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Aeroelasticity

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2.

Structural deformations resulting due to the semi-elastic nature of the body

(wing) leading to the development of aerodynamic forces.

3.

The viscous effects of the fluid flow as it flows over the body.

4.

Boundary layer separations.

5.

The formations of the vortices and the associated lift, drag and thrust forces.

The subject of Aeroelasticity considers all aspects of the material, inertial and

structural interactions of an elastic body moving in a fluid stream.

The birds, insects and bats are natural fliers in contrast to man-made fliers such

as aeroplanes, missiles, helicopters, UAVs and MAVs. The natural fliers are capable

of flying in various environmental conditions such as gusts, heavy rains and may

be even in storms. They have cultivated the art of flying including forward flight,

hovering and various forms of gliding. In this process, the natural fliers can perform

various body and wing movements because they have relatively flexible bodies and

wings. The flapping of the wings in these natural fliers is considered to be a complex

motion, which includes sidewise, up and down as well as bending/twisting motions.

This can, in a way, be compared to the swimming carried out by aquatic animals. All

such actions of these natural fliers are possible due to the semi-elastic nature of the

wings, body and the fulcrum, associated with their structural deformations. On the

other hand, man-made fliers such as aeroplanes and helicopters using fixed or rotor

wings for their flight have limited capabilities and flexibility in wing movement.

Historical Background

In 1896, Samuel Langley was the first to design a flying bi-plane aircraft planned

to be launched by Catapult Mechanism. However, as soon as it took off, it had an

accident due to the twisting of the wings, and later on, it was attributed to aeroelastic

interactions. In 1903, Wright Brothers were able to fly another bi-plane at 30 mph.

This machine had light wings, a powered engine and two propellers. In 1905, they

built an improved aeroplane and flew a distance of twenty-four miles in thirty-eight

minutes. From 1930 onwards, only the monoplanes are flying and are popular as

compared to the bi-planes (A type of aeroplane having two sets of wings, one above

the other, where there is a lot of interference).

A definition for aeroelasticity is given by Arthur Roderick Collar in 1978 as

“the study of the mutual interactions that take place within the triangle of the iner-

tial, elastic, and aerodynamic forces acting on structural members exposed to an

airstream, and the influence of this study on design” [1].