<DOC>
<DOCNO>
799
</DOCNO>
<TITLE>
some effects of wind-tunnel interference observed in tests on twodimensional
aerofoils at high subsonic and transonic speeds .
</TITLE>
<AUTHOR>
pearcey, h.h., sinnott, c.s. and osborne, j.
</AUTHOR>
<BIBLIO>
n.p.l. aero. 373. february 1959 .
</BIBLIO>
<TEXT>
in the high-speed research on two-dimensional aerofoils at the national
physical laboratory the need to keep model size above a certain minimum,
 in order to reproduce correctly the boundary layer separation effects
experienced at full scale, has been considered paramount even at the
risk of incurring significant tunnel interference effects .
this report discusses the interference effects for the slotted working
sections now in use . the magnitudes of the blockage and lift effect
corrections are deduced for the ratio of model chord to tunnel height
normally used . it is shown that a simple adaptation to reduce the open
area of the walls would reduce both corrections to insignificant proportions
simultaneously, but would give a reduced choking mach number
separated flows . the observed trends in the variation of the blockage
effects for other ratios of model chord to tunnel height differ from
those predicted theoretically, and so the results cannot be applied more
 generally until these trends have been checked by further investigations
.
it is suggested that wake interference effects can significantly influence
the manner in which separated flows develop with increasing
incidence or mach number, particularly for walls of small open area .
examples are also given of effects of distortions in the local supersonic
flow, which are most noticeable for walls with relatively large
open areas .
</TEXT>
</DOC>
