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National Advisory Committee for Aeronautics, Report - Experimental Investigation of the Effects of Viscosity on the Drag and Base Pressure of Bodies of Revolution at a Mach Number of 1.5

Tests were conducted to determine the ejects of viscosity on
the drag and- base pressure of carious bodies of‘recolution at a
JIach number of 1.5. The models were tested both with smooth
surfaces and with roughness added to ecaluate the ejects of
Reynolds number for both laminar and turbulent boundary
layers. The principal geometric cariables inrestigated were
afierbod-y shape and length-diameter ratio. For most models,
force tests and base pressure measurements were made over a
range of Reynolds numbers, based on model length, from
0.6 X 10“ to 5.0X10°.' Schlieren photographs were used to
analyze the ejects of oiscosity on flow separation and shock-
u'ace configuration near the base and to cerify the condition of
the boundary layer as deduced from force tests. The results
are discussed and compared with theoretical calculations.

The results show that viscosity efects are. large and depend
to a great degree on the body shape. The ejects difl’er greatly
for laminar and turbulent flow in the boundary layer, and
within each regime depend upon the Reynolds number of the
flow. Laminar flow was found up to a Reynolds number of
6.5 X10“ and may possibly exist to higher calues.

{The flow over the afterbody and the shock-wow configuration
near the base are shown to be very much dwerent for laminar
than forturbulentflowin the boundary layer. The base pressure
on bodies with boattailing is much higher with the turbulent
layer than with the laminar layer, resulting in a negatice base
drag in some cases. The total drag charactefistics at a given
Reynolds number are afiected considerably by the transition to
turbulent flow. The foredrag of bodies without boattailing and
of boattailed bodies for which the ejects offlow separation are
negligible can be calculated with reasonable accuracy by adding
the slain-friction drag based upon the assumption of the low—
speed friction characteristics to the theoretical ware drag.