To increase the flight endurance of a Micro air vehicle (MAVs), which operates at low Reynolds number flow, one way is to harvest energy during its flight. By inspiring from the nature when all the birds use their feathers to control and distribute their power along the flying time, a solution might be design of a piezoelectric plate as feathers, which scavenges energy directly from the fluid flow. Cantilevered beam with piezo-ceramic layer undergoing vortex-induced vibrations can convert the mechanical energy available from the ambient environment to a usable electrical power. Since a flow-driven piezoelectric composite beam takes a form of natural three-way coupling of the turbulent fluid flow, electrical circuit and structural behavior of the beam, the difficulties of modeling and simulations would be sharply increased. Also there are a lot of parameters, which effect on the performance of active feather such as its length. Therefore, effect of its length are studied and several feathers with different lengths are numerically examined.

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