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National Advisory Committee for Aeronautics, Technical Notes - The Interference Effects on an Airfoil of a Flat Plate at Mid-Span Position

The report gives the results of an investigation of
the mutual interference of an airfoil and a flat plate in—
serted at.mid~span position The tests were conducted
in the Variable-Density Wind Tunnel of the National Advi-
sory Committee for Aeronautics at a high value of the Reyn—
olds Number. The interference effects.of.this‘combina—
tion were found to be small. Supplementary tests indicat—
ed-that the use of fillets decreases both the lift and H
drag,slightlys. A bibliography of publicatiOne dealing
with interference between wings and bodies. and with the
effects of cut-outs and fillets is included.

The trend toward higher speeds in aircraft has made
increasingly important the subject of mutual interfer—
ence of airplane parts. A bibliography dealing with the
interference between wings and bodies. and with the eff
facts-of cut~out3'and fillets is included in this report
for convenience of reference. Most of the information
included in the bibliography, however, is unrelated and
unsystematic and has been obtained from tests of models
at low values ef-the Reynolds Number. Therefore, much ,
of it is unsuitable for design use. The Variable-Density
Wind Tunnel of. the National Advisory Committee for Aero—
nautics affords a means of studying interference effects
with models at large values of the Reynolds Number. the
results of-which-may be compared directly'to the effects
which may be expected in the full-sized aircraft. A
preliminary investigation of the interference effects of
struts was recently.made in this'tunnel.' (Reference 1.)

The first step in amprogressive;sthdy of interfer—
ence would be an investigation of— th,e interference ef—
facts as shown upon basic forms at high values of the z
Reynolds Number. .As a part of such' .an investigation,
tests were cenducted in the Variable—Density—Wind Tunnel
in June, 1931. upon a symmetrical airfoil having a flat
plate inserted at "mid—span position.

The interference effects were determined from tests _._U
of the airfoil and the interference plate, separately and
in combination. Tests were also made with se_veral sizes
of fillets placed at the intersections between the plate
and the airfoil surfaces to determine whether the us-e of
fillets was effective in reducing adverse interference.