• Wind and Structures
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• v.35 no.5
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• pp.353-368
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• 2022

Wind turbine blades are adjusted in real-time according to the wind conditions and blade deformations to improve power generation efficiency. It is necessary to predict and reduce the aeroelastic deformations of wind turbine blades. In this paper, the equivalent model of the blade is established by the finite element method (FEM), and the aerodynamic load of the blade is evaluated based on the blade element momentum (BEM) theory. The aeroelastic coupling model is established, in which the bending-torsion coupling effect of the blade is taken into account. The steady and dynamic aeroelastic deformations are calculated. The influences of the blade section's shear centre position and the blade's sweepback design on the deformations are analyzed. The novel approaches of reducing the twist angle of the blade by changing the shear centre position and sweepback of the blade are presented and proven to be feasible.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.125-133
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.677-681
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• 2011

Characteristics of vertical and horizontal axis wind turbines are explained. The speed and direction of wind on the blade of the Darrieus type turbine changes very severely. Therefore dynamic stall happens periodically and the wake from the front blade deteriorates the performance of rear blades. Blade element momentum theory(BEMT) is widely utilized for aerodynamic design and performace prediction of horizontal axis wind turbine(HAWT). Computation analysis and wind tunnel test are also performed for the performance prediction.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.165.1-165.1
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• 2011

In the present study, two numerical methods were developed and compared for the performance prediction of the horizontal axis energy conversion turbine. The Blade Element Momentum Theory was adopted, and the rotating reference frame method for Computational Fluid Dynamics solver was also used. Hybrid meshing was used for the complex geometry of turbines. The analysis results using each method were compared to figure out a better method for the performance prediction.

• The KSFM Journal of Fluid Machinery
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• v.11 no.5
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• pp.15-21
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• 2008

In modem wind power system of large capacity above 1MW, horizontal axis wind turbine(HAWT) is a common type. And, the optimum design of wind turbine to guarantee excellent power performance and its reliability in structure and longevity is a key technology in wind Industry. In this study, mathematical expressions based upon the conventional BEMT(blade element momentum theory) applying to basic 1MW wind turbine blade configuration design. Power coefficient and related flow parameters, such as Prandtl's tip loss coefficient, tangential and axial flow induction factors of the wind turbine analyzed systematically. X-FOIL was used to acquire lift and drag coefficients of the 2-D airfoils and we use Viterna-Corrigan formula to interpolate the aerodynamic characteristics in post-stall region. In order to predict the performance characteristics of the blade, a performance analysis carried out by BEMT method. As a results, axial and tangential flow factors, angle of attack, power coefficient investigated in this study.

• Advances in Energy Research
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• v.6 no.1
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• pp.35-54
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• 2019

A successful blade design must satisfy some criterions which might be in conflict with maximizing annual energy yield for a specified wind speed distribution. These criterions include maximizing power output, more resistance to fatigue loads, reduction of tip deflection, avoid resonance and minimize weight and cost. These criterions can be satisfied by modifying the geometrical parameters of the blade. This study is dedicated to the aerodynamic assessment of a 20 kW horizontal axis wind turbine operating with two possible airfoils; that is $G{\ddot{o}}ttingen$ 413 and NACA 2415 airfoils (the Gottingen airfoil never been used in wind turbines). For this study parameters such as chord (constant, tapered and elliptic), twist angle (constant and linear) are varied and applied to the two airfoils independently in order to determine the most adequate blade configuration that produce the highest annual energy output. A home built numerical code based on the Blade Element Momentum (BEM) method with both Prandtl tip loss correction and Glauert correction, X-Foil and Weibull distribution is developed in Matlab and validated against available numerical and experimental data. The results of the assessment showed that the NACA 2415 airfoil section with elliptic chord and constant twist angle distributions produced the highest annual energy production.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.23 no.4
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• pp.367-380
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• 2019

A 1kW-class horizontal axis wind turbine (HAWT) rotor blade is taken into account to investigate elastic characteristics in 2-D. The elastic blade field is composed of symmetric cross-ply laminated composite material. Blade element momentum theory is applied to obtain the boundary conditions pressuring the blade, and the plane stress elasticity problem is formulated in terms of two displacement parameters with mixed boundary conditions. For the elastic characteristics a fair of differential equations are derived based on the elastic theory. The domain is divided by triangular and rectangular elements due to the complexity of the blade configuration, and a finite element method is developed for the governing equations to search approximate solutions. The results describe that the elastic behavior is deeply influenced by the layered angle of the middle laminate and the stability of the blade can be improved by controlling the layered angle of laminates, which can be evaluated by the mathematical approach.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.1021-1040
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• 2015

An effective method to calculate aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structures in yaw condition is proposed. By a case study on a 5 MW large wind turbine, the finite element model of the wind turbine tower-blade coupled structure is established to obtain the modal information. The harmonic superposition method and modified blade-element momentum theory are used to calculate aerodynamic loads in yaw condition, in which the wind shear, tower shadow, tower-blade modal and aerodynamic interactions, and rotational effects are fully taken into account. The mode superposition method is used to calculate kinetic equation of wind turbine tower-blade coupled structure in time domain. The induced velocity and dynamic loads are updated through iterative loop, and the aeroelastic responses of large wind turbine tower-blade coupled system are then obtained. For completeness, the yaw effect and aeroelastic effect on aerodynamic loads and wind-induced responses are discussed in detail based on the calculating results.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.57.2-57.2
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• 2011

In this study, the effects of shear flows around a 2-dimensional airfoil, S809 on its aerodynamic characteristics were analyzed by CFD simulations. Various parameters including reference inflow velocity, shear rate, angle of attack, and cord length of the airfoil were examined. From the simulation results, several important characteristics were found. Shear rate in a flow makes some changes in the lift coefficient depending on its sign and magnitude but angle of attack does not have a distinguishable influence. Cord length and reference inflow also cause proportional and inversely proportional changes in lift coefficient, respectively. We adopted an analytic expression for the lift coefficient from the thin airfoil theory and proposed a modified form applicable to the traditional load analysis procedure based on the blade element momentum theory. Some preliminary results applied to an well known load simulation software, FAST, are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.2
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• pp.134-143
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• 2014

A significant degradation in the aerodynamic performance of wind turbine system can occur by ice accretion on the surface of blades operated in cold climate. The ice accretion can result in performance loss, overloading due to delayed stall, excessive vibration associated with mass imbalance, ice shedding, instrumental measurement errors, and, in worst case, wind turbine system shutdown. In this study, the effects of ice accretions on the aerodynamic characteristics of wind turbine blade sections are investigated on the basis of modern CFD method. In addition, the computational results are used to predict the performance of three-dimensional wind turbine blade system through the blade element momentum method. It is shown that the thickness of ice accretion increases from the root to the tip and the effects of icing conditions such as relative wind velocity play significant role in the shape of ice accretion.