3D URANS analysis of a vertical axis wind turbine in skewed flows

Orlandi, Alessio; Collu, Maurizio; Zanforlin, Stefania; Shires, Andrew

doi:10.1016/j.jweia.2015.09.010

Cited by 96 publications

(39 citation statements)

References 15 publications

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“…Their unsteady formulation and explicit wake modeling often lead to a better accuracy compared to streamtube models. More recently, CFD simulations have been widely used to predict the performance of VAWT's, such as 2D RANS simulations [15,16,17], 3D RANS simulations [18,19,20], and 2.5D Large-Eddy Simulations (LES) [21,22]. CFD has proven to be a useful tool to predict the turbine performance, instantaneous forces and the flow field around the turbine.…”

Section: Introductionmentioning

confidence: 99%

Comparison of low-order aerodynamic models and RANS CFD for full scale 3D vertical axis wind turbines

et al. 2017

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A Double Multiple Streamtube model, a free-wake vortex model (both widely used for vertical axis wind turbine design) and RANS CFD simulations are used in this work to predict the performance of the 17m Vertical Axis Wind Turbine, field tested by Sandia National Laboratories. The three-dimensional, full scale calculations are compared with the experiments in terms of power coefficient, power and instantaneous turbine torque to assess the validity of each model. Additionally, the two aerodynamic models and RANS CFD are compared to each other in terms of thrust and lateral force. The two models and CFD agree well with the experiments at the turbine optimal tip speed ratio. However, away from the optimal tip speed ratio, the streamtube model significantly deviates from the experimental data and from the other numerical models. RANS CFD gives a good agreement with the experiments, slightly underestimating the power coefficient at every tip speed ratio tested. The vortex model proves to be a useful tool with a better accuracy than the streamtube model and a much lower computational cost compared to RANS CFD.

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Section: Introductionmentioning

confidence: 99%

Comparison of low-order aerodynamic models and RANS CFD for full scale 3D vertical axis wind turbines

et al. 2017

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“…With the aim of constructing a high-fidelity simulation tool for VAWTs, the formulation of a 3D CFD model causing technically-acceptable computational costs still remains a relevant challenge.To the authors' best knowledge, only few 3D studies have been published on VAWT simulations. 3D URANS results of VAWT in skewed flows are presented in [11], 2D and 3D models are applied in [3] for aerodynamic modeling, and in [12] to investigate the self-starting capability of VAWT. The most advanced attempt of a fully 3D simulation of a VAWT is reported in [13], where a single-blade configuration was considered due to restrictions in computational cost.The present paper shows how a proper computational set-up allows obtaining reliable three-dimensional prediction of the flow around the rotor, of the wake, and of the turbine performance, at a reasonable (namely, industrially affordable) computational cost.…”

mentioning

confidence: 99%

“…To the authors' best knowledge, only few 3D studies have been published on VAWT simulations. 3D URANS results of VAWT in skewed flows are presented in [11], 2D and 3D models are applied in [3] for aerodynamic modeling, and in [12] to investigate the self-starting capability of VAWT. The most advanced attempt of a fully 3D simulation of a VAWT is reported in [13], where a single-blade configuration was considered due to restrictions in computational cost.…”

mentioning

confidence: 99%

Three-Dimensional CFD Simulation and Experimental Assessment of the Performance of a H-Shape Vertical-Axis Wind Turbine at Design and Off-Design Conditions

Franchina

Kouaissah

Persico

et al. 2019

IJTPP

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The paper presents the results of a computational study on the aerodynamics and the performance of a small-scale Vertical-Axis Wind Turbine (VAWT) for distributed micro-generation. The complexity of VAWT aerodynamics, which are inherently unsteady and three-dimensional, makes high-fidelity flow models extremely demanding in terms of computational cost, limiting the analysis to mainly 2D or 2.5D Computational Fluid-Dynamics (CFD) approaches. This paper discusses how a proper setting of the computational model opens the way for carrying out fully 3D unsteady CFD simulations of a VAWT. Key aspects of the flow model and of the numerical solution are discussed, in view of limiting the computational cost while maintaining the reliability of the predictions. A set of operating conditions is considered, in terms of tip-speed-ratio (TSR), covering both peak efficiency condition as well as off-design operation. The fidelity of the numerical predictions is assessed via a systematic comparison with the experimental benchmark data available for this turbine, consisting of both performance and wake measurements carried out in the large-scale wind tunnel of the Politecnico di Milano. The analysis of the flow field on the equatorial plane allows highlighting its time-dependent evolution, with the aim of identifying both the periodic flow structures and the onset of dynamic stall. The full three-dimensional character of the computations allows investigating the aerodynamics of the struts and the evolution of the trailing vorticity at the tip of the blades, eventually resulting in periodic large-scale vortices. technology dominates the market today but, in the aforementioned non-conventional environments, the Vertical-Axis Wind Turbine (VAWT) can be an interesting alternative, for several reasons: it is inherently 'aerodynamically' robust to yawed and skewed flows; it can provide a proper structural coupling with floating foundations (as demonstrated in the frame of the DeepWind EU program, [1]); it is characterized by lower costs of installation and maintenance as the gearbox and the generator can be placed on the ground; it produces lower acoustic pollution due to the lower optimal tip speed ratio with respect to HAWT. However, VAWT rotors are characterized by very complex aerodynamics, inherently unsteady, and fully three-dimensional, resulting in periodic fluctuating forces which ultimately complicate the structural design and affect the turbine performance.Several engineering methods were specifically developed for VAWTs, such as the multiple stream-tube and the double multiple stream-tube, that are analyzed in detail in [2]. In recent years, higher fidelity methods based on Computational Fluid Dynamics (CFD) have been applied to VAWTs, obtaining physically-sound representations of the flow field around the rotor [3-7], as well as quantitatively reliable performance estimates [8]. However, such simulations cause very high computational cost that has historically led the researchers to employ simplified actuator-line [9] or 2D...

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“…Distributions in Friction ForceThe distributions in the x-direction wall shear stress on each arm and blade in the respective Distribution of the x 1 -direction pressure-based force coefficients on each half-blade. The data at the respective span position were averaged over the seventh rotor-revolution using Equation(9).The pressure-based force coefficients (C px1_ave ) obtained by averaging the values of C m px1_ave along the half-blade span direction by Equation(10) are shown in…”

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confidence: 99%

Numerical Analysis of Effects of Arms with Different Cross-Sections on Straight-Bladed Vertical Axis Wind Turbine

et al. 2019

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Most vertical axis wind turbines (VAWTs) need arms connecting the blades with the rotational axis. The arms increase the power loss of VAWTs; however, the distribution between the pressure and friction influences and their degrees of influence have not yet been investigated in detail in past research. We applied computational fluid dynamics (CFD) targeting a small-sized straight-bladed VAWT to elucidate the effects of arms on turbine performance. In the analysis, three kinds of arms with different cross-sections (NACA 0018 airfoil, 18% rectangular, circular) with the same height were added to an armless rotor. The tangential forces and resistance torques caused by the added arms were recalculated by dividing the pressure and friction influences based on the surface pressure and friction distributions obtained by the CFD on an arm or a blade. The pressure-based tangential force of an arm, regardless of the cross-section, had a tendency to increase near the connection part between the arm and a blade. Though the value was small, the friction on the rectangular arm generated a driving force, whereas the friction on the other arms generated resistance forces. The pressure-based tangential force of a blade increased for a wide region around the connection part. The friction-based tangential force of a blade dropped around the connection part of every arm-equipped rotor. The arm resistance torque added to a VAWT by the existence of arms was larger than the added blade resistance torque in the cases of rectangular and circular arm rotors. Conversely, in the case of the airfoil arm rotor, the resistance torque added to blades became larger than that of arms.

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3D URANS analysis of a vertical axis wind turbine in skewed flows

Cited by 96 publications

References 15 publications

Comparison of low-order aerodynamic models and RANS CFD for full scale 3D vertical axis wind turbines

Comparison of low-order aerodynamic models and RANS CFD for full scale 3D vertical axis wind turbines

Three-Dimensional CFD Simulation and Experimental Assessment of the Performance of a H-Shape Vertical-Axis Wind Turbine at Design and Off-Design Conditions

Numerical Analysis of Effects of Arms with Different Cross-Sections on Straight-Bladed Vertical Axis Wind Turbine

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