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N. Chari and P. Srinivas

The detailed study of these mechanisms might help in the design of improved

wings for bio-mimicking MAVs operating at low Reynolds number.

Ravi [43] in his thesis has studied the aerodynamic parameters and power require-

ments of a pentatomid bug in detail. Vydehi [44] has elucidated the unique flight

features of a soapnut bug. Vydehi in her thesis and subsequent publications included

the basic and derived parameters and their significance in the study of insect

flight. Dickinson et al. [45] explained three main principles to explain insect flight

effectively viz.,

a.

Specific kinematics of wing motion during flapping and rotation

b.

Ability to delay flow separation from the wing

c.

Using the energy of vortex wake.

Significant factors in the study of the aerodynamics of insect flight have been

reviewed by Sane [46]. This inspires in developing bio-inspired MAVs and flapping

wings as prototypes. Shyy et al. [47] discussed elaborately and summarized recent

progress in flapping wing aerodynamics and aeroelasticity at low Re. MAVs have the

potential to revolutionize sensing and information gathering, such as environmental

monitoring and homeland security as and when required. They also considered the

role of spanwise flexibility in the forward flight which influences shape deformation

and also the effective change of angle of attack along the wingspan.

Insect flight due to flapping of wings mostly depends on structural deformations

influenced by aeroelastic properties. This knowledge in turn could help in a better

understanding and possible design of flapping flexible wings.

The present review covers “the basic principles underlying flapping flight in

insects, results of recent experiments concerning the aerodynamics of insect flight,

as well as the different approaches used to model these phenomena”.

Recent Findings

The concluding remarks of Shyy et al. [47] based on Aerodynamics of Low Re fliers

can be summarized as follows:

1.

They have discussed various low Re fliers, flight characteristics and scaling laws

related to wingspan, wing area, wing loading and body parameters.

2.

The lift to drag ratio of a flier decreases as Re drops 10⁴. A corrugated dragonfly

wing exhibiting anisotropic properties can develop favourable lift as compared

to a non-corrugated wing surface because of viscous effects. Wind gusts play

an important role in low Re fliers having low mass. The tip vortex induces a

downwash effect for a low Aspect Ratio (AR) and low Re fliers. The wingtip

vortices reduce the lift force.

3.

For the design of flapping wing MAVs, an understanding of kinematics, vortex

structures and Reynolds number are essential. When we think of MAV design

based on insect flight, the considerations of moderate frequency, multi-scale