Abstract
The effect of non-sinusoidal motion which influences the energy extraction performance of foil is considered in this paper. Two oscillation motions, the combined non-sinusoidal plunging and sinusoidal pitching motion, as well as the combined non-sinusoidal pitching and sinusoidal plunging motion, are selected to investigate the oscillation process of two-dimensional parallel foils numerically. The optimal oscillation motion and average power coefficient at different combined motions are gained. The effects of the plunging motion and pitching motion at different oscillation motions are analyzed, and the evolution law of the foil lift force and vortex field are obtained. It is indicated that the non-sinusoidal motion has a significant influence on energy extraction. When the motion is combined (non-sinusoidal plunging and sinusoidal pitching motion), the best extraction performance is gained at Kh = −0.5. The maximal CPm is 0.375 and the maximal η is 0.188. When the motion is combined (non-sinusoidal pitching and sinusoidal plunging motion), the maximal CPm is 0.623 and the maximal η is 0.312 which appear at Kθ = 2. For the same frequency, the more the plunging motion is similar to the sinusoidal motion, the more energy is extracted by foils. While the more the pitching motion approximates to the square wave, the worse the achieved extraction performance is.
Highlights
As a new energy extraction device using clean energy, foil is thought to have a bright prospect, especially in the current situation of energy shortages and environmental pollution
We considered the effect of non-sinusoidal motion on the energy extraction performance of parallel foils
The results show that both the non-sinusoidal plunging motion and the non-sinusoidal pitching motion have an obvious effect on the energy extraction characteristics of foil
Summary
As a new energy extraction device using clean energy, foil is thought to have a bright prospect, especially in the current situation of energy shortages and environmental pollution. According to the laminar computation model, Campobasso et al [2] simulated the energy extraction performance of foil at a low-velocity flow field with Re = 1100. It was found that the energy extraction efficiency can achieve 35% and the deep stall of airfoil has a positive effect on efficiency. Abiru [3] discussed the energy extraction performance and the effect factors (such as the plunging and pitching amplitude, frequency and the free stream velocity) by experiments. A wind energy extraction device was designed by Shimizu et al [4], which is based on the flutter mechanism of foil. The device worked under a low frequency and gained a high extraction performance and efficiency. Bryant et al [5] established a quasi-stable state model and a semi-empirical model of dynamic stall, optimizing the aerodynamic
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