Experimental Investigation of Tip Vortex Meandering in the Near Wake of a
                        Horizontal-Axis Wind Turbine

Dahmouni, A. W.; Oueslati, Mohamed Mehdi; Nasrallah, Sassi Ben

doi:10.29252/jafm.73.245.27878

Cited by 6 publications

(4 citation statements)

References 18 publications

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“…In this section, the numerical results will be validated using the experimental results obtained in the CRTEn wind tunnel by Dahmouni et al (2017). They conducted an experimental study to analyze the meandering phenomenon of tip vortices in the near wake of a three-bladed HAWT model for different tip speed ratios λ= [3.50 -5.22].…”

Section: Validation Of the Obtained Resultsmentioning

confidence: 99%

“…The first one was the limit of mesh grid number related to the station computing capacities and the second reason was the meandering phenomenon of the tip vortices which is defined as an instantaneous fluctuation of the vortex core position (Devenport et al 1996;Roy et al 2011). In wind turbine case, as mentioned by (Bandyopadhyay et al 1991;Sherry et al 2013a,b andDahmouni et al 2017), the meandering phenomenon is due to the instantaneous changes in the vortex strength, the helical nature of the vortex tubes and the interaction between instabilities in the wake. However, no offset was observed for the first tip vortex because the meandering phenomenon increases as the vortices are far away from the rotor where the interactions between the tip vortices and the wake becomes more critical.…”

Section: Fig 5 Velocity Profiles At Different Positions Behind the Rmentioning

confidence: 99%

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Kelvin Waves Structure Analysis of a Horizontal Axis Wind Turbine Tip Vortices

Oueslati

Dahmouni

Nasrallah

2020

JAFM

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The optimization of the wind energy conversion is one of the most important domains which was widely interested researchers. The instabilities in the wind turbine wake are one of the sources of energy loss which strongly influenced the helical tube vortex structure and are generally difficult to be quantified using experimental facilities. This paper presents a numerical investigation on the wake downstream of a horizontal axis wind turbine (HAWT) model using the Fluent software. Results were validated using experimental measurements conducted in the CRTEn wind tunnel. The Kelvin wave's theory was, also, used to analyze the deformations acting on the tip vortices. The cartography of the velocity gradient tensor components of the first tip vortex and the different families of Kelvin wave's were studied and classified according to the azimuth wavenumber. The obtained results confirm that the tip vortices meandering correspond to the helical mode of Kelvin wave's and the stretching-compression phenomenon is the most important deformation acting on the tip vortex tubes during the development of HAWT wake.

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Section: Validation Of the Obtained Resultsmentioning

confidence: 99%

Section: Fig 5 Velocity Profiles At Different Positions Behind the Rmentioning

confidence: 99%

Kelvin Waves Structure Analysis of a Horizontal Axis Wind Turbine Tip Vortices

Oueslati

Dahmouni

Nasrallah

2020

JAFM

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“…Furthermore, Mula and Tinney (2014) and Dahmouni et al (2017) both indicated that kinetic energy is commonly adopted as a convergence criterion for the POD Snapshot method. The reduced-order POD model obtained can be utilized to reconstruct a velocity map with the majority of details that characterize flow behavior.…”

Section: Proper Orthogonal Decomposition Analysismentioning

confidence: 99%

Proper Orthogonal Decomposition Analysis of an Airfoil Performances under a Small Vortical Gust

Oueslati

Dahmouni

Salah

2023

JAFM

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This paper investigates the performance of a non-symmetric airfoil in a perturbed flow for a low Reynolds number by creating small vortical structures. A newly designed two-dimensional numerical tool is used to examine the interaction between the NACA 23015 airfoil and the vortex shedding from a square cylinder. Different airfoil position ratios are numerically simulated concerning the square cylinder G/D (D: square cylinder diameter), the channel centerline T/d (d=D/2), and the vortices scale size D/c (c: airfoil chord length). Results show that the maximum values of the lift and drag aerodynamic coefficients are influenced by the airfoil’s lateral and longitudinal positions. The Proper Orthogonal Decomposition (POD) method is used to identify the most energetic flow structures. For all simulated scenarios, it was found that the first two modes reflect the dominating coherent structures in the flow field. The results also show that a leading-edge vortex is formed over the airfoil. The observed phenomena of symmetric and antisymmetric shedding vortex mechanisms essentially depend on the lateral distance of the airfoil T/d and the vortex scale size D/c. However, the spectral analysis demonstrates that the shedding frequency mainly depends on the gap distance G/D.

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“…The results of large eddy simulation showed that the dimensionless mean velocity and Reynolds stress curves in the wake of HAWT show selfsimilarity through an appropriate choice of characteristic scales of velocity and length. In recent years, numerous efforts have been spent on the wake characteristics and the establishment of wake models for HAWTs (Noura et al 2016;Belkheir et al 2012;Dahmouni et al 2017;Kabir et al 2019;Qian et al 2022). However, the research on the wake characteristics of VAWT is not as extensive as that of HAWTs (Paraschivoiu 2002).…”

Section: Introductionmentioning

confidence: 99%

Self-similarity Characteristics of Vertical Axis Wind Turbine Wakes

2022

JAFM

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Wake generated by wind turbine can greatly influence the performance of downstream turbine. To better understand the wake self-similarity characteristics of vertical axis wind turbine (VAWT), the shear stress transport (SST) turbulence model with the addition of the γ-Reθ transition model is performed to model a twoblade VAWT at different operating conditions. The simulated blade surface pressure and torque are compared with existing experimental results for validation. Results show that, the simulated results after considering the transition model are more consistent with the experimental results. Analysis of the flow field shows that the average streamwise velocity of the wake in the horizontal plane under different tip speed ratios is asymmetry, but symmetric in the vertical plane. Further analysis indicates that, at different downstream positions, the nondimensional streamwise velocity deficit in the vertical plane remains self-similarity and basically coincides with the Gaussian distribution curve exclude the wake edges. In addition, the larger the tip speed ratio, the easier streamwise velocity deficit reach self-similarity state at downstream of the VAWT. The results of this study will be helpful to establish the wake model of the VAWT.

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Experimental Investigation of Tip Vortex Meandering in the Near Wake of a Horizontal-Axis Wind Turbine

Cited by 6 publications

References 18 publications

Kelvin Waves Structure Analysis of a Horizontal Axis Wind Turbine Tip Vortices

Kelvin Waves Structure Analysis of a Horizontal Axis Wind Turbine Tip Vortices

Proper Orthogonal Decomposition Analysis of an Airfoil Performances under a Small Vortical Gust

Self-similarity Characteristics of Vertical Axis Wind Turbine Wakes

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