Vortex identification methods applied to wind turbine tip vortices

Soto‐Valle, Rodrigo; Cioni, Stefano; Bartholomay, Sirko; Μανωλέσος, Μαρίνος; Nayeri, Christian Navid; Bianchini, Alessandro; Paschereit, Christian Oliver

doi:10.5194/wes-7-585-2022

Cited by 14 publications

(5 citation statements)

References 36 publications

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“…Figure 9 also contains isosurfaces of the

Q

‐criterion, 53 which were used to reconstruct the tip vortices. The

Q

‐criterion is a common vortex identification method that is computed using the velocity gradient matrix

\nabla U

54 :

Q = \frac{1}{2} ((), tr {((), \nabla U)}^{2} - tr ((), {((), \nabla U)}^{2})),

where

tr

represents the mathematical trace of a matrix. The

Q

‐criterion identifies areas in the wake where the vorticity dominates the strain rate, revealing well‐defined tip vortices.…”

Section: Resultsmentioning

confidence: 99%

Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

van der Hoek,

den Abbeele,

Simao Ferreira

et al. 2024

Wind Energy

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Wind farm control can play a key role in reducing the negative impact of wakes on wind turbine power production. The helix approach is a recent innovation in the field of wind farm control, which employs individual blade pitch control to induce a helical velocity profile in a wind turbine wake. This forced meandering of the wake has turned out to be very effective for the recovery of the wake, increasing the power output of downstream turbines by a significant amount. This paper presents a wind tunnel study with two scaled wind turbine models of which the upstream turbine is operated with the helix approach. We used tomographic particle image velocimetry to study the dynamic behavior of the wake under the influence of the helix excitation. The measured flow fields confirm the wake recovery capabilities of the helix approach compared with normal operation. Additional emphasis is put on the effect of the helix approach on the breakdown of blade tip vortices, a process that plays an important role in re‐energizing the wake. Measurements indicate that the breakdown of tip vortices and the resulting destabilization of the wake are enhanced significantly with the helix approach. Finally, turbine measurements show that the helix approach was able to increase the combined power for this particular two‐turbine setup by as much as 15%.

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“…Figure 9 also contains isosurfaces of the

Q

‐criterion, 53 which were used to reconstruct the tip vortices. The

Q

‐criterion is a common vortex identification method that is computed using the velocity gradient matrix

\nabla U

54 :

Q = \frac{1}{2} ((), tr {((), \nabla U)}^{2} - tr ((), {((), \nabla U)}^{2})),

where

tr

represents the mathematical trace of a matrix. The

Q

‐criterion identifies areas in the wake where the vorticity dominates the strain rate, revealing well‐defined tip vortices.…”

Section: Resultsmentioning

confidence: 99%

Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

van der Hoek,

den Abbeele,

Simao Ferreira

et al. 2024

Wind Energy

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show abstract

“…The initial wake expansion downstream the 200 mm rotor was characterized in this study by the positions of the tip vortices shed by the turbine [6,28]. Phase-locked SPIV vorticity fields, computed from the averaging of 200 velocity maps, were used to track the tip vortex core locations (Fig.…”

Section: Near Wake Analysismentioning

confidence: 99%

Experimental investigation of the effects of the Reynolds number on the performance and near wake of a wind turbine

2023

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“…CC BY 4.0 License. Methods (VIM) from the literature (van der Wall and Richard, 2006;Soto-Valle et al, 2022) were adopted to outline the structure and decay of the tip vortex.…”

Section: Scope Of the Studymentioning

confidence: 99%

“…As summarized in Fig. 5, the tip vortex metrics were computed following the methodology commonly used in the literature (van der Wall and Richard, 2006;Soto-Valle et al, 2022): 220  vortex center C: the vortex center defines the axis of rotation of the vortical structure, and it is used to track the position of the tip vortex as it is convected downstream. In the present work, its position is computed from the resolved velocity field by calculating the λ2 scalar field (Jeong and Hussain, 1995), and locating the position of its minimum on the sampling plane.…”

Section: Tip Vortex Tracking Metricsmentioning

confidence: 99%

An insight into the capability of the Actuator Line Method to resolve tip vortices

Melani,

Mohamed,

Cioni

et al. 2023

Preprint

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Abstract. The Actuator Line Method (ALM) is being increasingly preferred to the ubiquitous Blade Element Momentum (BEM) approach in several applications related to wind turbine simulation, thanks to the higher level of fidelity required by the design and analysis of modern machines. This approach, however, still falls behind other medium-fidelity methodologies such as the Lifting Line Theory (LLT) when it comes to resolving the vortex-like structures shed at the blade tip (i.e., tip vortices) and their effect on the load profile along the blade. Despite the numerical strategies proposed so far to overcome this limitation, the reason for such behaviour is still unclear. Moving from this background, in this study the ALM’s capability to simulate tip effects is investigated. To this end, the ALM tool developed by the authors in the ANSYS® FLUENT® environment (v. 20.2) was employed for the simulation of a NACA0018 finite wing, for different pitch angles. Three different test cases were considered: high-fidelity blade-resolved CFD simulations, to be used as a benchmark, standard ALM, and ALM with the spanwise force distribution coming from blade-resolved data (frozen ALM). The last option was included to isolate the effect of force projection, using three different smearing functions. For the post-processing of the results, two different techniques were applied: the LineAverage sampling of the local angle of attack along the blade and state-of-the-art Vortex Identification Methods (VIM) to outline the blade vortex system. The analysis showed that the ALM can account for tip effects without the need of additional corrections, provided that the correct angle of attack sampling and force projection strategies are adopted.

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Vortex identification methods applied to wind turbine tip vortices

Cited by 14 publications

References 36 publications

Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

Experimental investigation of the effects of the Reynolds number on the performance and near wake of a wind turbine

An insight into the capability of the Actuator Line Method to resolve tip vortices

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