Abstract
The generation of clean renewable energy is becoming increasingly critical, as pollution and global warming threaten the environment in which we live. While there are many different kinds of natural energy that can be harnessed, marine tidal energy offers reliability and predictability. However, harnessing energy from tidal flows is inherently difficult, due to the harsh environment. Current mechanisms used to harness tidal flows center around propeller-based solutions but are particularly prone to failure due to marine fouling from such as encrustations and seaweed entanglement and the corrosion that naturally occurs in sea water. In order to efficiently harness tidal flow energy in a cost-efficient manner, development of a mechanism that is inherently resistant to these harsh conditions is required. One such mechanism is a simple oscillatory-type mechanism based on robotic fish tail fin technology. This uses the physical phenomenon of vortex-induced oscillation, in which water currents flowing around an object induce transverse motion. We consider two specific types of oscillators, firstly a wing-type oscillator, in which the optimal elastic modulus is being sort. Secondly, the optimal selection of shape from 6 basic shapes for a reciprocating oscillating head-type oscillator. A numerical analysis tool for fluid structure-coupled problems—ANSYS—was used to select the optimum softness of material for the first type of oscillator and the best shape for the second type of oscillator, based on the exhibition of high lift coefficients. For a wing-type oscillator, an optimum elastic modulus for an air-foil was found. For a self-induced vibration-type mechanism, based on analysis of vorticity and velocity distribution, a square-shaped head exhibited a lift coefficient of more than two times that of a cylindrically shaped head. Analysis of the flow field clearly showed that the discontinuous flow caused by a square-headed oscillator results in higher lift coefficients due to intense vortex shedding, and that stable operation can be achieved by selecting the optimum length to width ratio.
Highlights
We have been faced with issues such as global warming and depletion of fossil fuels
As Japan is surrounded by the sea which provides stable ocean currents throughout the year, we propose an oscillatory-type tidal current-powered generator based on robotic fish technology
(1) An airfoil-shaped oscillator with optimal elasticity effectively increases lift, and we found that the elastic modulus E = 106 Pa is the best for a NACA0015 model foil
Summary
We have been faced with issues such as global warming and depletion of fossil fuels. A water flow-powered generator using generator using pendulum-oscillation has been developed at Okayama University [6,7], which uses pendulum-oscillation has been developed at Okayama University [6,7], which uses the same principle the same principle as the VIVACE system. With regard to determining the optimal elastic modulus reciprocating-type power generating system. The purpose of this study is as the oscillator is the main part of a reciprocating type generator, it’s design is critical. The fundamental equations of the two-way coupled problem are as follows: The unsteady flow field (incompressible) around the oscillator is governed by the following. Hereforce.is the mass of the solid, is the acceleration, is the stress tensor on the solid and equations are (displacement d, fluid subscript f, and solid s): isThe the coupling body force.
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