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.

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.

Performance Improvements for a Vertical Axis Wind Turbine by Means of Gurney Flap

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Yan Yan ◽  
Eldad Avital ◽  
John Williams ◽  
Jiahuan Cui
Keyword(s):  
Wind Turbine ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Performance Improvements ◽  
Gurney Flap

Abstract A numerical study was carried out to investigate the effects of a Gurney flap (GF) on the aerodynamics performance of the NACA 00 aerofoil and an associated three-blade rotor of a H-type Darrieus wind turbine. The flow fields around a single aerofoil and the vertical axis wind turbine (VAWT) rotor are studied using unsteady Reynolds-averaged Navier–Stokes equations (URANS). The height of GF ranges from 1% to 5% of the aerofoil chord length. The results show that the GF can increase the lift and lift-to-drag ratio of the aerofoil as associated with the generation of additional vortices near the aerofoil trailing edge. As a result, adding a GF can significantly improve the power coefficient of the VAWT at low tip speed ratio (TSR), where it typically gives low power production. The causing mechanism is discussed in detail, pointing to flow separation and dynamic stall delay.

Numerical Study of Pitch Angle on H-Type Vertical Axis Wind Turbine

2012 ◽  
Vol 499 ◽  
pp. 259-264
Author(s):  
Qi Yao ◽  
Ying Xue Yao ◽  
Liang Zhou ◽  
S.Y. Zheng
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Vertical Axis ◽  
Azimuth Angle ◽  
Power Coefficient ◽  
Cfd Model ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh ◽  
Mesh Technique

This paper presents a simulation study of an H-type vertical axis wind turbine. Two dimensional CFD model using sliding mesh technique was generated to help understand aerodynamics performance of this wind turbine. The effect of the pith angle on H-type vertical axis wind turbine was studied based on the computational model. As a result, this wind turbine could get the maximum power coefficient when pitch angle adjusted to a suited angle, furthermore, the effects of pitch angle and azimuth angle on single blade were investigated. The results will provide theoretical supports on study of variable pitch of wind turbine.

scholarly journals Vertical-axis wind-turbine computations using a 2D hybrid wake actuator-cylinder model

2021 ◽  
Vol 6 (4) ◽  
pp. 1061-1077
Author(s):  
Edgar Martinez-Ojeda ◽  
Francisco Javier Solorio Ordaz ◽  
Mihir Sen
Keyword(s):  
Wind Turbine ◽  
Hollow Cylinder ◽  
Stokes Equations ◽  
Finite Thickness ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Computational Domain ◽  
Source Terms ◽  
Vertical Axis Wind Turbine ◽  
Cylinder Model

Abstract. The actuator-cylinder model was implemented in OpenFOAM by virtue of source terms in the Navier–Stokes equations. Since the stand-alone actuator cylinder is not able to properly model the wake of a vertical-axis wind turbine, the steady incompressible flow solver simpleFoam provided by OpenFOAM was used to resolve the entire flow and wakes of the turbines. The source terms are only applied inside a certain region of the computational domain, namely a finite-thickness cylinder which represents the flight path of the blades. One of the major advantages of this approach is its implicitness – that is, the velocities inside the hollow cylinder region feed the stand-alone actuator-cylinder model (AC); this in turn computes the volumetric forces and passes them to the OpenFOAM solver in order to be applied inside the hollow cylinder region. The process is repeated in each iteration of the solver until convergence is achieved. The model was compared against experimental works; wake deficits and power coefficients are used in order to assess the validity of the model. Overall, there is a good agreement of the pattern of the power coefficients according to the positions of the turbines in the array. The actual accuracy of the power coefficient depends strongly on the solidity of the turbine (actuator cylinder related) and both the inlet boundary turbulence intensity and turbulence length scale (RANS simulation related).

scholarly journals NUMERICAL STUDY OF TWO VERTICAL AXIS WIND TURBINES DARRIEU TYPE LINED UP IN FUNCTION OF POWER COEFFICIENT1

2017 ◽  
Vol 6 (3) ◽  
Author(s):  
Rodrigo Spotorno Vieira ◽  
Luiz Alberto Oliveira Rocha ◽  
Liércio André Isoldi ◽  
Elizaldo Domingues Dos Santos
Keyword(s):  
Wind Turbine ◽  
Numerical Study ◽  
Mass Conservation ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Worst Case ◽  
Study Power ◽  
Great Possibility ◽  
Volume Method

In this work is performed a numerical study of the main operational principle of a VAWT (Vertical Axis Wind turbine) and the influence of the distance between two aligned turbines over their power coefficient. The main aims here are to evaluate the applicability of the numerical model studied here in further optimization studies of VAWT and evaluate the effect of the distance between turbines (d) on the device power coefficient. To achieve these goals, it is considered an incompressible, transient and turbulent flow on a two dimensional domain with two fluid zones, one being rotational representing the rotation of the blades. The time-averaged mass conservation equations and momentum are numerically solved using the finite volume method, more precisely with the software FLUENTÒ. For the approach of turbulence is used to classical modeling of turbulence (RANS) with standard model k - ε. Other geometric parameters: turbine radius (R), the airfoil profile (NACA0018) and chorus were held constant. The verification results showed a good agreement with those presented in the literature, even employing a simplified domain. It was also observed that the distance (d) directly affects the power of the second turbine. For the best case, with d =10m, the downstream turbine showed an approximate 50% drop in power coefficient in comparison with that obtained for the upstream turbine. While in the worst case, with d =2m, the power coefficient for the downstream turbine decreased two hundred times in comparison with that achieved for the upstream one. It was also noted that there is a great possibility of disposal area optimization of turbines in future studies. Keywords: Vertical Axis Wind turbine, Numerical study, Power coefficient, turbine distance.

CFD Sensitivity Analysis of a Straight-Blade Vertical Axis Wind Turbine

2012 ◽  
Vol 36 (5) ◽  
pp. 571-588 ◽  
Author(s):  
Khaled M Almohammadi ◽  
D B Ingham ◽  
L Ma ◽  
M Pourkashanian
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Wind Turbine ◽  
Turbulence Intensity ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Computational Domain ◽  
Vertical Axis Wind Turbine ◽  
Airfoil Surface ◽  
Straight Blade

This paper investigates the flow field features and the predicted power coefficient of a straight blade vertical axis wind turbine (SB-VAWT) using computational fluid dynamics modeling using 2D simulations. The Unsteady Navier-Stokes equations are solved with the concept of Reynolds averaging using the commercial software FLUENT and the sliding mesh technique is applied. In the mesh phase, three parameters have been investigated, namely the cell type, the cell aspect ratio on the airfoil surface, and the total number of cells in the computational domain. In the simulation phase, two parameters have been investigated, namely the time step/Courant number, and the turbulence intensity. Significant differences have been observed in the flow field features and on the predicted power coefficient for some of these parameters which if not considered in details could lead to unreliable predictions. The sensitivity of the parameters is not equally significant and this paper suggests which parameters should be focused on in the modeling process. The convergence behavior of the quadrilateral based mesh is found to be more consistent compared to the triangular based mesh. In the mesh phase, the cell aspect ratio on the airfoil surface was found to be a significant factor, whereas the turbulence intensity was found to be a significant fac-tor in the simulation phase.

Numerical Investigation of a Vertical Axis Wind Turbine Performance Characterization Using New Variable Pitch Control Scheme

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Amin A. Mohammed ◽  
Ahmet Z. Sahin ◽  
Hassen M. Ouakad
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Average Power ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Variable Pitch ◽  
De Algorithm

Abstract A double multiple streamtube model coupled with variable pitch methodology is used to analyze the performance characteristics of a small-scale straight-bladed Darrieus type vertical axis wind turbine (SB-VAWT). The numerical study revealed that a fixed pitch of −2.5 deg could greatly enhance the performance of the wind turbine. However, no improvement is observed in the starting torque capacity. Furthermore, the performance of upwind and downwind zones has been investigated, and it is found that the VAWT starting capacity is improved by increasing/decreasing the pitch angle upwind/downwind of the turbine. To optimize the performance, four cases of variable pitch angle schemes of sinusoidal nature were examined. The parameters of the sinusoidal functions were optimized using differential evolution (DE) algorithm with different cost functions. The results showed improvement in the power coefficient, yet with low starting capacity enhancement. Among the objective functions used in DE algorithm, the negative of the average power coefficient is found to lead to the best starting capacity with moderate peak power coefficient.

1218 Numerical Analysis about the Optimal Dimension of Endplates of Straight-Blade Vertical Axis Wind Turbine

2016 ◽  
Vol 2016.54 (0) ◽  
pp. _1218-1_-_1218-2_
Author(s):  
Yutaka HARA ◽  
Yuuki FURUKAWA ◽  
Takahiro SUMI ◽  
Hiromichi AKIMOTO ◽  
Shigeo YOSHIDA
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Optimal Dimension ◽  
Straight Blade

A Numerical Study on the Effects of Unsteady Wind on Vertical Axis Wind Turbine Performance

2013 ◽  
Author(s):  
Louis Angelo Danao ◽  
Jonathan Edwards ◽  
Okeoghene Eboibi ◽  
Robert Howell
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Peak Performance ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio

Numerical simulations using RANS–based CFD have been utilised to carry out investigations on the effects of unsteady wind in the performance of a wind tunnel vertical axis wind turbine. Using a validated CFD model, unsteady wind simulations revealed a fundamental relationship between instantaneous VAWT CP and wind speed. CFD data shows a CP variation in unsteady wind that cuts across the steady CP curve as wind speed fluctuates. A reference case with mean wind speed of 7m/s, wind speed amplitude of ±12%, fluctuating frequency of 0.5Hz and mean tip speed ratio of 4.4 has shown a wind cycle mean power coefficient of 0.33 that equals the steady wind maximum. Increasing wind speed causes the instantaneous tip speed ratio to fall which leads to higher effective angle of attack and deeper stalling on the blades. Stalled flow and rapid changes in angle of attack of the blade induce hysteresis loops in both lift and drag. Decreasing wind speeds limit the perceived angle of attack seen by the blades to near static stall thus reducing the positive effect of dynamic stall on lift generation. Three mean tip speed ratio cases were tested to study the effects of varying conditions of VAWT operation on the overall performance. As the mean tip speed ratio increases, the peak performance also increases.

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