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.

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.

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.

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.

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.

Numerical Study to Quantify the Effects of Struts and Central Hub on the Performance of a Three Dimensional Vertical Axis Wind Turbine Using Sliding Mesh

2013 ◽  
Author(s):  
M. Salman Siddiqui ◽  
Naveed Durrani ◽  
Imran Akhtar
Keyword(s):  
Wind Turbine ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Unit Length ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Torque Ripple ◽  
Outer Diameter ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh

A computational fluid dynamic (CFD) analysis is carried out to investigate the effects of struts and central hub in 3D on the overall performance prediction of a three dimensional vertical axis wind turbine (VAWT) with three Darrieus H-type blades. The VAWT has the outer diameter of 2.5m and finite unit length height with expected output of 2KVA. This type of small VAWT are expected to perform better on roof tops of the built-up urban area. The analysis is carried out using sliding mesh concept in commercial CFD software ‘Ansys Fluent 13’. It is observed that the struts and central hub assembly induce additional drag and generate strong vortices which caused a substantial decrease in the performance parameters of the turbine. The numerical simulation are carried out over a three dimensional VAWT with and without struts and central hub. It is found that both the cases show a similar trend of the torque ripple for any one blade while for the upstream path, on the contrary the blades experience a drop in performance from 220° to 360° due to the struts and central hub assembly. A detailed comparative analysis between both the cases is made over the TSR values range from 1.5 to 4.5. At TSR = 1.5, the performance coefficient of the cases with and without struts and central hub are same. However, for the case of struts and central hub, TSR 4 and above show negative values of power coefficients.

scholarly journals Computational fluid dynamic (CFD) of vertical-axis wind turbine: mesh and time-step sensitivity study

2019 ◽  
Vol 13 (3) ◽  
pp. 5604-5624
Author(s):  
S. Ashwindran ◽  
A. A. Azizuddin ◽  
A. N. Oumer
Keyword(s):  
Wind Turbine ◽  
Numerical Study ◽  
Computational Cost ◽  
Vertical Axis ◽  
Sensitivity Study ◽  
Dynamic Mode ◽  
Vertical Axis Wind Turbine ◽  
Time Step ◽  
Sliding Mesh ◽  
Mesh Resolution

This paper presents mesh and time-step dependence study of newly designed drag type vertical axis wind turbine. Ansys FLUENT a commercially available CFD solver was used to perform CFD numerical study on the drag type wind turbine. In computational analysis, 2D models was simulated under unsteady flow fields using SST k-ω to achieve stabilized numerical convergence. The model was analyzed at static and dynamic mode, where sliding mesh technique was used to analyze the turbine in dynamic mode. Three main parameters were taken under careful consideration: mesh resolution, turbulence model and time-step. Aerodynamic force was used in mesh sensitivity study for both static and sliding mesh. A small discrepancy in results of 2D sliding mesh result at different time-step and mesh resolution was observed. The generated results showed good agreement between fine and medium mesh with small difference in the initial initialization. In time-step dependency study for static mesh, dt=0.0002 time-step size was chosen for economical computational cost.

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.

Aerodynamic Design Optimization of Elliptical-Bladed Savonius-Style Wind Turbine by Numerical Simulations

2016 ◽  
Author(s):  
Nur Alom ◽  
Satish Chandra Kolaparthi ◽  
Sarath Chandra Gadde ◽  
Ujjwal K. Saha
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Numerical Study ◽  
Low Cost ◽  
Vertical Axis ◽  
3D Simulation ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Savonius-style wind turbine (SSWT), a class of vertical-axis wind turbine, appears to be promising for off-shore applications because of its design simplicity, good starting ability, insensitivity to wind direction, relatively low operating speed, low cost and easy installation. Various blade shapes have been used over the years to improve the performance of this class of turbine. In the recent past, an elliptic-bladed profile with sectional cut angle of 50° has shown its potential to harness the wind energy more efficiently. The present study aims to optimize this profile by numerical simulations. In view of this, the elliptical-bladed profiles are tested at different sectional cut angles of θ = 45°, 47.5°, 50° and 55°. The shear stress transport (SST) k-ω turbulence model is used to simulate the flow field, and thereafter, the torque and power coefficients are obtained at the rotating conditions. From 2D simulation, pressure and velocity contours are generated and analyzed. 2D simulations are also carried out for a semi-circular bladed profile in order to have a direct comparison. The numerical study demonstrates an improved flow characteristics, and hence the power coefficient of the elliptical-bladed profile at = 47.5°. Finally, 3D simulation is carried out to visualize and analyze the flow field around the optimum elliptical-bladed rotor at a tip speed ratio of 0.8. The aspect ratio of the rotor for the 3D simulation is kept at 0.7.

Analysis for 2D Flow Field around H-Vertical Axis Wind Turbine with Different Types of Airfoil

2012 ◽  
Vol 562-564 ◽  
pp. 1197-1200
Author(s):  
Tao Ye ◽  
Meng Liu
Keyword(s):  
Wind Turbine ◽  
Pressure Field ◽  
Vertical Axis ◽  
Cfd Model ◽  
Vertical Axis Wind Turbine ◽  
Different Types ◽  
2D Flow ◽  
Wind Turbine Airfoil ◽  
Turbulent Models ◽  
Mesh Technique

In this study, moving mesh technique is used to construct an outside flow CFD model around H-vertical axis wind turbine with different types of airfoil. RNG turbulent models and the implicit Couple arithmetic based on pressure are selected to solve the transient equation. From the results of the calculation, the author obtains the velocity field, pressure field distribution of H-type vertical axis wind turbine airfoil at different moments and analyze the wind wheel blade torque variation. The conclusion provides the theoretical basis and a method to optimize aerodynamic performance for the further study of vertical axis wind turbine in the future.

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.

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