Implementation of the Actuator Cylinder flow model in the HAWC2 code for aeroelastic simulations on Vertical Axis Wind Turbines (original) (raw)
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Development of existing and innovative aerodynamic models for the Darrieus wind turbine has become very popular in recent years. Since research in the field of aerodynamics of the Darrieus concept is very limited, the development of simplified aerodynamic methods is very difficult. Therefore, the major objective of the present study is to present the concept of a new aerodynamic model for the Darrieus wind turbine – the actuator cell model (ACM). Aerodynamic loads are added to the unsteady incompressible Navier-Stokes equations as momentum source terms. The source terms are computed basing on instantaneous aerodynamic forces taken from the literature. The numerical results of wake structure computed by ACM are compared with the experimental data. Agreement between the numerical results of velocity profiles and the experimental data is reasonably good. 1. Introduction Development of simplified aerodynamic models giving reasonable results of aerodynamic loads and wake structure for the Darrieus wind turbine is a challenge. The most popular aerodynamic model for the Darrieus wind turbine is the double multiple streamtube model (DMS) developed by Paraschivoiu [1]. Computations of aerodynamic blade loads basing on this model are very fast, however, its use is limited [2]. The DMS model fails for a large rotor solidity and for heavily loaded blades because the flow past the rotor is assumed to be quasi steady. Vortex models, based on vorticity equations, are another group of simplified aerodynamic models for the Darrieus concept. These models are computationally expensive and more accurate in comparison with momentum-based methods [3, 4]. Nowadays, Computational Fluid Dynamics (CFD) is becoming an important tool for calculating the complex unsteady flow around the rotor of a vertical axis wind turbine. CFD simulations of VAWTs are, however, very expensive and they are also limited [5-7]. A new trend in modelling of large onshore and offshore wind farms are CFD models that are combined with simplified aerodynamic models. CFD models allow modelling of complex terrain or complex forest environment whereas simplified models, such as, for example, blade element momentum method (BEM), can efficiently calculate aerodynamic blade loads. Such simplified CFD models allow a significant reduction of the computation time. The combination of the BEM code with the incompressible Navier-Stokes equations for aerodynamic analysis of wind turbine with a horizontal axis of rotation was performed by Mikkelsen [8]. The 3D Navier-Stokes equations with the large eddy simulation (LES) model combining with the actuator line technique were applied by Troldborg [9] for the analysis of wake behind horizontal axis wind turbine operating at various flow conditions. Rajagopalan and Fanucci [10] were among the first who performed the computations of a two-dimensional vertical axis wind turbine using a finite difference procedure where turbine blades were replaced by a porous cylindrical shell having a thickness of one volume control. A similar approach for the Darrieus concept was applied by Fortunato et al. [11]. The 2D actuator surface technique for a two-dimensional two-bladed vertical axis wind turbine has been used by Shen et al. [12]. In this approach, the two-dimensional Navier–Stokes equations are used with the k-ω shear stress
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]
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Vertical Axis Wind Turbine- Aerodynamic Modelling and its Testing in Wind Tunnel.pdf
This paper presents aerodynamic modelling, fabrication and the performance evaluation of vertical axis wind turbine (VAWT). Aerodynamic modelling of VAWT is designed using software tools by considering NACA0012 airfoil whose chord length is 0.12 m. Aluminum material based light weight 3 bladed practical prototype model of VAWT having rotor diameter and rotor height as 0.36 m and 0.40 m respectively is fabricated. This practical prototype model is tested in subsonic wind tunnel to analyze the performance parameters like power in the wind, mechanical power at turbine shaft, tip speed ratio (TSR) and power coefficient. The rotor is tested under different wind speeds ranging from 4.38 m/s to 22.38 m/s, test results shows the reliable and efficient performance.
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The advantage of small horizontal axis wind turbines provides a clean and viable option for energy. Although large progress has been achieved in the wind energy sector, there is reduce the cost and improve the performance of small wind turbines. An enhanced understanding of how small wind turbines interact with wind turns out to be essential. Various types of wind turbines are designed to take advantage of wind power based on the principle of aerodynamics. Depending on the wind turbine rotor orientation, there are two types of wind turbine, horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT Currently large no research has concentrated on improving the aerodynamic performance of wind turbine blade through wind tunnel testing and theoretical studies. However wind turbine simulation through computational Fluid Dynamics (CFD) software offers easy solution to aerodynamics blade analysis problem. KEYWORDS: INTRODUCTON Energy is important to human civilisation develop...
Numerical analysis of vertical axis wind turbine
2014 9th International Forum on Strategic Technology (IFOST), 2014
A model for the aerodynamic evaluation of a vertical-axis wind turbine (VAWT) to improve its torque characteristics has been analysed. VAWT is more promising especially in areas with frequent light winds. This paper represent a numerical analysis of the aerodynamics performance on the straight blade fixed pitch VAWT (3 blades) based on the NACA 0018 airfoil. A solid modelling software ANSYS FLUENT which is linked to a finite volume Computational Fluid Dynamics (CFD) is used for the calculation of rotor performance. Gambit software is used to create 2D model of the turbine and the mesh which is generated in Fluent for numerical iterate solution. The Unsteady Reynolds averaged Navier-Stokes equation is used for the investigation of general effects on the performance of several geometry characteristics of two-dimensional airfoils. The RNG k-epsilon model is adopted for the turbulence closure. For proposed rotor analysis, flow field characteristics are investigated at different values of tip speed ratio and also the dynamic quantities such as rotor torque co-efficient and power co-efficient for a constant free stream velocity for 9 m/s which correspond to Reynolds numbers based on chord length of 2.6×10 5 . The VAWT has an inherent unsteady aerodynamic behaviour due to the variation of angle of attack with the angle of rotation, perceived velocity and consequentially Reynolds number. This approach is necessary for having a numerical analysis at low computational cost and time.
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 ...