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My
earlier research work (PhD thesis) involved using
active and passive
methods for flow control in various S-duct diffuser
configurations.
S-duct diffusers are used in air intakes of combat
aircraft to provide
requisite quantity of good "quality" of air
throughout the flight
envelope. Space and weight constraints causes
increased curvatures and
divergence angles in these diffusers resulting in
secondary flows and flow separation. The
"quality" of air flow is measured in terms of the
total pressure
recovery and distortion. Ideally one would have
liked to have an air
intake with no total pressure losses and
circumferential distortion. A
poorly performing air intakes adversely affects the
engine operation.
Improving the air intake performance is hence very
important for
efficient operation of the engine.
Active and passive control methods were used for
performance
enhancement of S-duct diffusers. The active flow
control method used
was Vortex
Generator Jets (VGJ) that involves
injecting air at various
pitch and skew angles with reference to the
freestream. Vortices are
generated due to the jet-crossflow interaction.
The strength and
orientation of the vortices can be suitably
adjusted as required by the
application. Tapered-fin vortex generators were
the passive flow
control method used. The orientation angle of
these devices were also
varied to achieve best performance. Details
of these methods can
be found in some of my earlier publications.
I also
have interests in developing new measurement methods,
flow visualization tools etc. Smoke and surface
oil-flow visualization
were
used to study the mechanism of flow control by
tapered-fin vortex
generators and vortex generator jets. Shear-sensitive liquid
crystals were used for measuring the wall shear
stress distribution in internal as well as external flow
applications.
An LVDT based wall
shear stress sensor was designed and developed for
the purpose of calibrating other measurement
methods like Preston
tubes, sublayer fences and shear sensitive liquid
crystals.
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