|
Insect wings consist of flat plates of membranes stiffened by spars. The effect of this structure
is that the wings appear as corrugated surfaces when considered on chordwise sections. We
know that aerodynamically efficient insects such as a dragonfly engage in fixed wing flight modes
for extended periods. The analysis in the literature has shown that the aerodynamic efficiency
(cl/cd) of a corrugated aerofoil is sensitive to Reynolds number (Re) and angle-of-attack (AoA), yet the conclusions established are on the basis of flow analysis on a single baseline shape only.
The sample size of the aerofoils must be extended further so that the influence and merits
of corrugated shape features can be established. In this work, a design-of-experiments (DoE)
approach is applied to induce systematic shape perturbations on a select, off-the-shelf baseline
shape one feature at a time over a set number of increments. At each shape increment, the
aerodynamic forces are established using a high fidelity CFD solver. The design space is modeled
at a Re of 20,000 and 34,000 and at flow angle of 4.0° to represent a Micro Air Vehicle (MAV) in
glide. The results confirmed the importance of the leading and trailing edge deflections on cl/cd.
At Re = 20, 000, cl/cd of a corrugated aerofoil with deflection at the leading edge region only is
16% higher than the baseline shape, and 39% higher than the flat plate. At Re = 34, 000, cl/cd
performance is sensitive to the trailing edge deflection. At the optimum deflection setting, cl/cd
is 18% higher than the baseline shape and 23% higher than the flat plate. The results confirm
that the leading and trailing edge deflections are critical to cl/cd for a MAV in glide.
|
