Abstract:
The interaction of the vortex and the flexible flag in wake of a bluff body is a
common occurrence in nature and in engineering fields. The limited availability and
the environmental impact of fossil fuels motivate the development of renewable
energy sources. Considerable efforts are focused on use of renewable energy from
natural resources such as flowing water, rain, tides, wind, sunlight, geothermal heat
and biomass. Renewable energy from small-scale hydro, modern biomass, wind,
solar, geothermal and biofuels accounted for global energy consumption was 2.7% in
2008, increased to 5.8% in 2012 and is growing very rapidly.
Aquatic animals utilize oscillatory motions of the fins or wings to achieve propulsion
and maneuvering. They extract energy from the incoming vortices or unsteady flows.
Zhu et al. showed that the caudal fin of a fish can absorb energy from vortices shed
from the dorsal fins to increase the propulsion efficiency. Also dead fish is capable of
moving upstream within the Karman vortex street generated by a D-shape cylinder.
Bio-inspired energy harvesting devices based on the oscillatory motions of foils had
been developed by using an oscillating wing to extract energy from the unsteady flow
fields generated by the free-surface waves. The application of flapping wings to
extract energy from uniform flows was first proposed by McKinney and De Laurier.
Both experiments and theoretical analyses discovered that a foil submerged in the free
surface could propel by using the energy from the incoming waves. With the growing
importance of renewable energy, the interest in this novel concept has been rekindled
in the past few years. Allen and Smits examined the response of the piezoelectric
membrane to vortex shedding Introduction.
