The pressure drag of
blunt bluff bodies
is highly relevant in many practical ap-
plications, including to the aerodynamic drag of road vehic
les. This paper presents theory
revealing that a mean drag reduction can be achieved by manip
ulating wake flow fluctu-
ations. A linear feedback control strategy then exploits th
is idea, targeting attenuation of
the spatially integrated base (back face) pressure fluctuat
ions. Large eddy simulations of
the flow over a D-shaped blunt bluff body are used as a test-bed
for this control strategy.
The flow response to synthetic jet actuation is characterise
d using system identification, and
controller design is via shaping of the frequency response t
o achieve fluctuation attenua-
tion. The designed controller successfully attenuates int
egrated base pressure fluctuations,
increasing the time-averaged pressure on the body base by 38
%. The effect on the flow-
field is to push the roll-up of vortices further downstream an
d increase the extent of the
recirculation bubble. This control approach uses only body
-mounted sensing/actuation and
input-output model identification, meaning that it could be
applied experimentally.