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In order to operate a micro electromechanical device, we need a small amount of
energy. In this research, we suggested an energy harvesting system based on wake flow for
these types of devices. Energy harvesting using piezoelectric flag is a renewable energy
source which attain a lot of interest in the research field. The flag oscillates when the fluid
force at certain velocity strikes the bluff body. It is positioned at the wake of the cylinder, and
it functions as cantilever beam. When the water strikes the bluff body vortices is generated
which tend to oscillate the flag and energy is transferred. The kinetic energy of the fluid is
converted into electric energy using the piezoelectric flag and supplied directly to the small
sensors when needed. Cross section area of the cylinders and different parameters strongly
influenced on the power output. To investigate the impact of parameter on the energy
harvesting, a flexible flag is used.
Detail experimentation was performed to investigate the influence of parameter with
change in aspect ratio of cylinder on the power output. In this study, rectangular cylinder of
different aspect ratio (1, 1.2 and 1.4) with bio inspired fins (Dorsal, Pectoral and Pelvic) were
used. Apart from bluff body, other parameter like streamwise gap (Gx), stiffness of the flag
and velocity plays an Important role in the energy harvesting. Total 63 cases were performed
in our study and in each case 1 – 1.5min video was recorded to investigate the flapping of the
eel. Total nine different type of cylinders was used in our study on which experimentation
was done at different streamwise gaps. Streamwise gap (Gx) varies from 1 - 4. By varying the
Gx we have found out that at some position the coupling of the wake with the piezoelectric
flag is good enough and produce maximum strain.
The results concluded that by using Dorsal fins having 1.2 A.R rectangular cylinder
gives maximum power. Maximum power was achieved at Gx = 3.5 which is 82.74µW.
Minimum power was shown in 1 A.R rectangular cylinder in Dorsal fin at Gx = 1 which is
7.63µW. We had compared the hollow circular cylinder with our study, 5-10% more power
was harvested.