<DOC>
<DOCNO>
272
</DOCNO>
<TITLE>
oscillatory aerodynamic coefficients for a unified supersonic
hypersonic strip theory .
</TITLE>
<AUTHOR>
rodden, w. +. and revell, j.d.
</AUTHOR>
<BIBLIO>
j. ae. scs. 1960, 451.
</BIBLIO>
<TEXT>
  the shock tube is shown to be a feasible research tool for conducting
boundary-layer transition experiments .  the use of the
shock tube permits the study of transition with highly cooled
boundary layers, as may be encountered on hypersonic vehicles .
  boundary-layer transition investigations have been made on
optically polished pyrex hemisphere-cylinder and ellipse-cylinder
models with stagnation-to-wall enthalpy ratios between 4.5 and
roughness estimated to be less than 1 microinch (rms) .  transition
was detected by measurements of the heat-transfer rates on
the model surface .
  the shock tube experiments indicated that a characteristic
feature of transition of a highly cooled boundary layer on a hemisphere
was the simultaneous occurrence of transition over the
entire supersonic portion of the hemisphere .  this implies that
transition first occurred in the sonic region .  the transition
reynolds number (based on local fluid properties at the outer
edge of the boundary layer and the momentum thickness) in the
sonic region increased from about 225 to 325 as the stagnation-towall
enthalpy ratio increased from about 9.5 to 29.5 .  transition
occurred along the cylindrical portion of the hemisphere-cylinder
model at a nearly constant momentum thickness reynolds
number, increasing from about 400 to 625 as the stagnation-towall
enthalpy ratio increased from about 9.5 to 29.5 .
  the highly cooled boundary layers obtained on the cylindrical
portion of the shock tube hemisphere-cylinder model provided an
extension of nasa transition results obtained on a cooled hemisphere-cone-cylinder
model in a wind tunnel .  the transition
reynolds numbers obtained from these shock tube data were of
the same order of magnitude as the minimum transition reynolds
numbers obtained in the wind-tunnel experiments .  the
results indicate that, for practical purposes, boundary-layer
cooling is not a critical transition parameter for blunt bodies with
a highly cooled boundary layer resulting from a stagnation-towall
enthalpy ratio of about 3 to 30 .  that is, the transition
reynolds number did not vary significantly with boundarylayer
cooling in this cooling range, but transition always occurred
at a low reynolds number (between about 350,000 and 750,000
based on local external properties and a distance along the body
surface from the stagnation point) .
  the boundary-layer history (body shape history) appeared to
be an important parameter affecting the magnitude of the reynolds
number for transition and the amount of increase in the
transition reynolds number with increased boundary-layer
cooling .  that is, transition occurred at a lower reynolds number
on the ellipse-cylinder configuration than on the hemispherecylinder
.  also, the increase in transition reynolds number with
an increase in boundary-layer cooling was even less significant
for the ellipse-cylinder than the hemisphere-cylinder .
</TEXT>
</DOC>
