CFD Calculation of Wind Turbines Power Variations in Urban Areas

2012 ◽  
Vol 622-623 ◽  
pp. 1084-1088
Author(s):  
Jafar Bazrafshan ◽  
Payam Sabaeifard ◽  
Farid Khalafi ◽  
Majid Jamil
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Urban Areas ◽  
Stokes Equations ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Navier Stokes Equations ◽  
Cfd Method

Integrating wind turbines in urban areas especially over buildings is a new way of producing electricity which is supported in recent years. Wind turbines sited well above the roof of buildings operate in skewed flow. In this paper, to examine variations in efficiency of wind turbines in this condition, two models of H-Rotor and horizontal axis wind turbine analyzed based on axial momentum theory through computer simulations. Simulations conducted through CFD method and k-ε turbulence model was utilized to analyze flow fluctuations in Navier-Stokes equations. Models show that, for an H-Rotor, the optimal power output in tilted flow can be up to two times the power output of horizontal axis wind turbine (HAWT).

Analysis of Unsteady Flows Past Horizontal Axis Wind Turbine Airfoils Based on Harmonic Balance Compressible Navier-Stokes Equations With Low-Speed Preconditioning

2011 ◽  
Author(s):  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Harmonic Balance ◽  
Stokes Equations ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Low Speed ◽  
Computational Performance

This paper presents the numerical models underlying the implementation of a novel harmonic balance compressible Navier-Stokes solver with low-speed preconditioning for wind turbine unsteady aerodynamics. The numerical integration of the harmonic balance equations is based on a multigrid iteration, and, for the first time, a numerical instability associated with the use of such an explicit approach in this context is discussed and resolved. The harmonic balance solver with low-speed preconditioning is well suited for the analyses of several unsteady periodic low-speed flows, such as those encountered in horizontal axis wind turbines. The computational performance and the accuracy of the technology being developed are assessed by computing the flow field past two sections of a wind turbine blade in yawed wind with both the time- and frequency-domain solvers. Results highlight that the harmonic balance solver can compute these periodic flows more than 10 times faster than its time-domain counterpart, and with an accuracy comparable to that of the time-domain solver.

scholarly journals Analysis of Unsteady Flows Past Horizontal Axis Wind Turbine Airfoils Based on Harmonic Balance Compressible Navier-Stokes Equations With Low-Speed Preconditioning

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Harmonic Balance ◽  
Stokes Equations ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Low Speed ◽  
Computational Performance

This paper presents the numerical models underlying the implementation of a novel harmonic balance compressible Navier-Stokes solver with low-speed preconditioning for wind turbine unsteady aerodynamics. The numerical integration of the harmonic balance equations is based on a multigrid iteration, and, for the first time, a numerical instability associated with the use of such an explicit approach in this context is discussed and resolved. The harmonic balance solver with low-speed preconditioning is well suited for the analyses of several unsteady periodic low-speed flows, such as those encountered in horizontal axis wind turbines. The computational performance and the accuracy of the technology being developed are assessed by computing the flow field past two sections of a wind turbine blade in yawed wind with both the time-and frequency-domain solvers. Results highlight that the harmonic balance solver can compute these periodic flows more than 10 times faster than its time-domain counterpart, and with an accuracy comparable to that of the time-domain solver.

Turbulent Unsteady Flow Analysis of Horizontal Axis Wind Turbine Airfoil Aerodynamics Based on the Harmonic Balance Reynolds-Averaged Navier-Stokes Equations

2014 ◽  
Author(s):  
M. Sergio Campobasso ◽  
Fabio Gigante ◽  
Jernej Drofelnik
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Harmonic Balance ◽  
Stokes Equations ◽  
Transport Model ◽  
Flow Analysis ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Reynolds Averaged Navier Stokes

Several horizontal axis wind turbine unsteady flows, such as that associated with the yawed wind regime, are predominantly periodic. Harmonic balance Reynolds-averaged Navier-Stokes solvers can be used to accurately analyze such flows substantially faster than what their time-domain counterparts can do. The paper presents the mathematical and numerical features of a new turbulent harmonic balance Navier-Stokes solver using Menter’s shear stress transport model for the turbulence closure. The effectiveness of the developed technology is demonstrated by using two-dimensional harmonic balance flow simulations to determine the periodic aerodynamic loads acting on a blade section of a 164 m-diameter wind turbine rotor in yawed wind. Presented results highlight that the turbulent harmonic balance solver can compute the sectional hysteresis force cycles more than 10 times faster than its time-domain counterpart, and with an accuracy comparable to that of the time-domain solver.

Wake Comparison of Open and Ducted Wind Turbines Using Actuator Disc Simulations

2020 ◽  
Author(s):  
Nojan Bagheri-Sadeghi ◽  
Brian T. Helenbrook ◽  
Kenneth D. Visser
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Turbulence Intensity ◽  
Stokes Equations ◽  
Rotor Blades ◽  
Energy Output ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Actuator Disc ◽  
Power And Energy

Abstract Shrouding a wind turbine inside a duct can significantly augment its power and energy output by increasing the mass flow rate through the rotor and decreasing the cut-in speed. Whether this is an advantage in a turbine array depends on the wake recovery behavior and how this compares to open wind turbines. Axisymmetric CFD simulations using the Reynolds-Averaged Navier-Stokes equations with a k–ω SST turbulence closure were used to compare the wake behavior of open and ducted wind turbines. For both cases, the rotor blades were modeled using an actuator disc. Simulations of open wind turbines revealed significant sensitivity of the wake behavior to the mean turbulence intensity at the rotor. Better agreement with experimental data for the far wake was obtained when the turbulence intensity at the rotor was comparable to values measured experimentally. It was observed that compared to an open wind turbine with similar power output, a DWT has a significantly slower wake recovery. This was attributed to the extra momentum deficit of the wake due to the drag force on the duct.

Wind Turbines Operating in Cold Climates: Reynolds Number and Turbulence Effects on Performances

2002 ◽  
Author(s):  
Nathalie Dabin ◽  
Christophe Leclerc ◽  
Christian Masson ◽  
Cedric Alinot
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Turbulence Intensity ◽  
Power Output ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Disk Model ◽  
Blade Element Theory ◽  
Turbulence Effects

The present study is motivated by several observations of unexpected, recurring, high levels of power for stall-regulated wind turbines operating under very low temperatures. As power levels recorded largely exceed design levels of the rotor, operation in such conditions can cause dramatic damage to turbine. This study aims to understand the origin of such phenomenon by analyzing experimental data gathered from a stall-controlled wind turbine, having a nominal power of more than 500 kW, and comparing the experimental behaviour with numerical simulations. To provide a quantitative estimate of density and atmospheric turbulence effects on power output, a procedure based on the IEC 61400-12 international standard for elaboration of a wind turbine power curve is used. The numerical simulations is based on the solution of the time-averaged, steady-state, incompressible Navier-Stokes equations with an appropriate turbulence closure model. The actuator disk model, together with blade element theory, are used to model the turbines. The stall-regulated turbine analyzed has shown to produce measured power increases significantly higher than increases of density. Regarding the influence of turbulence intensity, it has been observed that for constant hub height incoming wind velocity and density, power output increases with turbulence intensity at low winds, the opposite being true at higher winds. The numerical simulations show a good agrement with the measurements.

scholarly journals Canard optimization for enhancing the performance of small horizontal axis wind turbine at low wind speeds

2020 ◽  
Vol 37 ◽  
pp. 63-71
Author(s):  
Yui-Chuin Shiah ◽  
Chia Hsiang Chang ◽  
Yu-Jen Chen ◽  
Ankam Vinod Kumar Reddy
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Optimum Parameters ◽  
Low Wind Speeds

ABSTRACT Generally, the environmental wind speeds in urban areas are relatively low due to clustered buildings. At low wind speeds, an aerodynamic stall occurs near the blade roots of a horizontal axis wind turbine (HAWT), leading to decay of the power coefficient. The research targets to design canards with optimal parameters for a small-scale HAWT system operated at variable rotational speeds. The design was to enhance the performance by delaying the aerodynamic stall near blade roots of the HAWT to be operated at low wind speeds. For the optimal design of canards, flow fields of the sample blades with and without canards were both simulated and compared with the experimental data. With the verification of our simulations, Taguchi analyses were performed to seek the optimum parameters of canards. This study revealed that the peak performance of the optimized canard system operated at 540 rpm might be improved by ∼35%.

scholarly journals Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element

2021 ◽  
Vol 12 (1) ◽  
pp. 413
Author(s):  
Ibtissem Barkat ◽  
Abdelouahab Benretem ◽  
Fawaz Massouh ◽  
Issam Meghlaoui ◽  
Ahlem Chebel
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Vortex Method ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Good Representation ◽  
Horizontal Axis Wind Turbine ◽  
Blade Element

This article aims to study the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a turbine are controlled by the flow around the rotor, or estimate of air charges on the rotor blades under various operating conditions and their relation to the structural dynamics of the rotor are critical for design. One of the major challenges in wind turbine aerodynamics is to predict the forces on the blade as various methods, including blade element moment theory (BEM), the approach that is naturally adapted to the simulation of the aerodynamics of wind turbines and the dynamic and models (CFD) that describes with fidelity the flow around the rotor. In our article we proposed a modeling method and a simulation of the forces applied to the horizontal axis wind rotors turbines using the application of the blade elements method to model the rotor and the vortex method of free wake modeling in order to develop a rotor model, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of the aerodynamic loads exerted by the wind.

Nondimensional Parameters’ Effects on Hybrid Darrieus–Savonius Wind Turbine Performance

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Armin Roshan ◽  
Amir Sagharichi ◽  
Mohammad Javad Maghrebi
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Urban Areas ◽  
Model Performance ◽  
Vertical Axis ◽  
Favorable Effect ◽  
Turbine Performance ◽  
Primary Model ◽  
Overlap Ratio

Abstract Vertical axial wind turbines are the most commonly used turbines in residential and urban areas. This paper investigates the effect of combining Darrieus and Savonius wind turbines on power output and introduces a wind turbine with high starting torque addition to the wide working domain. A two-dimensional computational fluid dynamics transient simulation is developed, and a moving mesh is implemented for rotating moving parts. Comprehensive research has been carried out to investigate the effects of the initial overlap ratio (ɛ), arc angle Ø, and curvature (α) of Savonius blades on the performance of the turbine and 18 models are simulated at seven tip speed ratios. The results showed that combining the Darrieus turbine with the Savonius turbine has a favorable effect on self-starting performance. Also, it was observed that by changing each of the parameters, the primary model performance could be significantly improved. Finally, it is concluded that ɛ = 0.25, α = 0.25, and ∅ = 150 deg are the optimum values of the parameters which increase turbine power output compared to conventional vertical-axis turbines.

scholarly journals Comparison of horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT)

2018 ◽  
Vol 7 (4.13) ◽  
pp. 74 ◽  
Author(s):  
Muhd Khudri Johari ◽  
Muhammad Azim A Jalil ◽  
Mohammad Faizal Mohd Shariff
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Green Technology ◽  
Horizontal Axis ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Current Output ◽  
Voltage Output ◽  
And Performance

As the demand for green technology is rising rapidly worldwide, it is important that Malaysian researchers take advantage of Malaysia’s windy climates and areas to initiate more power generation projects using wind. The main objectives of this study are to build a functional wind turbine and to compare the performance of two types of design for wind turbine under different speeds and behaviours of the wind. A three-blade horizontal axis wind turbine (HAWT) and a Darrieus-type vertical axis wind turbine (VAWT) have been designed with CATIA software and constructed using a 3D-printing method. Both wind turbines have undergone series of tests before the voltage and current output from the wind turbines are collected. The result of the test is used to compare the performance of both wind turbines that will imply which design has the best efficiency and performance for Malaysia’s tropical climate. While HAWT can generate higher voltage (up to 8.99 V at one point), it decreases back to 0 V when the wind angle changes. VAWT, however, can generate lower voltage (1.4 V) but changes in the wind angle does not affect its voltage output at all. The analysis has proven that VAWT is significantly more efficient to be built and utilized for Malaysia’s tropical and windy climates. This is also an initiative project to gauge the possibility of building wind turbines, which could be built on the extensive and windy areas surrounding Malaysian airports.  

Effect of Blade Numbers on Pressure Drop of Axial Cyclone Separators by CFD

2011 ◽  
Vol 55-57 ◽  
pp. 343-347 ◽  
Author(s):  
Yi Gang Luan ◽  
Hai Ou Sun
Keyword(s):  
Pressure Drop ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Three Dimensional Model ◽  
Navier Stokes Equations ◽  
Pressure Drops ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Resistance Performance

In this article, computational fluid dynamics(CFD) method is used to predict the effect of blade numbers on the pressure drop of axial cyclone separators. A three-dimensional model is built to acquire the resistance of axial cyclone separators with different blade numbers. The flow field inside cyclone separators is calculated using 3D Reynolds-averaged Navier-Stokes equations. And turbulence model is used to simulate the Reynold stress. Also pressure drop of cyclone separators with different blade numbers is expressed as a function of different inlet velocities. At the same inlet velocity with increasing the blade numbers, pressure drops of cyclones reduce greatly. And changing the blade number of cyclone separator is an effective method to improve its resistance performance.

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