Aerodynamics of Wind Turbines (original) (raw)
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Energy, 2015
The one-dimensional momentum theory is essential for understating the physical mechanism behind the phenomena of the DAWT (Diffuser-Augmented Wind Turbines). The present work tries to extend the existing GADT (Generalized Actuator Disc Theory) that proposed by Jamieson (2008). Firstly, the GADT is modified to include an effective diffuser efficiency, which is affected by the thrust loading or axial induction. Secondly, Glauert corrections to the DAWT system in the turbulent wake state are proposed, modelled by a linear and a quadratic approximation, respectively. Finally, for prediction of the axial velocity profile at rotor plane bearing various thrust loadings, an empirical model is established, which can be further used to predict the diffuser axial induction. In addition, the 'cut-off point' in Glauert correction and the 'critical thrust loading' in axial velocity profile prediction are newly defined to assist the analysis. All the above formulations have been compared and validated with Jamieson's results and Hansen's CFD data, justifying the effectiveness of the present model.
The Effective Aerodynamic Forces on the Blade and the Rotor of the Wind Turbine
2014
Betz theory presents the output power from the disk of wind turbine but the density of the power on the disk (the density of the forces along the blade) isn't cleared. Designing the profile of a wind turbine blade involves determining the aerodynamics and distribution of the lift forces along the blade. There is new method to calculate the relative velocity depending on knowing values ? Wake rotational speed and ? Blade rotational speed [3], by this method the relative velocity will be known and the lift force will be known theoretically so knowing the efficient lift at particular parts of the blade will help engineers to develop design solutions for improving wind turbine output. This paper studies the distribution of relative velocity and the lift forces along the blade, this values will be calculated depended on several values of the tip speed ratio (TSR) for every situation.
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
Progress in Computational Fluid Dynamics, An International Journal, 2014
Traditional Blade Element Momentum (BEM) methods based on 2-dimensional data are unable to accurately predict blade forces and thus are unreliable when used in actuator discs to predict wind turbine wake profiles. This can be circumvented by extracting relevant force and velocity data from direct modeling simulations or experiments, which are almost certainly used in the design process of a wind turbine.
2020
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...
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/aerodynamic-performance-evaluation-of-a-wind-turbine-blade-by-computational-and-experimental-method https://www.ijert.org/research/aerodynamic-performance-evaluation-of-a-wind-turbine-blade-by-computational-and-experimental-method-IJERTV3IS060103.pdf Lift and Drag forces along with the angle of attack are the important parameters in a wind turbine system. These parameters decide the efficiency of the wind turbine. In this paper an attempt is made to study the Lift and Drag forces in a wind turbine blade at various sections and the effect of angle of attack on these forces. In this paper NACA 4420 airfoil profile is considered for analysis of wind turbine blade. The wind turbine blade is modelled and several sections are created from root to tip. The Lift and Drag forces are calculated at different sections for angle of attack from 0° to 20° for low Reynolds number. The analysis showed that angle of attack of 6° has high Lift/Drag ratio. The CFD analysis is also carried out at various sections of blade at different angle of attack. The pressure and velocity distributions are also plotted. The airfoil NACA 4420 is analyzed based on computational fluid dynamics to identify its suitability for its application on wind turbine blades and good agreement is made between results.
51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2013
The paper presents the implementation of the Actuator Cylinder (AC) flow model in the HAWC2 aeroelastic code originally developed for simulation of Horizontal Axis Wind Turbine (HAWT) aeroelasticity. This is done within the DeepWind project where the main objective is to explore the competitiveness of VAWTs for floating MW concepts. The AC model is a 2D flow model and has thus some advantages compared with the stream tube models often used in VAWT aerodynamic and aeroelastic simulation models. A major finding presented in the present paper is a simple way to correct the results from the linear version of the AC model so that they correlate closely with the results of the full AC model.
Modeling of Aerodynamic Forces on the Wind Turbine Blades
Journal of Clean Energy Technologies, 2015
This research work is aimed to improve the wind turbine modeling for a better representation of aerodynamic forces around the blades. The modeling of forces has been carried out using the actuator surface hybrid model. This model combines the blade element method and Navier-Stokes equation solver. The forces are extracted using real airfoil section of S809 in order to impose on the line which represents the actuator surface. The near wake is calculated and compared with the proposed model and the existing models.
2015
For the last two decades the wind power industry has rapidly increased in Europe becoming one of the most economic renewable energy sources. For a good performance in the capture of the wind energy, one of the most important parts are the blades of the wind turbine. From simple designs for domestic wind turbines to the application of the last technology of aerodynamics for big aero-generators, research in blades (physical design, profile, materials, structure, etc.) is one of the major research fields in electric generation. Blades should be studied primarily from two points of view: the aerodynamic and structural one. Blade element momentum theory is normally used in the optimization process of blade design. In this paper, we present an introduction to the design of blades of a wind turbine for using in a low power and low cost wind generator.
Performance analysis of open and ducted wind turbines
In this paper the analysis of the aerodynamic performance of ducted wind turbines is carried out by means of a nonlinear and semi-analytical actuator disk model. It returns the exact solution in an implicit formulation as superposition of ring vortices properly arranged along the duct surface and the wake region. In comparison with similar and previously developed models, the method can deal with ducts of general shape, wake rotation and rotors characterised by radially varying load distributions. Moreover, the nonlinear mutual interaction between the duct and the turbine, and the divergence of the slipstream, which is particularly relevant for heavily loaded rotors, are naturally accounted for. Present results clearly show that a properly ducted wind turbine can swallow a higher mass flow rate than an open turbine with the same rotor load. Consequently, the ducted turbine achieves a higher value of the extracted power. The paper also presents a detailed comparison between the aforementioned nonlinear and semi-analytical actuator disk method and the widely diffused CFD actuator disk method. The latter is based on the introduction of an actuator disk model in a CFD package describing the effects of the rotor through radial profiles of blade forces distributed over a disk surface. A set of reference numerical data, providing the inviscid axisymmetric velocity and pressure field distributions, are generated with controlled accuracy. Owing to an in-depth analysis of the error generated by the semi-analytical method and to the exactness of the solution in its implicit form, the collected data are well-suited for code-to-code validation of existing or newly developed computational methods.