Numerical Analysis of the Overlap Effect Between Blades at Four-Bladed Rooftop VAWT

2012 ◽  
Author(s):  
H. Flores-Saldaña ◽  
A. Gallegos-Muñoz ◽  
N. C. Uzarraga-Rodriguez ◽  
V. H. Rangel-Hernandez
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Moment Coefficient ◽  
Mesh Model ◽  
The Moment

This work presents a numerical analysis of a four-bladed Rooftop vertical axis wind turbine (VAWT). The effects generated on the performance of turbine by the overlap variation between blades of wind rotor were analyzed. The numerical simulations were developed using commercial software based on Computational Fluid Dynamic (CFD). Each one of the models generated was built in a 3D computational model. A sliding mesh model (SMM) capability was used to present in dimensionless form the moment coefficient and power coefficient of the wind turbine based on the relationship between wind speed and rotor rotational speed. The results show that the aerodynamic performance is better with overlap between rotor blades, resulting in a significant increase in the moment coefficient and power coefficient. Having that in the cases of four-bladed Rooftop rotor with overlap both coefficients increase about 29% comparing with four-bladed Rooftop rotor without overlap between blades.

Numerical Analysis of a Rooftop Vertical Axis Wind Turbine

2011 ◽  
Author(s):  
N. Cristobal Uzarraga-Rodriguez ◽  
A. Gallegos-Mun˜oz ◽  
J. Manuel Riesco A´vila
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Numerical Study ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh ◽  
Mesh Model

A numerical analysis of a rooftop vertical axis wind turbine (VAWT) for applications in urban area is presented. The numerical simulations were developed to study the flow field through the turbine rotor to analyze the aerodynamic performance characteristics of the device. Three different blade numbers of wind turbine are studied, 2, 3 and 4, respectively. Each one of the models was built in a 3D computational model. The effects generated in the performance of turbines by the numbers of blades are considered. A Sliding Mesh Model (SMM) capability was used to present the dimensionless form of coefficient power and coefficient moment of the wind turbine as a function of the wind velocity and the rotor rotational speed. The numerical study was developed in CFD using FLUENT®. The results show the aerodynamic performance for each configuration of wind turbine rotor. In the cases of Rooftop rotor the power coefficient increases as the blade number increases, while in the case of Savonius rotor the power coefficient decrease as the blades number increases.

Computational fluid dynamic analysis of roof-mounted vertical-axis wind turbine with diffuser shroud, flange, and vanes

2018 ◽  
Vol 42 (4) ◽  
pp. 404-415
Author(s):  
H. Abu-Thuraia ◽  
C. Aygun ◽  
M. Paraschivoiu ◽  
M.A. Allard
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes ◽  
Turbine Design

Advances in wind power and tidal power have matured considerably to offer clean and sustainable energy alternatives. Nevertheless, distributed small-scale energy production from wind in urban areas has been disappointing because of very low efficiencies of the turbines. A novel wind turbine design — a seven-bladed Savonius vertical-axis wind turbine (VAWT) that is horizontally oriented inside a diffuser shroud and mounted on top of a building — has been shown to overcome the drawback of low efficiency. The objective this study was to analyze the performance of this novel wind turbine design for different wind directions and for different guide vanes placed at the entrance of the diffuser shroud. The flow field over the turbine and guide vanes was analyzed using computational fluid dynamics (CFD) on a 3D grid for multiple tip-speed ratios (TSRs). Four wind directions and three guide-vane angles were analyzed. The wind-direction analysis indicates that the power coefficient decreases to about half when the wind is oriented at 45° to the main axis of the turbine. The analysis of the guide vanes indicates a maximum power coefficient of 0.33 at a vane angle of 55°.

Simulation on Performances of Vertical Axis Wind Turbine

2010 ◽  
Author(s):  
Chien-Chang Chen ◽  
Cheng-Hsiung Kuo
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Vertical Axis ◽  
Flow Structures ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Moment Coefficient ◽  
Pressure Distributions ◽  
The Moment ◽  
Starting Torque

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.

A Straight-Bladed Vertical Axis Wind Turbine With a Directed Guide Vane: Mechanism of Performance Improvement

2008 ◽  
Author(s):  
Hideki Kuma ◽  
Manabu Takao ◽  
Toshiyuki Beppu ◽  
Takao Maeda ◽  
Yasunari Kamada ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Performance Improvement ◽  
Aerodynamic Force ◽  
Guide Vane ◽  
Vortex Method ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Lagrangian Simulation

A straight-bladed vertical axis wind turbine with a directed guide vane has been proposed in order to enhance its torque. The experimental study of the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has 3 straight rotor blades with a profile of NACA0018, a radius of 0.35 m and a height of 0.7 m. The guide vane which consists of an arc plate rotates around the rotor and is directed to the wind by aerodynamic force generated by tail vanes, so as to put the guide vane in upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed guide vane and the power coefficient of the proposed wind turbine was approximately 1.2 times higher than that of the original wind turbine which has no guide vane. Further, flows around the proposed wind turbine have been investigated by use of the vortex method which provides a Lagrangian simulation of unsteady and vortical flows.

A Straight-Bladed Vertical Axis Wind Turbine With a Directed Guide Vane Row

2007 ◽  
Author(s):  
Manabu Takao ◽  
Takao Maeda ◽  
Yasunari Kamada ◽  
Michiaki Oki ◽  
Hideki Kuma
Keyword(s):  
Experimental Study ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Aerodynamic Force ◽  
Guide Vane ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Vertical Axis Turbine

A straight-bladed vertical axis wind turbine with a directed guide vane row has been proposed in order to enhance its torque. The experimental study of the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has some straight rotor blades with a profile of NACA0015, a radius diameter of 0.3 m and a height of 0.7 m. The guide vane row having 3 arc plates rotates around the rotor and is directed to the wind by aerodynamic force generated by tail vanes, so as to put the guide vane row in upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed guide vane row. Further, by the use of the guide vane row adopted in the study, the power coefficient of the proposed wind turbine was approximately 1.5 times higher than that of the original wind turbine which has no guide vane.

Numerical Analysis of Airfoils Used for Vertical Axis Wind Turbine

2012 ◽  
Author(s):  
N. C. Uzarraga-Rodriguez ◽  
A. Gallegos-Muñoz ◽  
Maria T. Parra-Santos ◽  
Juan M. Belman-Flores
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Stokes Equations ◽  
Numerical Study ◽  
Twist Angle ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Angle Variation ◽  
Straight Blade

A numerical analysis of a three-bladed straight vertical axis wind turbine with NACA0015 airfoils-shaped is presented. The effect generated on the moment coefficient and power coefficient of the wind turbine rotor by the twist angle variation at the chord ends was analyzed. The configurations included the variation of blade twist angle of 15° and 30° located at 70%, 80% and 90% of chord length from leading end of the straight blade. The numerical study was developed in a commercial Computational Fluid Dynamics (CFD) using FLUENT®. This code allows to solve the Reynolds averaged Navier-Stokes equations and the transport equations of the turbulence quantities. The results show the aerodynamic performance for each configuration of the blade twist angle in the wind turbine, and are compared with data obtained from straight blade without twist angle. The wind turbine performance decrease about 67% as the blade twist angle increases, due to an increment in the drag force causing a negative moment against the rotation of vertical axis wind turbine. Also, the surface pressure distribution in a VAWT’s is presented.

scholarly journals Aerodynamic Characteristics of Asymmetric Airfoils Blade Small Vertical Axis Wind Turbines

2014 ◽  
Vol 8 (1) ◽  
pp. 750-753
Author(s):  
Li-Hua Zhao ◽  
Ming Liu
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh ◽  
Moment Coefficient ◽  
Mesh Model ◽  
Fluent Software

In this paper, using sliding mesh model, the numerical simulation of small vertical axis wind turbine aerodynamic performance was studied with FLUENT software. Got change rule of four same thickness and different camber‘s NACA series asymmetrical airfoil moment coefficient of the wind turbine and wind power machine with the tip speed ratio. Wind turbine benchmark blade around the flow field was studied. Research shows that within a certain range, small vertical axis wind turbine aerodynamic performance be promoted if the airfoil relative thickness increases. In the case of large attack angle, the wind turbine blade is easy to be separated. It provides a theoretical reference for optimal design of a small vertical axis wind turbine.

scholarly journals Proposal of a Nature-Inspired Shape for a Vertical Axis Wind Turbine and Comparison of Its Performance with a Semicircular Blade Profile

2021 ◽  
Vol 11 (13) ◽  
pp. 6198
Author(s):  
Javier Blanco ◽  
Juan de Dios Rodriguez ◽  
Antonio Couce ◽  
Maria Isabel Lamas
Keyword(s):  
Numerical Model ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Experimental Model ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Cfd Model ◽  
Blade Profile ◽  
Vertical Axis Wind Turbine

In order to improve the efficiency of the Savonius type vertical axis wind turbine, the present work analyzes an improvement based on an innovative rotor geometry. The rotor blades are inspired on an organic shape mathematically analyzed, the Fibonacci’s spiral, presented in many nature systems as well as in art. This rotor was analyzed in a wind tunnel and through a CFD model. The power coefficients at different tip speed ratios (TSR) were characterized and compared for the Savonius turbine and two versions using the Fibonacci’s spiral. One of the proposed geometries improves the performance of the Savonius type. Particularly, the optimal configuration lead to an improvement in maximum power coefficient of 14.5% in the numerical model respect to a conventional Savonius turbine and 17.6% in the experimental model.

Calculating the aerodynamics of vertical axis wind turbines

2012 ◽  
Vol 34 (3) ◽  
pp. 169-184 ◽  
Author(s):  
Hoang Thi Bich Ngoc
Keyword(s):  
Wind Turbine ◽  
Incidence Angle ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Velocity Triangle ◽  
Relationship Of ◽  
The Relationship

Vertical axis wind turbine technology has been applied last years, very long after horizontal axis wind turbine technology. Aerodynamic problems of vertical axis wind machines are discussible. An important problem is the determination of the incidence law in the interaction between wind and rotor blades. The focus of the work is to establish equations of the incidence depending on the blade azimuth, and to solve them. From these results, aerodynamic torques and power can be calculated. The incidence angle is a parameter of velocity triangle, and both the factors depend not only on the blade azimuth but also on the ratio of rotational speed and horizontal speed. The built computational program allows theoretically selecting the relationship of geometric parameters of wind turbine in accordance with requirements on power, wind speed and installation conditions.

Aerodynamic and aeroacoustic performance investigations on modified H-rotor Darrieus wind turbine

2021 ◽  
pp. 0309524X2110039
Author(s):  
Amgad Dessoky ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Wind Turbine ◽  
High Speed ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
3D Models ◽  
Power Coefficient ◽  
Design Parameters ◽  
Second Phase ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes

The present paper investigates the aerodynamic and aeroacoustic characteristics of the H-rotor Darrieus vertical axis wind turbine (VAWT) combined with very promising energy conversion and steering technology; a fixed guide-vanes. The main scope of the current work is to enhance the aerodynamic performance and assess the noise production accomplished with such enhancement. The studies are carried out in two phases; the first phase is a parametric 2D CFD simulation employing the unsteady Reynolds-averaged Navier-Stokes (URANS) approach to optimize the design parameters of the guide-vanes. The second phase is a 3D CFD simulation of the full turbine using a higher-order numerical scheme and a hybrid RANS/LES (DDES) method. The guide-vanes show a superior power augmentation, about 42% increase in the power coefficient at λ = 2.75, with a slightly noisy operation and completely change the signal directivity. A remarkable difference in power coefficient is observed between 2D and 3D models at the high-speed ratios stems from the 3D effect. As a result, a 3D simulation of the capped Darrieus turbine is carried out, and then a noise assessment of such configuration is assessed. The results show a 20% increase in power coefficient by using the cap, without significant change in the noise signal.

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