Numerical Implications of Solidity and Blade Number on Rotor Performance of Horizontal-Axis Wind Turbines

2003 ◽  
Vol 125 (4) ◽  
pp. 425-432 ◽  
Author(s):  
Matthew M. Duquette ◽  
Kenneth D. Visser
Keyword(s):  
Wind Turbines ◽  
High Speed ◽  
Numerical Study ◽  
Power Extraction ◽  
Blade Number ◽  
Small Wind Turbines ◽  
Horizontal Axis Wind Turbines ◽  
The Impact ◽  
Lifting Line ◽  
System Power

A numerical study was conducted to examine the impact of rotor solidity and blade number on the aerodynamic performance of small wind turbines. Blade element momentum theory and lifting line based wake theory were utilized to parametrically assess the effects of blade number and solidity on rotor performance. Increasing the solidity beyond what is traditionally used for electric generating wind turbines led to increased power coefficients at lower tip speed ratios, with an optimum between 3 and 4. An increase in the blade number at a given solidity also increased the maximum Cp for all cases examined. The possibility of a higher aerodynamic power extraction from solidity or blade number increases could lead to a higher overall system power production. Additional advantages over current 5% to 7% solidity, high speed designs would include lower noise, lower cut-in wind speed, and less blade erosion.

Experimental and numerical investigation of novel Savonius wind turbine

2018 ◽  
Vol 43 (3) ◽  
pp. 247-262 ◽  
Author(s):  
Palanisamy Mohan Kumar ◽  
M Mohan Ram Surya ◽  
Srikanth Narasimalu ◽  
Teik-Cheng Lim
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
High Speed ◽  
Large Scale ◽  
Numerical Study ◽  
Low Noise ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Horizontal Axis Wind Turbines ◽  
Thrust Load

Savonius wind turbines have distinct advantages in terms of simplicity, low noise, and ease of manufacturing, yet they are not preferred for large-scale power generation due to their lower aerodynamic performance and high wind loads. This study is aimed at reducing the thrust load with retractable type telescopic blades. This novel telescopic Savonius turbine is tested in an open jet wind tunnel to assess the performance in terms of torque, power, and thrust on the rotor. The dynamic and static characteristics are obtained for both extended and retracted configuration after correcting the experimental data for wind tunnel blockage. A preliminary numerical study is carried out in an effort to determine the variation of the drag coefficient in relation to the bucket thickness. The proposed telescopic turbine demonstrates a reduction in thrust load of 72.4% with a maximum power coefficient of 0.14 at the tip speed ratio of 0.7 compared to an extended operating configuration, similar to a conventional Savonius turbine. Thus, the telescopic Savonius turbine can be scaled up to higher kilowatt capacity with the cost comparable to other high-speed rotors such as Darrieus or horizontal axis wind turbines.

Small Wind Turbines in the Built Environment: Influence of Flow Inclination on the Potential Energy Yield

2013 ◽  
Author(s):  
Serena Bianchi ◽  
Alessandro Bianchini ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari
Keyword(s):  
Built Environment ◽  
Potential Energy ◽  
Wind Turbines ◽  
Local Governments ◽  
Energy Yield ◽  
Simulation Code ◽  
Specific Flow ◽  
Small Wind Turbines ◽  
Horizontal Axis Wind Turbines ◽  
The Impact

Increasing interest is being paid by architects, project developers and local governments to understand where small wind turbines can effectively be exploited to provide delocalized power in the built environment. The wind conditions in the rooftop area of buildings in urban locations are, however, very complex and the real adaptability of wind turbines to these environments is not yet tested both in terms of real producibility and of structural compatibility with the building themselves. In these installations, in particular, the flow which incomes on the rotors is often inclined with respect to the horizontal direction due to the interaction with the building façade and the roof. A correct estimation of the impact of an inclined flow on the performance of horizontal-axis wind turbines therefore becomes a very relevant issue to correctly predict the potential energy yield of a machine. To this purpose, a simulation code based on a Blade Element Momentum (BEM) approach was developed and validated by means of experimental data found in the literature. The code was then used to evaluate the energetic suitability of a small-size wind turbine installation in the rooftop of a building in a conventional European city. A numerical CFD analysis was carried out to characterize the flow field in the rooftop area of different buildings. The flow velocity modulus and direction were calculated for several oncoming wind profiles: the results were projected into an available wind power curve in the rooftop of the building. The effective energy-yield capabilities were then corrected using the model for the flow inclination as a function of the specific flow conditions in the rooftop area. The results were finally exploited to analyze the energy-oriented feasibility of an installation in a similar context.

Small Wind Turbines in the Built Environment: Influence of Flow Inclination on the Potential Energy Yield

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Serena Bianchi ◽  
Alessandro Bianchini ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari
Keyword(s):  
Built Environment ◽  
Potential Energy ◽  
Wind Turbines ◽  
Local Governments ◽  
Energy Yield ◽  
Simulation Code ◽  
Specific Flow ◽  
Small Wind Turbines ◽  
Horizontal Axis Wind Turbines ◽  
The Impact

Increasing interest is being paid by architects, project developers and local governments to understanding where small wind turbines can effectively be exploited to provide delocalized power in the built environment. The wind conditions in the rooftop area of buildings in urban locations are, however, very complex and the real adaptability of wind turbines to these environments is not yet tested both in terms of real producibility and of structural compatibility with the building themselves. In these installations, in particular, the flow that incomes on the rotor is often inclined with respect to the horizontal direction due to the interaction with the building façade and the roof. A correct estimation of the impact of an inclined flow on the performance of horizontal-axis wind turbines, therefore, becomes a very relevant issue to correctly predict the potential energy yield of a machine. To this purpose, a simulation code based on a blade element momentum (BEM) approach was developed and validated by means of experimental data found in the literature. The code was then used to evaluate the energetic suitability of a small-size wind turbine installation in the rooftop of a building in a conventional European city. A numerical computational fluid dynamics (CFD) analysis was carried out to characterize the flow field in the rooftop area of different buildings. The flow velocity modulus and direction were calculated for several oncoming wind profiles: The results were projected into an available wind power curve in the rooftop of the building. The effective energy-yield capabilities were then corrected using the model for the flow inclination as a function of the specific flow conditions in the rooftop area. The results were finally exploited to analyze the energy-oriented feasibility of an installation in a similar context.

A comprehensive comparative investigation of the Lifting Line Theory and Blade Element Momentum Theory applied to small wind turbines

2021 ◽  
pp. 1-25
Author(s):  
K.A.R. Ismail ◽  
Willian Okita
Keyword(s):  
Wind Turbines ◽  
Power Coefficient ◽  
Computational Time ◽  
Local Flow ◽  
Small Wind Turbines ◽  
Wake Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

Abstract Small wind turbines are adequate for electricity generation in isolated areas to promote local expansion of commercial activities and social inclusion. Blade element momentum (BEM) method is usually used for performance prediction, but generally produces overestimated predictions since the wake effects are not precisely accounted for. Lifting line theory (LLT) can represent the blade and wake effects more precisely. In the present investigation the two methods are analyzed and their predictions of the aerodynamic performance of small wind turbines are compared. Conducted simulations showed a computational time of about 149.32 s for the Gottingen GO 398 based rotor simulated by the BEM and 1007.7 s for simulation by the LLT. The analysis of the power coefficient showed a maximum difference between the predictions of the two methods of about 4.4% in the case of Gottingen GO 398 airfoil based rotor and 6.3% for simulations of the Joukowski J 0021 airfoil. In the case of the annual energy production a difference of 2.35% is found between the predictions of the two methods. The effects of the blade geometrical variants such as twist angle and chord distributions increase the numerical deviations between the two methods due to the big number of iterations in the case of LLT. The cases analyzed showed deviations between 3.4% and 4.1%. As a whole, the results showed good performance of both methods; however the lifting line theory provides more precise results and more information on the local flow over the rotor blades.

Influence of Wave Shape on the Impact of Shallow-Water Waves on Vertical Walls

2006 ◽  
Author(s):  
Claudio Zanzi ◽  
Pablo Go´mez ◽  
Julia´n Palacios ◽  
Joaqui´n Lo´pez ◽  
Julio Herna´ndez
Keyword(s):  
Shallow Water ◽  
Level Set ◽  
Water Waves ◽  
High Speed ◽  
Numerical Study ◽  
Local Level ◽  
Wave Shape ◽  
Shallow Water Waves ◽  
Vertical Walls ◽  
The Impact

A numerical study of the impact of shallow-water waves on vertical walls is presented. The air-liquid flow was simulated using a code for incompressible viscous flow, based on a local level set algorithm and a second-order approximate projection method. The level set transport and reinitialization equations were solved in a narrow band around the interface using an adaptive refined grid. The wave is assumed to be generated by a plunger which is accelerated in an open channel containing water. An arbitrary Lagrangian-Eulerian method was used to take into account the relative movement between the plunger and the end wall of the channel. The evolution of the free surface was visualized using a laser light sheet and a high-speed camera, with a sampling frequency of 1000 Hz. Several simulations were carried out to investigate the influence of the shape of the wave approaching the wall on the relevant quantities associated with the impact. The wave shape just before the impact was changed varying the total length of the channel. The results are compared with experimental results and with results obtained by other authors.

Lifting Line Free Wake Vortex Filament Method for the Evaluation of Floating Offshore Wind Turbines: First Step — Validation for Fixed Wind Turbines

2019 ◽  
Author(s):  
Raquel Martín-San-Román ◽  
José Azcona-Armendáriz ◽  
Alvaro Cuerva-Tejero
Keyword(s):  
Wind Turbines ◽  
Vortex Filament ◽  
Offshore Wind ◽  
Critical Parameters ◽  
Aerodynamic Model ◽  
Floating Offshore Wind Turbines ◽  
Free Wake ◽  
The Impact ◽  
Lifting Line ◽  
Vortex Filament Method

Abstract An in-house computational tool, called MIST, has been developed to improve the accuracy of the aerodynamic loads predictions of floating wind turbines. MIST has an aerodynamic module based on a Free Vortex filament Method (FVM) for the wake combined with a Lifting Line (LL) model for the blades. This aerodynamic model has been validated, in this first instance, for an onshore configuration against well known experimental data. Different options for the critical parameters of the code have been analyzed to get a deeper understanding of the impact of certain assumptions of this kind of models.

Development and Application of a Simulation Tool for Vertical and Horizontal Axis Wind Turbines

2013 ◽  
Author(s):  
David Marten ◽  
Juliane Wendler ◽  
Georgios Pechlivanoglou ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Horizontal Axis ◽  
Vertical Axis Wind Turbine ◽  
First Case ◽  
Horizontal Axis Wind Turbines ◽  
Lift And Drag ◽  
The Impact

A double-multiple-streamtube vertical axis wind turbine simulation and design module has been integrated within the open-source wind turbine simulator QBlade. QBlade also contains the XFOIL airfoil analysis functionalities, which makes the software a single tool that comprises all functionality needed for the design and simulation of vertical or horizontal axis wind turbines. The functionality includes two dimensional airfoil design and analysis, lift and drag polar extrapolation, rotor blade design and wind turbine performance simulation. The QBlade software also inherits a generator module, pitch and rotational speed controllers, geometry export functionality and the simulation of rotor characteristics maps. Besides that, QBlade serves as a tool to compare different blade designs and their performance and to thoroughly investigate the distribution of all relevant variables along the rotor in an included post processor. The benefits of this code will be illustrated with two different case studies. The first case deals with the effect of stall delaying vortex generators on a vertical axis wind turbine rotor. The second case outlines the impact of helical blades and blade number on the time varying loads of a vertical axis wind turbine.

Computational Investigation of a Shrouded Vertical Axis Wind Turbine

2016 ◽  
Author(s):  
K. Vafiadis ◽  
H. Fintikakis ◽  
I. Zaproudis ◽  
A. Tourlidakis
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Urban Areas ◽  
Numerical Study ◽  
Flow Analysis ◽  
Vertical Axis ◽  
Green Energy ◽  
Vertical Axis Wind Turbine ◽  
Wide Range ◽  
Small Wind Turbines

In urban areas, it is preferable to use small wind turbines which may be integrated to a building in order to supply the local grid with green energy. The main drawback of using wind turbines in urban areas is that the air flow is affected by the existence of nearby buildings, which in conjunction with the variation of wind speed, wind direction and turbulence may adversely affect wind energy extraction. Moreover, the efficiency of a wind turbine is limited by the Betz limit. One of the methods developed to increase the efficiency of small wind turbines and to overcome the Betz limit is the introduction of a converging – diverging shroud around the turbine. Several researchers have studied the effect of shrouds on Horizontal Axis Wind Turbines, but relatively little research has been carried out on shroud augmented Vertical Axis Wind Turbines. This paper presents the numerical study of a shrouded Vertical Axis Wind Turbine. A wide range of test cases, were examined in order to predict the flow characteristics around the rotor, through the shroud and through the rotor – shroud arrangement using 3D Computational Fluid Dynamics simulations. The power output of the shrouded rotor has been improved by a factor greater than 2.0. The detailed flow analysis results showed that there is a significant improvement in the performance of the wind turbine.

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