A comprehensive analysis of solidity for cambered darrieus VAWTs

Qamar, Sayyad Basim; Janajreh, Isam

doi:10.1016/j.ijhydene.2017.06.041

Cited by 40 publications

(24 citation statements)

References 31 publications

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“…Nevertheless, too much camber results in a worse performance of the turbine (for 6% camber the maximum power coefficient reached is below 0.5), confirming that unsymmetrical blades show a reduced peak efficiency compared to conventional symmetrical airfoils [28]. Therefore, from Figure 17 it may be deduced that the selection of the airfoil for a VAWT should lean towards symmetrical or lowcambered airfoils (camber less than 3%), as those will produce the highest power output (result similar to [34]). The use of greater camber values, however, would be justified for small VAWTs which otherwise would be unable to self-start (see the comments about the effect of the size of the turbine on its performance).…”

Section: Influence Of Cambermentioning

confidence: 69%

“…On the other hand, El-Samanoudy et al [31] and Jafaryar et al [32] claim that symmetrical or almost symmetrical airfoils perform better. Besides, as highlighted by Qamar and Janajreh [33], the literature does not show a comprehensive understanding of how solidity affects the performance of cambered VAWTs, especially with regard to the optimal configuration. These authors [34] found an improvement in the performance of VAWT at lower speeds using cambered blades.…”

mentioning

confidence: 99%

“…Besides, as highlighted by Qamar and Janajreh [33], the literature does not show a comprehensive understanding of how solidity affects the performance of cambered VAWTs, especially with regard to the optimal configuration. These authors [34] found an improvement in the performance of VAWT at lower speeds using cambered blades. All the different results present in the literature suggest the need to obtain more insight into the influence of airfoil camber on the performance of VAWTs.…”

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confidence: 99%

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Parametrical evaluation of the aerodynamic performance of vertical axis wind turbines for the proposal of optimized designs

Meana-Fernández

Solís-Gallego

Oro

et al. 2018

Energy

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Many studies have tried to give insight into the optimal values of solidity and the airfoil geometry that maximize the performance and self-starting capability of vertical axis wind turbines, but there is still no consensus. In addition, most studies focus on one particular airfoil or airfoil family, which makes the generalization of the results difficult. In this work, these research gaps are intended to be assessed. An exhaustive analysis of the influence of solidity, blade Reynolds number and airfoil geometry on the performance of a straight-bladed vertical axis wind turbine has been performed using a methodology based on streamtube models. An airfoil database of 34 airfoils has been generated, developing a practical and cost-effective tool for the quick comparison of turbine designs (70 different configurations were analyzed). This tool, validated with results from the literature and computational fluid dynamics simulations performed by the authors, has allowed to propose an optimal solidity range from 0.25 to 0.5 and the use of almost symmetrical airfoils (camber < 3%). Finally, this tool has been applied to design two vertical axis wind turbines optimized for low and medium wind speeds.

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Section: Influence Of Cambermentioning

confidence: 69%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Parametrical evaluation of the aerodynamic performance of vertical axis wind turbines for the proposal of optimized designs

Meana-Fernández

Solís-Gallego

Oro

et al. 2018

Energy

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“…The purpose of the authors was to investigate synthetic jet actuators on a water turbine. Darrieus wind turbine performance with cambered blades for different turbine solidity factor was analyzed by Qamar and Janajreh (2017). The authors analyzed torque and power of twodimensional turbine as a function of tip sped ratio for various number of blades and chord lengths utilized sliding mesh with k-ω turbulence model.…”

Section: Introductionmentioning

confidence: 99%

2-D CFD Computations of the Two-Bladed Darrieus-Type Wind Turbine

Rogowski

Hansen

Lichota

2018

JAFM

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In spite of the attractiveness of CFD methods and advanced measurement methods, there is still no full analysis of aerodynamic blade loads for vertical axis Darrieus-type wind turbines. Due to an inherently unsteady flow around the rotor blades, blade-wake-blade interaction and the occurrence of dynamic stall, the aerodynamics of this type of wind turbine is very complex. A two-bladed rotor have been investigated numerically for the tip speed ratio of 5.0. This paper compares results for aerodynamic blade loads obtained applying such turbulence models as: the standard k-ε; the RNG k-ε; the Realizable k-ε and the SST k-ω. As a result, quantitative instantaneous blade forces as well as instantaneous wake profiles behind the rotor have been obtained. Aerodynamic wake behind the rotor is also visualized by using streak lines. All CFD results are compared with experimental data taken from literature. Good agreement between the numerical results and the experiment is shown for the aerodynamic blade loads as well as for aerodynamic wake behind the rotor.

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“…Lei et al (2017) refined the grid close to the blades, generating three meshes and using the grid with the medium refinement because its results resembled more the experimental results. Qamar and Janajreh (2017) used three 2D VAWT meshes for the grid independence study and validated their simulations with experimental results. Tian, Mao, An, Zhang, and Wen (2017) used three meshes and validated experimentally the performance of a VAWT in the wake of moving vehicles.…”

Section: Introductionmentioning

confidence: 99%

Application of Richardson extrapolation method to the CFD simulation of vertical-axis wind turbines and analysis of the flow field

Meana-Fernández

Oro

Díaz

et al. 2019

Engineering Applications of Computational Fluid Mechanics

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There is still discrepancy regarding the verification of CFD U-RANS simulations of vertical-axis wind turbines (VAWTs). In this work, the applicability of the Richardson extrapolation method to assess mesh convergence is studied for several points in the power curve of a VAWT. A 2D domain of the rotor is simulated with three different meshes, monitoring the turbine power coefficient as the convergence parameter. This method proves to be a straightforward procedure to assess convergence of VAWT simulations. Guidelines regarding the required mesh and temporal discretization levels are provided. Once the simulations are validated, the flow field at three characteristic tip-speed ratio values (2.5-low, 4-nominal and 5-high) is analyzed, studying pressure, velocity, turbulent kinetic energy and vorticity fields. The results have revealed two main vortex shedding mechanisms, blade-and rotor-related. Vortex convection develops differently depending on the rotor zone (upwind, downwind, windward or leeward). Finally, insight into the loss of performance at off-design conditions is provided. Vortex shedding phenomena at the low tip-speed ratio explains the loss of performance of the turbine, whereas at the high tip-speed ratio, this performance loss may be ascribed to viscous effects and the rapid interaction between successive blade passings.

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A comprehensive analysis of solidity for cambered darrieus VAWTs

Cited by 40 publications

References 31 publications

Parametrical evaluation of the aerodynamic performance of vertical axis wind turbines for the proposal of optimized designs

Parametrical evaluation of the aerodynamic performance of vertical axis wind turbines for the proposal of optimized designs

2-D CFD Computations of the Two-Bladed Darrieus-Type Wind Turbine

Application of Richardson extrapolation method to the CFD simulation of vertical-axis wind turbines and analysis of the flow field

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