TECHSPEC® Cr SERIES LENSES
Compact Ruggedized (Cr) for Shock and Vibration
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surface for analysis.
Previously, most insect studies modeled
the wing of insects as a fat surface. However, by ftting cubic splines to both the leading
and trailing edges of the wings, it is possible to calculate how the pitch angle of the
wing changed across its length, and from
that ascertain its importance in insect fight.
Many insects enhance lift production
through the creation of leading-edge vortices, which are rotational, bubbles of low
pressure created along the front edge of the
wing. These vortices create a pressure differential between the top and the underside of
the wing that produces additional lift. While
mosquitoes employ this technique, due to the
small angle through which they move their
wings, it was hypothesized that this could
only be one of the contributing factors which
enable them to fy. Indeed, the CFD simulation (Figure 3) revealed that the mosquitoes
employ two other additional novel aerodynamic mechanisms known as rotational drag
and trailing edge vortices.
Any wing or aerofoil that is at an angle relative to air produces both a lift force and a
drag force. The lift force perpendicular to the
oncoming airfow and the drag force is parallel
to it. While the lift force is generally considered to be advantageous and drag detrimental, if the drag is orientated upwards relative
to gravity, a force can still be created to support the bodyweight of an insect.
Indeed, the CFD analysis showed that the
mosquito makes use of the drag force to support its weight by changing the axis about
which its wings rotate during fight. Either
the wing can be rotated about the front (or
leading edge) of the wing, or it can be rotated about the rear (or trailing edge). By shifting the axis of rotation at specifc instances in
time, the drag force can then be directed so
that it contributes to supporting the weight of
the mosquito during fight.
In addition to making use of a drag force
to support their body weight, the analysis
also revealed that the mosquito also makes
use of trailing edge vortexes. These are akin
to leading edge vortexes, except that they
are generated on the rear, or trailing edge,
of the wing. By timing the rotational angle
and velocity of the wing, the trailing-edge
vortex is created on the upper surface of the
wing during an upstroke due to the capture
of the fow from the preceding down stroke.
This in turn creates a region of low pressure
on the upper portion of the wing which con-
tributes to the lift of the insect (Figure 4).
To verify the accuracy of the CFD model,
a Particle Image Velocimetry (PIV) system
was deployed to calculate the speed and di-
rection of fow around the wings of tethered
mosquitoes in the center of the fight cham-
ber. In the PIV experiments, the fight cham-
ber was seeded with a mist of olive oil drop-
lets which were illuminated with a sheet of