<DOC>
<DOCNO>
416
</DOCNO>
<TITLE>
methods of boundary-layer control for postponing and alleviating
buffeting and other effects of shock-induced separation .
</TITLE>
<AUTHOR>
pearcey, h.h. and stuart, c.m.
</AUTHOR>
<BIBLIO>
smf fund paper, no. f.f. -dash 22, 1959 .
</BIBLIO>
<TEXT>
the use of boundary-layer control to increase the separation-free
margins of mach number and lift coefficient beyond the cruise point of
high-speed aircraft may often be preferred to design changes that impair
 the cruising performance or the landing and take-off characteristics .
the factors that influence the choice of method and details of its application
are discussed, emphasising particularly the need to maintain
effectiveness over most of the chord to cover the wide range of separation
positions encountered as the shock moves over the wing with changing
flight conditions .
research at the national physical laboratory that has embraced highvelocity
blowing, vane and air-jet vortex generators, and, in a
preliminary way, distributed suction, is briefly described . the
relative merits of the various methods are discussed, and some results
achieved in their application are given .
for vortex generators, the importance is stressed of the vortex paths
determined by the interactions of neighbouring vortices and their
images . thus, systems of counter-rotating vortices always leave the
surface in pairs and lose their effectiveness . co-rotating systems are
therefore preferred for many applications . blowing, which in windtunnel
tests gives results as good as or better than vortex generators
and does not have the disadvantage of a drag penalty at cruise, has not
yet been assessed in flight . air-jet vortex generators, which would
also avoid the drag penalty, show promise of producing significant
effects with relatively small blowing pressures and quantities .
</TEXT>
</DOC>
