State of the art in wind turbine aerodynamics and aeroelasticity (original) (raw)

State of the art in the aeroelasticity of wind turbine blades: Aeroelastic modelling

With the continuous increasing size and flexibility of large wind turbine blades, aeroelasticity has been becoming a significant subject for wind turbine blade design. There have been some examples of commercially developed wind turbines experiencing aeroelastic instability problems in the last decade, which spokes for the necessity of aeroelastic modelling of wind turbine blades. This paper presents the state-of-the-art aeroelastic modelling of wind turbine blades, provides a comprehensive review on the available models for aerodynamic, structural and cross-sectional analysis, discusses the advantages and disadvantages of these models, and outlines the current implementations in this field. This paper is written for both researchers new to this research field by summarising underlying theory whilst presenting a comprehensive review on the latest studies, and experts in this research field by providing a comprehensive list of relevant references in which the details of modelling approaches can be obtained.

Unsteady and non-linear aeroelastic analysis of large horizontal-axis wind turbines

International Journal of Hydrogen Energy, 2014

Analysis results, obtained from numerical simulation, for non-linear and unsteady aeroelastic behavior of large horizontal-axis wind turbines are presented in this paper. Simulations are carried out using a partitioned scheme of weak interaction that allows dealing with the fluidestructure interaction problem by using one method to solve the structuraldynamic problem and another method for the aerodynamic problem. The aerodynamic model used is the non-linear, unsteady vortex lattice method (NLUVLM). The structural model used is a system of beam finite elements and rigid bodies with finite rotation. This provides a very general tool with relatively low computational cost. The proposed method allows predicting from the operating conditions (wind speed and direction, pitch angle of blades, etc.) the aeroelastic response of wind turbines, characterized by variables such as rotation speed of the rotor, loads on the structural components and the extracted power, among others.

A Comprehensive Numerical Model for Horizontal Axis Wind Turbines Aeroelasticity

This paper deals with a computational aeroelastic tool aimed at the analysis of performance, response and stability of horizontal axis wind turbines. It couples a nonlinear beam model for blades structural dynamics with an unsteady state-space sectional aerodynamic load model taking into account dynamic stall and inflow effects induced by rotor wake. An extension of 2D static coefficients for high angles of attack is provided to characterize operations in deep stall regime. The Galerkin method is applied to the aeroelastic differential system, with the introduction of a novel approach for the spatial integration of the additional aerodynamic states related to wake vorticity and dynamic stall. Periodic blade responses are determined by a harmonic balance approach and a standard eigenproblem is solved for the stability analysis. Validation of the applied unsteady, sectional aerodynamics model is performed through comparisons with experimental data concerning NACA0012 and S809 airfoil undergoing oscillatory pitch motion. Further, results obtained by the aeroelastic code including dynamic stall modeling applied to the NREL/NASA Ames Phase VI two-bladed rotor in axial flow are presented, with comparisons to available experimental and numerical data. 1 PhD Student, Department of Engineering, angelocalabretta@libero.it 2 Fellow Researcher, PhD, Department of Engineering, marco.molicacolella@uniroma3.it 3 Researcher, CNR-INSEAN Italian Ship Model Basin, luca.greco@cnr.it 4 Researcher, CNR-INSEAN Italian Ship Model Basin, giudubbioso@libero.it 5 Researcher, CNR-INSEAN Italian Ship Model Basin, claudio.testa@cnr.it 6 Professor, Department of Engineering, m.gennaretti@uniroma3.it 2 RUZGEM 2013 t = Time [s] V W = Free stream velocity [m/s] x = Aerodynamic states x' = , aerodynamic states derivatives with respect to non-dimensional time α = Angle of attack [rad] = Angle of attack at ¾ chord point [rad] ω = Motion pulsation [rad/s]

Advanced Aeroservoelastic Modeling for Horizontal axis Wind Turbines

This paper describes the development of a complete methodology for the unsteady aeroelastic and aeroservoelastic modeling of horizontal axis wind turbines at the design stage. The methodology is based on the implementation of unsteady aerodynamic modeling, advanced control strategies and nonlinear finite element calculations in the S4WT wind turbine design package. The aerodynamic modeling is carried out by means of the unsteady Vortex Lattice Method, including a free wake model. The complete model also includes a description of a doubly fed induction generator and its control system for variable speed operation and enhanced power output. The S4WT software features a non-linear finite element solver with multi-body dynamics capability. The complete methodology is used to perform complete aeroservoelastic simulations of a 2MW wind turbine prototype model. The interaction between the three components of the approach is carefully analyzed and presented here.

Aeroservoelastic simulations for horizontal axis wind turbines

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2016

This paper describes the development of a complete methodology for the aeroservoelastic modelling of horizontal axis wind turbines at the conceptual design stage. The methodology is based on the implementation of unsteady aerodynamic modelling, advanced description of the control system and nonlinear finite element calculations in the Samcef Wind Turbines design package. The aerodynamic modelling is carried out by means of fast techniques, such as the blade element method and the unsteady vortex lattice method, including a free wake model. The complete model also includes a description of a doubly fed induction generator and its control system for variable speed operation. The Samcef Wind Turbines software features a nonlinear finite element solver with multi-body dynamics capability. The full methodology is used to perform complete aeroservoelastic simulations of a realistic 2 MW wind turbine model. The interaction between the three components of the approach is carefully analysed ...

Aeroelastic stability of wind turbines: the problem, the methods and the issues

Wind Energy, 2004

Aeroelastic stability is a key issue in the design process of wind turbines towards both enchanced stability and increased fatigue life. The theory and models behind the state-ofthe-art aeroelastic stability tools developed for the analysis of the complete wind turbine at the Centre for Renewable Energy Sources and the National Technical University of Athens are presented in this article. Application examples of stability calculations for a pitch, variable speed and a stall-regulated wind turbine are also presented.

A Framework for Dynamic and Aeroelastic Analysis of Horizontal Axis Wind Turbines

ASME 2002 Wind Energy Symposium, 2002

This paper presents a framework for the dynamic and aeroelastic analysis of a horizontal axis wind turbine modeled as a multi-flexible-body system. The multi-rigid-body portions of the system, composed of the nacelle and hub, are modeled as a system of interconnected rigid bodies using Kane's equations. The flexible portions, composed of the the blades and tower, are represented using nonlinear beam finite elements, taken from a mixed formulation for the dynamics of moving beams. Each analysis leads to a set of symbolic equations that can be coupled symbolically to represent the dynamic behavior of the wind turbine. A solution procedure is implemented to assess the dynamic stability of the system. Here the solution is divided into two parts: a set of nonlinear ordinary differential equations governing the periodic steady-state operating condition, and a set of equations that are linearized about the steady-state operating condition governing the transient dynamics. The harmonic balance method is used for the nonlinear periodic steady-state solution, and the finite element in time method is proposed as an alternative method. Linearization of the equations about the steady-state operating condition yields system equations with periodic coefficients which are solved by Floquet approach to extract the modal parameters. For the aeroelastic analysis, aerodynamic loads from an aerodynamic model to be selected in the future will be inserted into the present framework. Then, the framework can produce a symbolic system matrix, potentially useful for control design. Numerical results are presented for the dynamic characteristic of HAWT's with flexible tower and blades.

MODELING THE STRUCTURAL DYNAMICS OF CHOSEN COMPONENTS OF THE HORIZONTAL AXIS WIND TURBINE

As the horizontal axis wind turbines are getting larger, their dynamic behaviour is becoming more important. Dynamic analysis gives knowledge how to improve efficiency and safety also in small wind turbines. This article describes numerical models of chosen components of upwind, three-bladed wind turbine. Geometry of each component is generated separately and then assembled together by transformation matrices. Material of the blades is composite, the hub is assumed to be made of steel and material of the planet carrier is casted iron. These mentioned components are modelled by shell elements. The numerical model of the hub takes into account aerodynamic and gravity loads of blades, inertia forces due to rotation of the rotor and aerodynamic damping. The aerodynamic loads, calculated according to the modified Blade Element Momentum theory, are attached to aerodynamic centres. Wind conditions were assumed for I-class wind turbine according to Germanischer Lloyd. Stress Reserve Factors were calculated for DLC 6.1 load case according to Germanischer Lloyd, too. As a first step, numerical strength analysis with using AnSYS software was performed with maximum values of principal stresses as an output. Then, based on FEM analysis results, Stress Reserve Factors were calculated. SRF values show that analyzed hub and planet carrier have sufficient strength for extreme loads. Methodology of safety margin evaluation presented in this paper allows assessing if the object fulfils relevant standards demanding.

Modelling the structural dynamics of chosen components of the horizontal axis wind turbine

Journal of KONES, 2011

State of the art in wind turbine aerodynamics and aeroelasticity (original) (raw)

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