scholarly journals Enhancement of Free Vortex Filament Method for Aerodynamic Loads on Rotor Blades

2014 ◽  
Author(s):  
Hamidreza Abedi ◽  
Lars Davidson ◽  
Spyros Voutsinas
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Boundary Layer Separation ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Free Vortex ◽  
Irrotational Flow ◽  
Aerodynamic Loads ◽  
Operational Conditions ◽  
Turbine Rotor Blade

The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is one of the most important challenges in wind turbine rotor blade design. Because of the unsteady flow field around wind turbine blades, prediction of aerodynamic loads with high level of accuracy is difficult and increases the uncertainty of load calculations. A free vortex wake method, based on the potential, inviscid and irrotational flow, is developed to study the aerodynamic loads. Since it is based on the potential, inviscid and irrotational flow, it cannot be used to predict viscous phenomena such as drag and boundary layer separation. Therefore it must be coupled to the tabulated airfoil data to take the viscosity effects into account. The results are compared with the Blade Element Momentum (BEM) [1] method and the GENUVP code [2] (see also the acknowledgments).

scholarly journals Enhancement of Free Vortex Filament Method for Aerodynamic Loads on Rotor Blades

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Hamidreza Abedi ◽  
Lars Davidson ◽  
Spyros Voutsinas
Keyword(s):  
Wind Turbine ◽  
Potential Flow ◽  
Turbine Blades ◽  
Boundary Layer Separation ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Dynamic Stall ◽  
Aerodynamic Loads ◽  
Operational Conditions ◽  
Blade Element

The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is one of the most important challenges in wind turbine rotor blade design. Because of the unsteady flow field around wind turbine blades, prediction of aerodynamic loads with high level of accuracy is difficult and increases the uncertainty of load calculations. An in-house vortex lattice free wake (VLFW) code, based on the inviscid, incompressible, and irrotational flow (potential flow), was developed to study the aerodynamic loads. Since it is based on the potential flow, it cannot be used to predict viscous phenomena such as drag and boundary layer separation. Therefore, it must be coupled to tabulated airfoil data to take the viscosity effects into account. Additionally, a dynamic approach must be introduced to modify the aerodynamic coefficients for unsteady operating conditions. This approach, which is called dynamic stall, adjusts the lift, the drag, and the moment coefficients for each blade element on the basis of the two-dimensional (2D) static airfoil data together with the correction for separated flow. Two different turbines, NREL and MEXICO, are used in the simulations. Predicted normal and tangential forces using the VLFW method are compared with the blade element momentum (BEM) method, the GENUVP code, and the MEXICO wind tunnel measurements. The results show that coupling to the 2D static airfoil data improves the load and power predictions while employing the dynamic stall model to take the time-varying operating conditions into consideration is crucial.

scholarly journals Damage tolerance and structural monitoring for wind turbine blades

2015 ◽  
Vol 373 (2035) ◽  
pp. 20140077 ◽  
Author(s):  
M. McGugan ◽  
G. Pereira ◽  
B. F. Sørensen ◽  
H. Toftegaard ◽  
K. Branner
Keyword(s):  
Wind Turbine ◽  
Damage Tolerance ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Offshore Wind ◽  
Tolerance Index ◽  
Wind Turbine Blades ◽  
Efficient Operation ◽  
Reliable Design

The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind.

scholarly journals Flutter Behavior of Highly Flexible Two- and Three-bladed Wind Turbine Rotors

2021 ◽  
Author(s):  
Mayank Chetan ◽  
Shulong Yao ◽  
D. Todd Griffith
Keyword(s):  
Wind Turbine ◽  
Structural Design ◽  
Comprehensive Evaluation ◽  
Turbine Blades ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flutter Speed ◽  
Cost Of Energy ◽  
Manufacturing Technologies

Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the Levelized Cost of Energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aero-elastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, new rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.

scholarly journals Experimental Investigation of Finite Aspect Ratio Cylindrical Bodies for Accelerated Wind Applications

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 25 ◽  
Author(s):  
Michael Parker ◽  
Douglas Bohl
Keyword(s):  
Aspect Ratio ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Cylindrical Body ◽  
Turbine Rotor ◽  
Flow Speed ◽  
The Body ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Smooth Cylinder

The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area of increased wind speed to enhance energy harvesting. In this work the aerodynamic performance of two short aspect ratio (AR = 0.93) cylindrical bodies was evaluated for potential use in “accelerated wind” applications. The first cylinder was smooth with a constant diameter. The diameter of the second cylinder varied periodically along the span forming channels, or corrugations, where wind turbine blades could be placed. Experiments were performed for Reynolds numbers ranging from 1 × 105 to 9 × 105. Pressure distributions showed that the smooth cylinder had lower minimum pressure coefficients and delayed separation compared to the corrugated cylinder. Velocity profiles showed that the corrugated cylinder had lower peak speeds, a less uniform profile, and lower kinetic energy flux when compared to the smooth cylinder. It was concluded that the smooth cylinder had significantly better potential performance in accelerated wind applications than the corrugated cylinder.

Impact of Blade Flexibility on Wind Turbine Loads and Pitch Settings

2018 ◽  
Author(s):  
Jinge Chen ◽  
Xin Shen ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Wind Turbine ◽  
Aerodynamic Force ◽  
Turbine Blades ◽  
Beam Theory ◽  
Power Production ◽  
Aerodynamic Loads ◽  
Operational Conditions ◽  
Wind Speeds ◽  
Geometrically Exact Beam ◽  
The Impact

Along with the upscaling tendency, lighter and so more flexible wind turbine blades are introduced for reducing cost of manufacture and materials. The flexible blade deforms under aerodynamic loads and in turn affects the flow field, arising the aero-elastic problems. In this paper, the impact of blade flexibility on the wind turbine loads, power production, and pitch actions is discussed. An aeroelastic model is developed for the study. A free wake vortex lattice model is used to calculate the aerodynamic loads, and a geometrically exact beam theory is adopted to compute the structural dynamics of the blade. The flap, lead-lag bending and torsion DOFs are all included and nonlinear effects due to large deflections are considered. The NREL 5MW reference wind turbine is analyzed. Influences of pure-bending and bending-torsion deformations of the blade on aerodynamic loads are compared. The aerodynamic force distributions under various wind speeds for rigid and flexible blades are also compared. The steady state deformations across the operational conditions are calculated, along with the rotor power production. Significant reduction of power is seen especially under large wind speeds, due to the blade twist deformations under torsion moments. Lower pitch angle settings should be applied to maintain the constant power.

scholarly journals Design Studies for Twist-Coupled Wind Turbine Blades

2003 ◽  
Author(s):  
James Locke ◽  
Ulyses Valencia ◽  
Kosuke Ishikawa
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Turbine Blades ◽  
Load Condition ◽  
Turbine Rotor ◽  
Unit Load ◽  
Baseline Design ◽  
Turbine Rotor Blade ◽  
Extreme Wind ◽  
Wind Turbine Rotor

This study presents results obtained for three designs of the Northern Power Systems (NPS) 9.2-meter version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with ±45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Buckling eigenvalues were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads.

scholarly journals Forgószárnyas repülőgép rotorok aeroelasztikus viselkedésének vizsgálata szélturbina lapátok számára kifejelsztett eszközökkel

2019 ◽  
Vol 31 (2) ◽  
pp. 115-126
Author(s):  
Balázs Gáti ◽  
Tamás Gausz
Keyword(s):  
Wind Turbine ◽  
Software Package ◽  
Rotor Blade ◽  
Numerical Solutions ◽  
Turbine Blades ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Operational Conditions ◽  
Rotary Wing ◽  
Multiple Analysis

Rotor blades of an autorotating helicopter or a gyrocopter work very similar to the rotor blades of a wind turbine in skew wind. In this publication we present the result of multiple analysis of a rotor blade of a rotary-wing airplane, but the analyses were performed with a software package developed for investigation of wind turbine blades. The results of several analyses seem to be valid for rotary-wing airplanes in some special, but very important cases, and can be useful for more detailed investigation. It was stated, that the fact leads to uninterpretable numerical solutions, that the angle between the undisturbed airflow and the Tip Path Plane is much lower in case of helicopters and gyrocopters than by wind turbines in most operational conditions .

Basalt Carbon Hybrid Composite for Wind Turbine Rotor Blades: A Short Review

2014 ◽  
Vol 970 ◽  
pp. 67-73 ◽  
Author(s):  
Ali Nawaz Mengal ◽  
Saravanan Karuppanan ◽  
Azmi Abdul Wahab
Keyword(s):  
Composite Material ◽  
Carbon Fiber ◽  
Wind Turbine ◽  
Hybrid Composite ◽  
Turbine Blades ◽  
Basalt Fiber ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Wind Turbine Rotor

Wind turbine blades are the major structural element and highest cost component in the wind power system. Modern wind turbine blade sizes are increasing, and the driving motivation behind this is to increase the efficiency and energy output per unit rotor area, and to reduce the cost per kilowatt hour. However due to the increase in size the material selection for wind turbine has become critical and complex. To achieve the desired materials to improve the design of wind turbine blades several factors such as high fatigue strength, less weight, less cost and potential of recycling must be focused. Basalt fiber is a relative newcomer to fiber reinforced polymers and structural composites. Basalt fiber with their excellent mechanical properties represents an interesting alternative composite material for modern wind turbine blades. Some manufacturers claim that basalt fiber has similar or better properties than S-2 glass fiber and its cheaper than carbon fiber. Basalt fiber together with carbon fiber are the most advanced and interesting area of hybrid technologies. This paper reviews extra ordinary properties of basalt fiber over other fiber reinforced composites and highlight how the basalt special properties together with carbon fiber will reduce the weight and cost of wind turbine blades while improving their performance. This paper also demonstrates why the basalt carbon hybrid composite material will be an ideal alternative for the wind turbine rotor blades.

scholarly journals Effect of Platform Motion on Aerodynamic Performance and Aeroelastic Behavior of Floating Offshore Wind Turbine Blades

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2519 ◽  
Author(s):  
Kim ◽  
Kwon
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Turbine Rotor ◽  
Aerodynamic Performance ◽  
Rotor Blades ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Platform Motion ◽  
Aerodynamic Loads

In the present study, a numerical framework for predicting the aerodynamic performance and the aeroelastic behavior of floating offshore wind turbine rotor blades involving platform motion was developed. For this purpose, the aerodynamic and structural analyses were conducted simultaneously in a tightly coupled manner by exchanging the information about the aerodynamic loads and the elastic blade deformations at every time step. The elastic behavior of the turbine rotor blades was described by adopting a structural model based on the Euler-Bernoulli beam. The aerodynamic loads by the rotor blades were evaluated by adopting a blade element momentum theory. The numerical simulations were conducted when the platform of the wind turbine independently moves in each of the six degrees-of-freedom directions consisting of heave, sway, surge, roll, pitch, and yaw. It was observed that flexible blades exhibit complicated vibratory behaviors when they are excited by the aerodynamic, inertia, and gravitational forces simultaneously. It was found that the load variation caused by the platform surge or pitch motion has a significant influence on the flapwise and torsional deformations of the rotor blades. The torsional deformation mainly occurs in the nose-down direction, and results in a reduction of the aerodynamic loads. It was also found that the flapwise root bending moment is mainly influenced by the platform surge and pitch motions. On the other hand, the edgewise bending moment is mostly dictated by the gravitational force, but is not affected much by the platform motion.

3D Woven Carbon/Glass Hybrid Spar Cap for Wind Turbine Rotor Blade

2006 ◽  
Vol 128 (4) ◽  
pp. 562-573 ◽  
Author(s):  
Mansour H. Mohamed ◽  
Kyle K. Wetzel
Keyword(s):  
Wind Turbine ◽  
Carbon Fibers ◽  
Rotor Blade ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Constant Thickness ◽  
Turbine Rotor Blade ◽  
Parametric Studies ◽  
The Impact ◽  
Wind Turbine Rotor

This paper presents the design and analysis for a spar cap for a wind turbine rotor blade. The cap is formed of an integral, unitary 3D woven material (3WEAVE®) having constant thickness; spar cap weight is varied and controlled by appropriately tapering the cap width from the blade root to tip. This analysis is employed for 24-m and 37-m rotor blades. These studies are conducted parametrically, examining a range of 3WEAVE® materials incorporating varying fractions of glass and carbon fibers, and hence exhibiting a range of structural properties and material costs. These parametric studies are used to determine the impact on blade weight and cost resulting from the various materials studied. Detailed results are presented in the form of tables to enable candidate materials to be evaluated as they are developed.

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