Aerodynamics of bird and insect flight

In this article, the literature on the aerodynamics of bird and insect flight has been reviewed. Emphasis has been laid on the technological requirement of identifying a simple and suitable mechanism, which can be adopted for Micro Air Vehicle (MAV) applications. Large birds use steady aerodynamic principles for their flight, including gliding, soaring and dynamic soaring. Smaller birds and insects, however, use unsteady aerodynamic mechanisms like clap and fling mechanism, delayed stall and wing rotation, wake capturing and asymmetric flapping. The review presents salient features of these mechanisms and highlights the need to consider unsteady mechanisms for micro air vehicle applications. Unsteady mechanisms enable MAVs to hover and perform other maneuvers, which are not possible with fixed-wing, steady-aerodynamic mechanisms. Research is needed to measure all the components of forces and torques produced by a flapping test-rig, while 3-D numerical simulations may identify optimum wing-kinematics and flapping strategies for a given application. These studies will bring out the importance of individual mechanisms in unsteady aerodynamics.