Effects of aeroelasticity and wind direction on the aerodynamic characteristics and structural responses of blades for horizontal-axis wind turbines under typhoons

Abstract

Flexible blades of horizontal-axis wind turbines (HAWTs) have severe aeroelastic issues under typhoons. Fluid-structure interaction studies which incorporated computational fluid dynamics (CFD) and finite element method (FEM) were conducted to investigate the effects of aeroelasticity and wind direction (θ, relative to the normal of rotor's plane) on the aerodynamics and responses of blades under low-turbulence typhoons. Under the fully considered aeroelasticity, the increase in blade thrust fluctuation at θ = 90° was larger than those at θ = 0° and 180°. The vortex shedding of upstream blade at θ = 90° increased the thrust variation of downstream blade. The flapwise thrust on Blade 3 (azimuth angle of 240°, relative to the vertical direction in rotor's plane) increased by 109.30 % at θ = 90° under the fully considered aeroelasticity and upstream interference. Under the full consideration of aeroelasticity, the significant displacement-induced flow separation at θ = 90° increases the fluctuation in wind load. Large wind load variations increase aerodynamic damping, decreasing the fluctuations in blade-tip displacement (Δ) and blade-root moment (M). The decreases in Δ and M reduce the maximum stress of blade. The vortex shedding of flexible blades at θ = 90° increases the structural safety of HAWTs under typhoons.