Solidity effects and azimuth angles on flow field aerodynamics and performance of vertical axis wind turbines at low Reynolds number

Abstract

Solidity is an important parameter in the design, manufacture, and operation concerning energy yield and performance efficiency of VAWTs. This paper examined detailed aerodynamic analysis of solidity effects at constant Re and at low Reynolds numbers, the flow field and forces (lift, drag, and Torque coefficients) aerodynamics at various azimuth positions, and the changes in the performance and the flow field of VAWTs at a wide range of TSR. The simulation of two three-bladed VAWT configurations, σ = 0.26 (C = 0.03 m) and σ = 0.34 C = 0.04 m) over 1.5 ≤ λ ≤ 5.5 tip speed ratios on the CL, CD, CM, and speed were monitored and extracted, and the blades surrounding flow field is plotted from the CFD simulations. Performance (Cp -λ) curves, force hysteresis, and plots of the flow field for the turbines are matched at low λ = 2 5, high λ = 4, and Reynolds number to explain solidity effects on the VAWTs performance and aerodynamics thus providing good insight into the underlying aerodynamics for the differences in power coefficient between the two rotors in detail. This allowed the linking of the performance to the detailed force and flow field aerodynamics at various azimuth angles. It has been shown that the initiation of blade stall and stall vortices shedding started earlier on the σ = 0.26 VAWT than the σ =0.34 VAWT, thus affecting the force attained and ultimately limiting the rotor efficiency of σ = 0.26 compared with the σ =0.34 rotor and provided an improved understanding of solidity phenomenon that will help in the design, production and operation of VAWTs.

Keywords

• Solidity
• Performance aerodynamics
• Flow field
• Azimuth angle
• Computational fluid dynamics