VIVACE-W is a fish-friendly device that can extract energy from currents and/or waves using the same physical components. It consists of 3-4 horizontal cylinders on elastic restraints designed with variable stiffness so they are in resonance with waves and/or currents. VIVACE-W uses fish-school biomimetics to generate energy from currents. Decades of studies have established that fish thrive in the alternating wakes of cylinders. VIVACE-W is acceptable to communities because: (a) its parts move only about 20-40% faster than the flow, presenting no danger, making no noise, and providing a thriving shelter to fish, and (b) is visually unobtrusive as it remains fully submerged.
Fish propel efficiently using effective undulation shapes and alternating lift, not steady lift like propellers. In schools, fish move synergistically utilizing the surrounding alternating wakes.
Underlying Physics: Elastic, elongated bodies, such as cylinders or prisms on springs, undergo fluid structure interaction in the form of flow induced oscillations (FIOs). FIOs, primarily vortex induced vibrations (VIV) and galloping, involve alternating lift and nonlinear resonance. Geometry is simple but dynamics is very complex involving interaction between boundary layers, separation points, shear layers, von Kármán vortices, vortical wakes, and oscillating bodies. As stiffness, damping, mass, spacing, and flow speed change, numerous bifurcations occur resulting in different interaction phenomena with oscillatory modes ranging from high to small energy harvesting. The former result when the cylinder oscillation patterns match fish undulation shapes.
2nd Generation Design: The underlying phenomena used by VICACE-W are highly scalable enabling design of converters from portable to local grid to utility grid sizes. It consists of seven subsystems as follows.
Hydrodynamics: Nonlinear resonance of VIV or galloping instability result in alternating lift and oscillatory motion of cylinders. Close proximity of properly designed cylinders results in synergistic FIOs with higher MHK conversion than isolated cylinders. Interaction phenomena are numerous and hard to identify as the number of cylinders increases.
Turbulence Stimulation: Is a key subsystem which enables: (a) Early onset of FIO at flow velocities as low as 0.19m/s (0.4knots). (b) Synergy between cylinders. (c) Open-ended, high-response, Response Amplitude Operator.
Control: Instead of controlling the system response (displacement) to force improved energy harvesting – which potentially would interfere and break down the FIO driving mechanism – we control the oscillator properties to enable the system to adapt and precipitate into high energy harvesting oscillatory patterns. Specifically, in real-time: (a) The natural period of the cylinders is adjusted so that power extraction from currents and/or waves is maximized. (b) The damping is adjusted to harness energy from higher energy oscillations inducing patterns similar to fish-undulation.
It should be noted that the fluid-structure interaction between multiple oscillating cylinders in interactive FIOs, bifurcate in numerous ways depending on the system parameters. Developing dense enough experimental and/or CFD database for numerical modeling is prohibitive.
Magnetic restraints: Provide “levitation” against the hydrodynamic drag and contactless restraint for zero friction.
Magnetic gear: Enables creating a dry environment for controller, amplifier and power electronics.
Power electronics: Includes conditioning the raw electrical signal and charging a battery or powering a consumer.
Supporting frame: In the portable scale, it is designed to be easily deployable holding 3-4 oscillators.
Conclusion: VIVACE-W is designed to mimic fish-dynamics without the complexity of fish-kinematics.