Horizontal Axis Wind Turbine Aerodynamics: Three- Dimensional, Unsteady, and Separated Flow Influences (original) (raw)
FLUID DYNAMICS SIMULATION OF A THREE– BLADED HORIZONTAL AXISWIND TURBINE
IAEME PUBLICATION, 2024
In this study, we present a comprehensive analysis utilizing Computational Fluid Dynamics (CFD) simulation techniques to investigate the aerodynamic performance of a three-bladed Horizontal Axis Wind Turbine (HAWT). The aim of this research is to gain insights into the complex flow phenomena and efficiency characteristics associated with the turbine's operation. With the increasing global demand for renewable energy sources, wind turbines have gained prominence as a sustainable solution for electricity generation. The aerodynamic efficiency of the turbine blades plays a crucial role in maximizing energy extraction from the wind flow. A detailed 3D geometry of the HAWT, including therotor blades, nacelle, and tower, is developed and meshed appropriately for an accurate representation of flow. Through systematic simulations, the velocity field, pressure distribution, and turbulence patterns around the wind turbine blades are visualized and analyzed. This study underscores the significance of employing CFD simulations as a valuable tool for evaluating wind turbine performance, thus paving the way for advancements in renewable energy technology through improved turbine design and enhanced energy output.
2017
Unsteady flow physics of two types of vertical axis wind turbines (VAWTs), namely, a modified Savonius turbine and a hybrid Darrieus-modified-Savonius (HDMS) turbine, are numerically studied using a fluid-structure interaction approach. As a first step, a numerical solver is developed by coupling the wind turbine dynamics with a high-fidelity flow solver, thus, synchronizing the flow-turbine interaction. The solver is then used to study unsteady aerodynamics of wind-driven modified Savonius and HDMS VAWTs under different loading conditions. The relationship between the power efficiency and tip speed ratio (TSR) is invested for both types of wind turbines. It is found that there exists large disparity on energy harvesting performance between the two types of VAWTs under wind-driven flow conditions. The modified Savonius VAWT achieves relatively high power efficiency (~30% or ~51% of the Betz's limit) at small TSRs; the HDMS VAWT achieves high power efficiency (~40% or ~67% of the Betz's limit) at large TSRs. At the same incoming wind speed, the maximum power efficiency of the HDMS VAWT is about 10% higher than that of the Savonius VAWT. It is also observed that the external loading can affect dynamic stall over Darrieus blades of the HDMS VAWT, thus significantly varying the TSR and the corresponding energy harvesting efficiency.
Renewable and Sustainable Energy Reviews, 2016
Horizontal-axis wind turbines (HAWTs) are the primary devices used in the wind energy sector. Systems used to evaluate the design of turbine blades and generators are key to improve the performance of HAWTs. Analysis of aerodynamic performance in turbine blades focuses on wind speed, rotational speed, and tip speed ratios (TSRs). This paper reviews computational as well as experimental methods used to measure the aerodynamic performance of HAWT blades. Among the numerical methods, we examine classical blade element momentum (BEM) theory and the modified BEM as well as computational fluid dynamics (CFD) and the BEM-CFD mixed approach. We also discuss the current computational methods for investigating turbine wake flows. Among the experimental methods, we examine field testing and wind tunnel experiment including aerodynamic torque measurement and blockage effects. A comparison of numerical and experimental approaches can help to improve accuracy in the prediction of wind turbine performance and facilitate the design of HAWT blades.
In this work we find out suitable settings with which 2D analysis of DarrieusVAWT (Vertical Axis Wind Turbine)can be performed in ANSYS Fluent for acceptable results also this work provides optimum Tip-Speed Ratio for performance optimization. Aerofoil shapes like NACA-0021 & S-1046 were selected for this study. Analysis through various CFD softwares is relatively economical and less time consuming, but results of such software's are greatly influenced by the input parameters like Velocity, Viscosity, Turbulence at input, boundary conditions, etc; also the mathematical models incorporated in these study. Due to input conditions the flow comes out to be fairly turbulent encouraging us to consider Turbulence model widely used in such type of studies, they are k-ε, k-ω & SST (Shear Stress Transport). The outcomes of these three models were compared for both aero-foil profiles focusing on areas like near blades, in rotor domains, in fluid domains, etc. SST model comes out as best among them in terms of predicting variations in fluid and near wall domains. This study will help future VAWT researchers to set fluent solver for quick and acceptable result. Analysis on 2D aerofoil was performed with these settings and compared with experimental results from literatures to check the orientation of this study.Parametricoptimizations of VAWT under different TSR ratio are done.
Journal of Wind Engineering and Industrial Aerodynamics, 2014
A fluctuating free-stream in unsteady wind environment presents a more significant challenge in wind turbine performance. In this paper, a numerical method is presented to investigate the influence of operating conditions on Vertical Axis Wind Turbine (VAWT) of NACA00XX symmetric airfoils with 12% and 22% thickness in unsteady wind condition. The Computational Fluid Dynamics (CFD) numerical method was used to analyze the aerodynamic performance and physics of flow of the VAWT. The VAWT dynamic motion of blades was introduced by sinusoidally oscillating both VAWT blades. Using a validated CFD model, steady wind simulations at U mean ¼7.00 m/s and 11.00 m/s were conducted and the results predicted the Power Coefficient (CP) performance for the VAWT scale. The results derived in the numerical analysis show that, within fluctuating free-stream wind conditions, thicker airfoils are desirable. Overall maximum unsteady CP of VAWT with thicker blades reveals positive deviations if the tip speed ratio λ is slightly higher than λ of the steady maximum CP, while thinner blades maximum CP marginally drops from the steady maximum CP for the same λ range. Higher frequencies of fluctuation marginally improve the unsteady wind performance of both VAWT blade profiles. High fluctuation amplitudes reveal overall performance degradation on both VAWT blade profiles more than small fluctuation amplitudes. The findings lend substantially to our understanding of both the kinematic and aerodynamic behavior on VAWT scale blades operating in unsteady wind condition, and the flow physics that causes the behavior.
Energies, 2013
Three different horizontal axis wind turbine (HAWT) blade geometries with the same diameter of 0.72 m using the same NACA4418 airfoil profile have been investigated both experimentally and numerically. The first is an optimum (OPT) blade shape, obtained using improved blade element momentum (BEM) theory. A detailed description of the blade geometry is also given. The second is an untapered and optimum twist (UOT) blade with the same twist distributions as the OPT blade. The third blade is untapered and untwisted (UUT). Wind tunnel experiments were used to measure the power coefficients of these blades, and the results indicate that both the OPT and UOT blades perform with the same maximum power coefficient, C p = 0.428, but it is located at different tip speed ratio, λ = 4.92 for the OPT blade and λ = 4.32 for the UOT blade. The UUT blade has a maximum power coefficient of C p = 0.210 at λ = 3.86. After the tests, numerical simulations were performed using a full three-dimensional computational fluid dynamics (CFD) method using the k-ω SST turbulence model. It has been found that CFD predictions reproduce the most accurate model power coefficients. The good agreement between the measured and computed power coefficients of the three models strongly
3D CFD model for the analysis of the flow field through a horizontal axis wind turbine (HAWT)
Acta Polytechnica
With the world’s growing demand for energy, renewable energy production has become important in providing alternative sources of energy and in reducing the greenhouse effect. This study investigates the aerodynamics and performance of the WG/EV100 micro–Horizontal Axis Wind Turbine (HAWT) using Computational Fluid Dynamics (CFD). The complexity of VAWT aerodynamics, which is inherently unsteady and three-dimensional, makes high-fidelity flow models extremely demanding in terms of computational cost, limiting the analysis to mainly 2D Computational Fluid-Dynamics (CFD) approaches. This article explains how to perform a full 3D unsteady CFD simulation of HAWT. All main parts of the WG/EV100 HAWT were designed in SOLIDWORKS. Only the blade design was reverse engineered due to the unavailability of the CAD model and the complexity of its geometric characteristics. The impeller blade is scanned using a Coordi-nate Measuring Machine (CMM), and the obtained 3D scan data are exported from t...
Journal of Solar Energy Engineering-transactions of The Asme, 2005
The aerodynamic performance of the National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine (HAWT) under yawed flow conditions is studied using a three-dimensional unsteady viscous flow analysis. Simulations have been performed for upwind cases at several wind speeds and yaw angles. Results presented include radial distribution of the normal and tangential forces, shaft torque, root flap moment, and surface pressure distributions at selected radial locations. The results are compared with the experimental data for the NREL Phase VI rotor. At low wind speeds ͑ϳ7 m/s͒ where the flow is fully attached, even an algebraic turbulence model based simulation gives good agreement with measurements. When the flow is massively separated (wind speed of 20 m/s or above), many of the computed quantities become insensitive to turbulence and transition model effects, and the calculations show overall agreement with experiments. When the flow is partially separated at wind speed above 15 m/s, encouraging results were obtained with a combination of the Spalart-Allmaras turbulence model and Eppler's transition model only at high enough wind speeds.
Wind Energy
Growing horizontal axis wind turbines are increasingly exposed to significant sources of unsteadiness, such as tower shadowing, yawed or waked conditions and environmental effects. Due to increased dimensions, the use of steady tabulated airfoil coefficients to determine the airloads along long blades can be questioned in those numerical fluid models that do not have the sufficient resolution to solve explicitly and dynamically the flow close to the blade. Various models exist to describe unsteady aerodynamics (UA). However, they have been mainly implemented in engineering models, which lack the complete capability of describing the unsteady and multiscale nature of wind energy. To improve the description of the blades' aerodynamic response, a 2D unsteady aerodynamics model is used in this work to estimate the airloads of the actuator line model in our fluid-structure interaction (FSI) solver, based on 3D large eddy simulation. At each section along the actuator lines, a semiempirical Beddoes-Leishman model includes the effects of noncirculatory terms, unsteady trailing edge separation, and dynamic stall in the dynamic evaluation of the airfoils' aerodynamic coefficients. The aeroelastic response of a utility-scale wind turbine under uniform, laminar and turbulent, sheared inflows is examined with oneand two-way FSI coupling between the blades' structural dynamics and local airloads, with and without the enhanced aerodynamics' description. The results show that the external half of the blade is dominated by aeroelastic effects, whereas the internal one is dominated by significant UA phenomena, which was possible to represent only thanks to the additional model implemented.