Abstract:
Pressure distributions have been measured over
the surface of a N.A.C.A. 63A215 aerofoil section to
determine the effect of transition wires on the lift
and pitching moment characteristics. These tests,
which were made at Reynolds numbers of 3 x 10-) and
8 x 10J, showed that with transition left free laminar
separation, followed by turbulent re-attachment,
occurred at about 604 chord at low incidences. At
medium incidence the position of laminar separation
and turbulent re-attachment moved rapidly forward
giving rise to kinks or non-linearities in the lift
curve.
The addition of transition wires at 271% chord
eliminated the laminar separation at low incidences
and thereby caused the lift curve to become more nearly
linear. However, the wires resulted in a reduction in
the lift-curve slope at the design CL, and a reduction
in Climax.
Transition wires at 8%, /a or 1% chord were found
to have very adverse effects on the aerofoil characteristics.
In particular the lift curves were made very non-linear,
and CL max was reduced. The non-linearity was caused by
sudden changes in the boundary layer with change of incidence.
