scholarly journals Three-Dimensional CFD Simulation and Experimental Assessment of the Performance of a H-Shape Vertical-Axis Wind Turbine at Design and Off-Design Conditions

2019 ◽  
Vol 4 (3) ◽  
pp. 30 ◽  
Author(s):  
Nicoletta Franchina ◽  
Otman Kouaissah ◽  
Giacomo Persico ◽  
Marco Savini
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
Computational Cost ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Numerical Predictions

The paper presents the results of a computational study on the aerodynamics and the performance of a small-scale Vertical-Axis Wind Turbine (VAWT) for distributed micro-generation. The complexity of VAWT aerodynamics, which are inherently unsteady and three-dimensional, makes high-fidelity flow models extremely demanding in terms of computational cost, limiting the analysis to mainly 2D or 2.5D Computational Fluid-Dynamics (CFD) approaches. This paper discusses how a proper setting of the computational model opens the way for carrying out fully 3D unsteady CFD simulations of a VAWT. Key aspects of the flow model and of the numerical solution are discussed, in view of limiting the computational cost while maintaining the reliability of the predictions. A set of operating conditions is considered, in terms of tip-speed-ratio (TSR), covering both peak efficiency condition as well as off-design operation. The fidelity of the numerical predictions is assessed via a systematic comparison with the experimental benchmark data available for this turbine, consisting of both performance and wake measurements carried out in the large-scale wind tunnel of the Politecnico di Milano. The analysis of the flow field on the equatorial plane allows highlighting its time-dependent evolution, with the aim of identifying both the periodic flow structures and the onset of dynamic stall. The full three-dimensional character of the computations allows investigating the aerodynamics of the struts and the evolution of the trailing vorticity at the tip of the blades, eventually resulting in periodic large-scale vortices.

Comparison of Experimental and Numerically Predicted Three-Dimensional Wake Behaviour of a Vertical Axis Wind Turbine

2017 ◽  
Author(s):  
Joseph Saverin ◽  
David Marten ◽  
David Holst ◽  
George Pechlivanoglou ◽  
Christian Oliver Paschereit ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
Computational Cost ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Tip Vortex ◽  
Vertical Axis Wind Turbine ◽  
Design And Optimization ◽  
Aerodynamic Model ◽  
Lift And Drag

The evolution of the wake of a wind turbine contributes significantly to its operation and performance, as well as to those of machines installed in the vicinity. The inherent unsteady and three-dimensional aerodynamics of Vertical Axis Wind Turbines (VAWT) have hitherto limited the research on wake evolution. In this paper the wakes of both a troposkien and a H-type VAWT rotor are investigated by comparing experiments and calculations. Experiments were carried out in the large-scale wind tunnel of the Politecnico di Milano, where unsteady velocity measurements in the wake were performed by means of hot wire anemometry. The geometry of the rotors was reconstructed in the open-source wind-turbine software QBlade, developed at the TU Berlin. The aerodynamic model makes use of a lifting line free-vortex wake (LLFVW) formulation, including an adapted Beddoes-Leishman unsteady aerodynamic model; airfoil polars are introduced to assign sectional lift and drag coefficients. A wake sensitivity analysis was carried out to maximize the reliability of wake predictions. The calculations are shown to reproduce several wake features observed in the experiments, including blade-tip vortex, dominant and submissive vortical structures, and periodic unsteadiness caused by sectional dynamic stall. The experimental assessment of the simulations illustrates that the LLFVW model is capable of predicting the unsteady wake development with very limited computational cost, thus making the model ideal for the design and optimization of VAWTs.

scholarly journals Numerical evaluation of aerodynamic performances of vertical-axis wind turbine rotor with flow concentrator

2020 ◽  
Author(s):  
Jelena Svorcan ◽  
◽  
Ognjen Peković ◽  
Toni Ivanov ◽  
Miloš Vorkapić ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Flow Simulations ◽  
Wind Speeds

With wind energy extraction constantly increasing, the interest in small-scale urban wind turbines is also expanding. Given that these machines often work in adverse operating conditions (Earth’s boundary layer, vortex trails of surrounding objects, small and changeable wind speeds), additional elements that locally augment wind velocity and facilitate turbine start may be installed. This paper investigates possible benefits of adding an optimized flow concentrator to a vertical-axis wind turbine (VAWT) rotor. Three-dimensional, unsteady, turbulent, incompressible flow simulations of both isolated rotor consisting of three straight blades and a rotor with flow concentrator have been performed in ANSYS FLUENT by finite volume method for several different operational regimes. This type of flow simulations is challenging since flow angles are high, numerous flow phenomena and instabilities are present and the interaction between the blades and detached vortices can be significant. The rotational motion of the blades is solved by the unsteady Sliding Mesh (SM) approach. Flow field is modeled by Unsteady Reynolds Averaged Navier-Stokes (URANS) equations with k-ω SST turbulence model used for closure. Both quantitative and qualitative examinations of the obtained numerical results are presented. In particular, the two computed power coefficient curves are compared and the advantages of installing a flow concentrator are accentuated.

Three-dimensional computational fluid dynamic analysis of a large-scale vertical axis wind turbine

2021 ◽  
pp. 0309524X2110379
Author(s):  
Brian Hand
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Vertical Axis Wind Turbine ◽  
Computational Fluid Dynamics Analysis ◽  
Torque Coefficient

The vertical axis wind turbine (VAWT) configuration has many advantages for an offshore wind turbine Installation. In this paper, the three dimensional (3D) computational fluid dynamics analysis of a large-scale 5 MW VAWT is conducted. At the optimum tip-speed ratio (TSR), the VAWT maximum inline force was 75% larger than the maximum lateral force. It was found the dynamic stall effects cause the VAWT flow field to become increasingly asymmetrical at the mid-span plane, when the TSR is reduced. The attachment of end plates to the blade tips, resulted in a performance improvement during the upwind phase with the average blade torque coefficient in this range being increased by 4.71%. Conversely, during the blade downwind phase a reduction in performance was found due to the increase in drag from the end plates and the average blade torque coefficient in this phase was reduced by 23.1%.

scholarly journals Numerical Analysis of Design Parameters With Strong Influence on the Aerodynamic Efficiency of a Small-Scale Self-Pitch VAWT

2015 ◽  
Author(s):  
Carlos Xisto ◽  
José Páscoa ◽  
Michele Trancossi
Keyword(s):  
Wind Turbine ◽  
Strong Influence ◽  
Vertical Axis ◽  
Periodic Variation ◽  
Numerical Approach ◽  
Design Parameters ◽  
Speed Ratio ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Four Bar Linkage

In the paper, four key design parameters with a strong influence on the performance of a small-scale high solidity variable pitch VAWT (Vertical Axis Wind Turbine), operating at low tip-speed-ratio (TSR) are addressed. To this aim a numerical approach, based on a finite-volume discretization of two-dimensional Unsteady RANS equations on a multiple sliding mesh, is proposed and validated against experimental data. The self-pitch VAWT design is based on a straight blade Darrieus wind turbine with blades that are allowed to pitch around a feathering axis, which is also parallel to the axis of rotation. The pitch angle amplitude and periodic variation are dynamically controlled by a four-bar-linkage system. We only consider the efficiency at low and intermediate TSR, therefore the pitch amplitude is chosen to be a sinusoidal function with a considerable amplitude. The results of this parametric analysis will contribute to define the guidelines for building a full size prototype of a small scale turbine of increased efficiency.

Development of a high-efficiency and long-life 500W class H-Darrieus-type vertical axis wind turbine (VAWT) system using skin-spar-foam sandwich composite structure

2013 ◽  
Vol 20 (4) ◽  
pp. 383-394
Author(s):  
Changduk Kong ◽  
Haseung Lee
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
High Efficiency ◽  
Vertical Axis ◽  
Small Scale ◽  
Test Results ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Structural Test ◽  
The City

AbstractSince the focus on the energy crisis and environmental issues due to excessive fossil fuel consumption, wind power has been considered as an important renewable energy source. Recently, several megawatt-class large-scale wind turbine systems have been developed in some countries. Even though the large-scale wind turbine can effectively produce electrical power, the small-scale wind turbine has been continuously developed due to some advantages; for instance, it can be easily built at a low cost without any limitation of location, i.e., even in the city. In case of small-scale wind turbines, the vertical axis wind turbine (VAWT) is used in the city despite having a lower efficiency than the horizontal axis wind turbine. Furthermore, most small-scale wind turbine systems have been designed at the rated wind speed of around 12 m/s. This aim of this work is to design a high-efficiency 500W class composite VAWT blade that is applicable to relatively low-speed regions. With regard to the aerodynamic design of the blade, parametric studies are carried out to decide an optimal aerodynamic configuration. The aerodynamic efficiency and performance of the designed VAWT is confirmed by computational fluid dynamics analysis. The structural design is performed by the load case study, initial sizing using the netting rule and the rule of mixture, structural analysis using finite element method (FEM), fatigue life estimation and structural test. The prototype blade is manufactured by hand lay-up and the matched die molding. The experimental structural test results are compared with the FEM analysis results. Finally, to evaluate the prototype VAWT including designed blades, the performance test is performed using a truck to simulate various ranges of wind speeds and some measuring equipment. According to the performance evaluation result, the estimated performance agrees well with the experimental test results in all operating ranges.

scholarly journals Numerical Analysis of a Small-Size Vertical-Axis Wind Turbine Performance and Averaged Flow Parameters Around the Rotor

2017 ◽  
Vol 64 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Krzysztof Rogowski ◽  
Ryszard Maroński ◽  
Janusz Piechna
Keyword(s):  
Velocity Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Urban Environments ◽  
Speed Ratio ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Static Pressure Distribution ◽  
Rural And Urban

AbstractSmall-scale vertical-axis wind turbines can be used as a source of electricity in rural and urban environments. According to the authors’ knowledge, there are no validated simplified aerodynamic models of these wind turbines, therefore the use of more advanced techniques, such as for example the computational methods for fluid dynamics is justified. The paper contains performance analysis of the small-scale vertical-axis wind turbine with a large solidity. The averaged velocity field and the averaged static pressure distribution around the rotor have been also analyzed. All numerical results presented in this paper are obtained using the SST k-ω turbulence model. Computed power coeffcients are in good agreement with the experimental results. A small change in the tip speed ratio significantly affects the velocity field. Obtained velocity fields can be further used as a base for simplified aerodynamic methods.

Effect of airfoil and solidity on performance of small scale vertical axis wind turbine using three dimensional CFD model

Energy ◽  
2017 ◽  
Vol 133 ◽  
pp. 179-190 ◽  
Author(s):  
Abhishek Subramanian ◽  
S. Arun Yogesh ◽  
Hrishikesh Sivanandan ◽  
Abhijit Giri ◽  
Madhavan Vasudevan ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Small Scale ◽  
Cfd Model ◽  
Vertical Axis Wind Turbine

Development of a High Efficiency and Long Life 500W Class H-Darrieus Type VAWT (Vertical Axis Wind Turbine) System Using Skin-Spar-Foam Sandwich Composite Structure

2012 ◽  
Author(s):  
Changduk Kong ◽  
Haseung Lee
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Performance Test ◽  
High Efficiency ◽  
Vertical Axis ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Structural Test

Since the energy crisis and the environmental issue have been focused due to excessive fossil fuel consumption, the wind power has been considered as an important renewable energy source. Recently, several MW class large scale wind turbine systems have been developed in some countries. Even though the large scale wind turbine can effectively produce the electrical power, the small scale wind turbines have been continuously developed due some advantages, for instance, it can be easily built by low cost without any limitation of location, i.e. even in city. In case of small scale wind turbines, the vertical axis wind turbine (VAWT) is used in city having frequent wind direction change, even though it has a bit lower efficient than the horizontal axis wind turbine. Furthermore, most small scale wind turbine systems have been designed at the rated wind speed of around 12m/s. This work is to design a high efficiency 500W class composite VAWT blade which is applicable to relatively low speed region. In the aerodynamic design of blade, the parametric studies are carried out to decide an optimal aerodynamic configuration. The aerodynamic efficiency and performance of the designed VAWT is confirmed by the CFD analysis. The structural design is performed by the load case study, the initial sizing using the netting rule and the rule of mixture, the structural analysis using FEM, the fatigue life estimation and the structural test. The prototype blade is manufactured by the hand lay-up and the matched die molding. The experimental structural test results are compared with the FEM analysis results. Finally, to evaluate the prototype VAWT including designed blades, the performance test is performed using a truck to simulate the various range wind speeds and some measuring equipments. According to the performance evaluation result, the estimated performance is well agreed with the experimental test result in all operating ranges.

scholarly journals Aerodynamic Analysis of a Two-Bladed Vertical-Axis Wind Turbine Using a Coupled Unsteady RANS and Actuator Line Model

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 776 ◽  
Author(s):  
Ruiwen Zhao ◽  
Angus C. W. Creech ◽  
Alistair G. L. Borthwick ◽  
Vengatesan Venugopal ◽  
Takafumi Nishino
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Vertical Axis Wind Turbine ◽  
Line Model ◽  
Numerical Predictions ◽  
Vertical Axis Turbine ◽  
Actuator Line Model

Close-packed contra-rotating vertical-axis turbines have potential advantages in wind and hydrokinetic power generation. This paper describes the development of a numerical model of a vertical axis turbine with a torque-controlled system using an actuator line model (ALM). The developed model, coupled with the open-source OpenFOAM computational fluid dynamics (CFD) code, is used to examine the characteristics of turbulent flow behind a single two-bladed vertical-axis turbine (VAT). The flow field containing the turbine is simulated by solving the unsteady Reynolds-averaged Navier-Stokes (URANS) equations with a k - ω shear stress transport (SST) turbulence model. The numerical model is validated against experimental measurements from a two-bladed H-type wind turbine. Turbine loading is predicted, and the vorticity distribution is investigated in the vicinity of the turbine. Satisfactory overall agreement is obtained between numerical predictions and measured data on thrust coefficients. The model captures important three-dimensional flow features that contribute to wake recovery behind a vertical-axis turbine, which will be useful for future studies of close-packed rotors with a large number of blades.

scholarly journals Analysis and implementation of a drag-type vertical-axis wind turbine for small distributed wind energy systems

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401982570 ◽  
Author(s):  
Zheng Li ◽  
Ruihua Han ◽  
Peifeng Gao ◽  
Caisheng Wang
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Energy Systems ◽  
Vertical Axis ◽  
Small Scale ◽  
Prototype System ◽  
Vertical Axis Wind Turbine ◽  
Simulation Results ◽  
Wind Energy Systems

This article investigates a drag-type vertical-axis wind turbine that is targeted for small-scale wind energy system applications. Based on aerodynamics models, the three-dimensional simulation studies have been carried out to obtain the force distributions along blades and eventually the torque and power coefficients for different vertical-axis wind turbine configurations. An optimal vertical-axis wind turbine configuration is chosen based on the comparative analysis, and a 2 kW prototype system has been implemented based on the design. The effectiveness of the three-dimensional models and simulation results has been verified by the measured data from the actual vertical-axis wind turbine system. The wake impacts to the vertical-axis wind turbine caused by nearby objects are also analyzed. The simulation results and the actual operation experiences show that the proposed system has the characteristics of low cut-in speed, high power density, and robustness to adjacent objects (such as buildings and other wind turbines), which make it suitable for small-scale wind energy systems in populated areas including urban environment.

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