<DOC>
<DOCNO>
686
</DOCNO>
<TITLE>
flutter tests of some simple models at a mach number
of 7. 2 in helium flow .
</TITLE>
<AUTHOR>
morgan,h.g. and miller,r.w.
</AUTHOR>
<BIBLIO>
nasa memo 4-8-59l, 1959.
</BIBLIO>
<TEXT>
  results of hypersonic flutter
tests on some simple models are presented
.  the models had rectangular
plan forms of panel aspect ratio 1.0,
no sweepback, and bending-to-torsion
frequency ratios of about .  two
airfoil sections were included in the
tests ,. double wedges of 5-, 10-,
and 15-percent thickness and flat plates
with straight, parallel sides
and beveled leading and trailing edges .
the models were supported by a
cantilevered shaft .
  the double-wedge wings were tested
in helium at a mach number of 7.2 .
an effect of airfoil thickness on flutter
speed was found, thicker wings
requiring more stiffness to avoid flutter .
a few tests in air at a mach
number of 6.9 showed the same thickness
effect and also indicated that
tests in helium would predict conservative
flutter boundaries in air .
the data in air and helium seemed to be
correlated by piston-theory calculations
.  piston-theory calculations
agreed well with experiment for
the thinner models but began to deviate
as the thickness parameter
approached and exceeded 1.0 .
  a few tests on flat-plate models
with various elastic-axis locations
were made .  piston-theory calculations
would not satisfactorily predict
the flutter of these models, probably
because of their blunt leading
edges .
</TEXT>
</DOC>
