<DOC>
<DOCNO>
189
</DOCNO>
<TITLE>
experimental investigation of base pressure on blunt-trailing-edge
wings of supersonic velocities .
</TITLE>
<AUTHOR>
chapman,d.r., wimbrow,w.r. and kester,r.h.
</AUTHOR>
<BIBLIO>
naca r1109.
</BIBLIO>
<TEXT>
  measurements of base pressure are presented for 29 blunttrailing-edge
wings having an aspect ratio of 3.0 and various
airfoil profiles .  the different profiles comprised thickness
ratios between 0.05 and 0.10, boattail angles between --2.9
and 20, and ratios of trailing-edge thickness to airfoil thickness
between 0.2 and 1.0 .  the tests were conducted at mach numbers
of 1.25, 1.5, 2.0, and 3.1 .  for each mach number, the reynolds
number and angle of attack were varied .  the lowest reynolds
number investigated was 0.2 x 10 and the highest was 3.5 x 10 .
measurements on each wing were obtained separately with
turbulent flow and laminar flow in the boundary layer .  spanwise
surveys of the base pressure were conducted on several
wings .
  the results with turbulent boundary-layer flow showed only
small effects on base pressure of variations in reynolds number,
airfoil profile shape, boattail angle, and angle of attack .  the
principal variable affecting the base pressure for turbulent flow
was the mach number .  at the highest mach number investigated
(3.1), the ratio of boundary-layer thickness to trailingedge
thickness also affected the base pressure significantly .
  the results obtained with laminar boundary-layer flow to
the trailing edge showed that the effect of reynolds number on
base pressure was large .  in all but a few exceptional cases
the effects on base pressure of variations in angle of attack and
in profile shape upstream of the base were appreciable though
not large .  the principal variable affecting the base pressure
for laminar flow was the ratio of boundary-layer thickness to
trailing-edge thickness .
  for a few exceptional cases involving laminar flow to the
trailing edge, the effects on base pressure of variations in profile
shape, boattail angle, and angle of attack were found to be
unusually large .  in such cases the variation of base pressure
with angle of attack was discontinuous and exhibited a hysteresis
.  stroboscopic schlieren observations at a mach number
of 1.5 indicated that these apparently special phenomena were
associated with a vortex trail of relatively high frequency .
</TEXT>
</DOC>
