Numerical Analysis of the Dynamic Interaction between Two Closely Spaced Vertical-Axis Wind Turbines

Yutaka Hara,Tomoyuki Okinaga,Yoshifumi Jodai,Masaru Furukawa

doi:10.3390/en14082286

Yutaka Hara, Tomoyuki Okinaga + Show 2 more

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https://doi.org/10.3390/en14082286

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Abstract

To investigate the optimum layouts of small vertical-axis wind turbines, a two-dimensional analysis of dynamic fluid body interaction is performed via computational fluid dynamics for a rotor pair in various configurations. The rotational speed of each turbine rotor (diameter: D = 50 mm) varies based on the equation of motion. First, the dependence of rotor performance on the gap distance (gap) between two rotors is investigated. For parallel layouts, counter-down (CD) layouts with blades moving downwind in the gap region yield a higher mean power than counter-up (CU) layouts with blades moving upwind in the gap region. CD layouts with gap/D = 0.5–1.0 yield a maximum average power that is 23% higher than that of an isolated single rotor. Assuming isotropic bidirectional wind speed, co-rotating (CO) layouts with the same rotational direction are superior to the combination of CD and CU layouts regardless of the gap distance. For tandem layouts, the inverse-rotation (IR) configuration shows an earlier wake recovery than the CO configuration. For 16-wind-direction layouts, both the IR and CO configurations indicate similar power distribution at gap/D = 2.0. For the first time, this study demonstrates the phase synchronization of two rotors via numerical simulation.

Highlights

In a wind farm comprising numerous large-scale horizontal-axis wind turbines (HAWTs), the distance between adjacent turbine rotors must be several times longer than the rotor diameter
Vertical-axis wind turbines (VAWTs) do not prevail currently, as the basis for considering the optimal layout of the vertical-axis wind turbines (VAWTs) wind farm, Rajagopalan et al conducted computational fluid dynamics (CFD) simulations assuming a two-dimensional (2D) laminar flow field [3]. Their results indicated that the rotors on the downwind side, but outside of the wake, produced a higher power output than the first-row rotors that faced the undisturbed flow owing to the interactions between the VAWT rotors
Dabiri et al proposed the possibility of closely spaced counter-rotating VAWT arrays, which can enhance the wind farm power density to a greater degree than existing HAWT wind farms; they conducted a numerical simulation based on a potential flow model incorporating velocity deficit [4] and field experiments using actual small VAWTs (Windspire: 1.2 kW) [5,6]

Summary

Introduction

In a wind farm comprising numerous large-scale horizontal-axis wind turbines (HAWTs), the distance between adjacent turbine rotors must be several times longer than the rotor diameter. Vertical-axis wind turbines (VAWTs) do not prevail currently, as the basis for considering the optimal layout of the VAWT wind farm, Rajagopalan et al conducted computational fluid dynamics (CFD) simulations assuming a two-dimensional (2D) laminar flow field [3]. Their results indicated that the rotors on the downwind side, but outside of the wake, produced a higher power output than the first-row rotors that faced the undisturbed flow owing to the interactions between the VAWT rotors.

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