English abstract
This research focused on the design and dynamic modeling of a broadband electromagnetic
Vortex Bladeless Wind Turbine (VBWT) with a non-linear tuned mechanism. Two
progressive-rate springs are part of the tunable mechanism, which are connected to two
oscillating magnets inside an electromagnetic coil. The Vortex-Induced Vibration (VIV)
caused by the wind flow crossing over the oscillating mast is tuned to match the shedding
frequency by gradually adjusting the spring stiffness as the wind speed varies. Using the
lumped-mass model and Newton formulation, the coupled nonlinear equations of motion for
the tunable turbine are derived. The tunable bladeless turbine operates well at high average
wind speeds, as demonstrated by numerical data, without experiencing any structural failures
(i.e., good damping). The optimum turbine's mechanical fundamental frequency is expressed
analytically, with respect to the non-linear stiffnesses and displacement. The numerical
evaluations and the analytical results agree rather well. The output power of the tunable
turbine reaches its maximum value at a particular non-linear stiffness beyond the threshold.
Comparing the 2 m long tunable turbine to a typical bladeless turbine under identical
conditions and at higher wind speeds, numerical studies also demonstrate that the output
power of the former is superior. For instance, the output RMS power of the tunable turbine
is approximately 37.5 W at a wind speed of around 24 m/s, compared to almost zero watts
for the traditional VBWT. Strong winds cause a decoupling between the emergence of
vortices and the structural oscillation frequency in the case of traditional VIV resonant wind
turbines. As lift forces become less significant than drag forces, resonance and oscillation
vanish. An ideal external load can help increase the power even more. Conventional small
bladeless wind turbines violently oscillate at high wind speeds, which primarily results in
uncontrollable resonance and system failure. In contrast, tuned turbines effectively sustain
wind speeds beyond 20 m/s. This study proved the viability and benefits of the suggested
tuned mechanism to improve the bladeless wind turbine's overall performance at high wind
speeds, particularly in urban grounds like Oman (i.e., 16-31 m/s). To boost the harvester
output power and expand the bandwidth frequency, a subset of the geometrical parameters
of the suggested harvester are optimized using the fundamental Cat Swarm optimization
algorithm (CSO). It has been discovered that the recommended harvester's maximum power,
when operating at its third natural frequency, is roughly 37.5 W. This can be achieved by
optimizing the harvester's physical parameters using a variety of objectives or fitness
functions.
