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National Advisory Committee for Aeronautics, Technical Notes - Investigation of Distributed Surface Roughness on a Body of Revolution at a Mach Number of 1.61

An investigation has been made of the effects of distributed sur-
face roughness, consisting of lathe—tool marks, on the skin—friction
drag of a body of revolution at a Mach number of 1.61. The tests were
made on ogive-cylinders at zero angle of attack over a roughness range
from 23 to #80 microinches root mean square and over a Reynolds number
range from 2.5 X 106 to 57 X 106.

The results indicate that the effects of surface roughness at a
Mach number of 1.61 are generally similar to those found at subsonic
speeds. Both the allowable roughness height for a turbulent boundary
layer and the variation with Reynolds number of the increment in skin—
friction drag due to roughness are in good agreement with Nikuradse's
lOthpeed data. At constant velocity, the allowable roughness height
is nearly independent of model length and dependent primarily upon
changes in Reynolds number per foot. As an approximation, in inches
root mean square,

An increase in surface roughness caused a small decrease in the
Reynolds number for transition at the model base for the ogive-cylinders
tested and had little or no effect on surface-temperature—recovery fac—
tors for the laminar or turbulent boundary layers. Pressure gradients
or body shapes apparently have little or no effect on the average skin-
friction drag coefficient for smooth bodies of high fineness ratio when
the boundary layer is turbulent.

The basic laws of skin friction on rough surfaces were established
by Nikuradse about 1955 by means of tests of rough pipes with water.
These results are translated in reference 1. Shortly thereafter,
Prandtl and Schlichting (ref. 2) showed how the pipe results could be
applied to a flat plate. This information, however, found little prac—
tical use in aeronautics at that time because the airplanes of that
date had very high form drag and relatively low maximum speeds and
these factors precluded any sizable effects due to surface roughness.