of the
linearized equations of compressible flow. The results show
that the theoretical methods predict the subsonic pressure-
coefiment changes over the central part of the body but do not
predict the pressure-coeficient changes near the nose. Ea:-
trapolation of the linearized subsonic theory into the mixed
subsonie-supersonic flow region fails to predict a rearward
movement of the negative pressure-coefi'icient peak which occurs
after the critical stream Mach number has been attained. Two
equations developed from a consideration of the subsonic com-
pressible flow about a prolate spheroid are shown to predict,
approccimately, the change with Mach number of the subsonic
pressure coefiicients for regular bodies of revolution of fineness
ratio 6 or greater.

A number of papers have been published concerning the
theoretical aspect of the effects of compressibility on the
flow over bodies of revolution (refs. 1 to 4). In the present
investigation these theoretical methods are applied to the
analysis of experimental data. Such an analysis should
contribute to the basic knowledge of subsonic three-
dimensional flow.

Two prolate spheroids of fineness ratios 6 and 10, an ogival
body, and a prolate spheroid with an annular bump near the
nose were tested in this investigation; The experimental
pressures about the two prolate spheroids are compared with
the pressures computed by the linearized compressible-flow
theory. Several relations developed from theoretical con-
siderations of the flow about a prolate spheroid are presented
for correcting the incompressible pressure coefficients of
regular bodies of finances ratios 6 to 10 for the effects of
compressibility in- the subcritical flow range. Results
obtained from these relations are also compared with corre-
sponding experimental pressure coefficients.