Flutter study of flapwise bend-twist coupled composite wind turbine blades

Farsadi, Touraj
Kayran, Altan
Bending-twisting coupling induced in big composite wind turbine blades is one of the passive control mechanisms which is exploited to mitigate loads incurred due to deformation of the blades. In the present study, flutter characteristics of bend-twist coupled blades, designed for load alleviation in wind turbine systems, are investigated by time-domain analysis. For this purpose, a baseline full GFRP blade, a bend-twist coupled full GFRP blade, and a hybrid GFRP and CFRP bend-twist coupled blade is designed for load reduction purpose for a 5 MW wind turbine model that is set up in the wind turbine multi -body dynamic code PHATAS. For the study of flutter characteristics of the blades, an over-speed analysis of the wind turbine system is performed without using any blade control and applying slowly increasing wind velocity. A detailed procedure of obtaining the flutter wind and rotational speeds from the time responses of the rotational speed of the rotor, flapwise and torsional deformation of the blade tip, and angle of attack and lift coefficient of the tip section of the blade is explained. Results show that flutter wind and rotational speeds of bend-twist coupled blades are lower than the flutter wind and rotational speeds of the baseline blade mainly due to the kinematic coupling between the bending and torsional deformation in bend-twist coupled blades.


Load Reduction in Wind Turbines with Bend-Twist CoupledBlades without Power Loss at Underrated Wind Speeds
Atalay, Oğuz; Kayran, Altan (null; 2018-01-01)
Usage of composite materials in wind turbine blades is a passive mechanism to alleviate fatigue loads besides the reduction in the mass of the wind turbine system. Off-axis plies in bend-twist coupled (BTC) blades account for the passive fatigue load reduction by reducing the effective angle of attack of blade sections. Reduction in fatigue loads is generally represented by damage equivalent load ratios. In the present study, multibody aeroelastic analyses are performed for wind turbine systems for the unde...
Aerodynamic validation studies on the performance analysis of iced wind turbine blades
YIRTICI, ÖZCAN; Cengiz, Kenan; Özgen, Serkan; Tuncer, İsmail Hakkı (Elsevier BV, 2019-10-15)
Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerodynamic characteristic of the blades. In this study ice accretion on turbine blades are simulated under various icing conditions, and the resulting power losses are estimated. The Blade Element Momentum method is employed together with an ice accretion prediction methodology based on the Extended Messinger model in a parallel computing environment. The predicted iced profiles are first validated with the experimen...
Farsadi, Touraj; Şener, Özgün; Kayran, Altan (2017-11-09)
Composite pretwisted rotating thin walled beams (TWB) can be used as the structural model for composite helicopter and wind turbine blades for the study of aeroelastic response of the blades. In the present study, semi-analytical solution is performed for the free vibration analysis of uniform and asymmetric composite pretwisted rotating TWB. The approximation of the Green-Lagrange strain tensor is adopted to derive the strain field of the system. The Euler Lagrange governing equations of the dynamic system...
Assessment of the Effect of Hybrid GFRP CFRP Usage in Wind Turbine Blades on the Reduction of Fatigue Damage Equivalent Loads in the Wind Turbine System
Gözcü, Ozan; Farsadi, Touraj; Şener, Özgün; Kayran, Altan (null; 2015-01-05)
The use of hybrid GFRP-CFRP material in wind turbine blades is investigated for its effectiveness in reducing fatigue damage equivalent loads in the whole wind turbine system, and comparisons are made against the baseline full GFRP blade in terms of strength, deformation, dynamic characteristics, weight and cost of the blade. To achieve load alleviation in the whole wind turbine system, bending-twisting coupling in composite blades is exploited through the use of off-axis plies in the spar caps of the blade...
Performance Study of Wind Turbines with Bend-Twist Coupled Blades at Underrated Wind Speeds
Atalay, Oğuz; Farsadi, Touraj; Kayran, Altan (2017-09-22)
Use of bend-twist coupled blades is one of the ways to alleviate fatigue loads in wind turbine systems. Load reduction is achieved by placing off-axis layers in the spar caps of composite wind turbine blades. Off-axis layers provide twisting of the blade in the feathering direction thereby decreasing the aerodynamic loads due to the reduced effective angle of attack. Reduction of fatigue loads in the wind turbine system is generally measured by the damage equivalent load. In the present study, performance o...
Citation Formats
T. Farsadi and A. Kayran, “Flutter study of flapwise bend-twist coupled composite wind turbine blades,” WIND AND STRUCTURES, pp. 267–281, 2021, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/90153.