<DOC>
<DOCNO>
1212
</DOCNO>
<TITLE>
effect of uniformly distributed roughness on turbulent
skin-friction drag at supersonic speeds .
</TITLE>
<AUTHOR>
goddard,f.e.
</AUTHOR>
<BIBLIO>
j. ae. scs. 1959, 1.
</BIBLIO>
<TEXT>
  an experimental program was carried out in the 18-in. by 20in.
supersonic wind tunnel of the jet propulsion laboratory to
determine the effect of uniformly distributed sand-grain roughness
on the skin-friction drag of a body of revolution for the case
of a turbulent boundary layer .  the mach number range covered
was 1.98 to 4.54, and the reynolds number varied from
about 3 x 10 to 8 x 10 .  some data were also obtained at a
mach number of 0.70 .
  at speeds up to a mach number of 5 and for roughness sizes
such that the quadratic resistance law holds, the compressibility
effect is indirect, and the skin-friction drag is a function of only
the roughness reynolds number, exactly as in the incompressible
case .  it is shown that the entire compressibility effect
is a reduction of the fluid density at the surface as the mach
number increases .  the critical roughness, below which the
surface is hydraulically smooth, is,. this is equal
to the thickness of the laminar sublayer for a smooth surface for
both compressible and incompressible flow .  over the range of
roughness sizes considered here, there appears to be no wave drag
associated with the drag due to roughness .  the shift in the turbulent
veocity profile for a rough surface at supersonic
speeds is a function of only the roughness reynolds number
and quantitatively follows exactly the same law as that
for the incompressible case .
</TEXT>
</DOC>
