Comparison of 3D transitional CFD simulations for rotating wind turbine wings with measurements

Schaffarczyk, A. P.; Boisard, Ronan; Boorsma, K.; Dose, B.; Lienard, Caroline; Lutz, Thorsten; Madsen, Helge Aagaard; Rahimi, H.; Reichstein, Torben; Schepers, Gerard; Sørensen, Niels N.; Stoevesandt, Bernhard; Weihing, Pascal

doi:10.1088/1742-6596/1037/2/022012

Cited by 11 publications

(4 citation statements)

References 6 publications

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“…An analysis of the experimental data showed that natural transition of the Tollmien-Schlichting (T-S) kind took place (Lobo et al, 2018). As a part of this project, the first comparisons between CFD (computational fluid dynamics) predictions using turbulence models including transition modeling and such an experiment was conducted by four groups, and a reasonable agreement with the transition location compared to the experimental data was found (Schaffarczyk et al, 2018). However, in the case of atmospheric inflow, different transition scenarios are expected.…”

Section: Introductionmentioning

confidence: 85%

On the laminar–turbulent transition mechanism on megawatt wind turbine blades operating in atmospheric flow

Lobo

Özçakmak²,

Madsen

et al. 2023

Wind Energ. Sci.

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Abstract. Among a few field experiments on wind turbines for analyzing laminar–turbulent boundary layer transition, the results obtained from the DAN-AERO and aerodynamic glove projects provide significant findings. The effect of inflow turbulence on boundary layer transition and the possible transition mechanisms on wind turbine blades are discussed and compared to CFD (computational fluid dynamics) simulations of increasing fidelity (Reynolds-averaged Navier–Stokes, RANS; unsteady Reynolds-averaged Navier–Stokes, URANS; and large-eddy simulations, LESs). From the experiments, it is found that the transition scenario changes even over a single revolution with bypass transition taking place under the influence of enhanced upstream turbulence, for example, such as that from wakes, while natural transition is observed in other instances under relatively low inflow turbulence conditions. This change from bypass to natural transition takes place at azimuthal angles directly outside the influence of the wake indicating a quick boundary layer recovery. The importance of a suitable choice of the amplification factor to be used within the eN method of transition detection is evident from both the RANS and URANS simulations. The URANS simulations which simultaneously check for natural and bypass transition match very well with the experiment. The LES predictions with anisotropic inflow turbulence show the shear-sheltering effect and a good agreement between the power spectral density plots from the experiment and simulation is found in case of bypass transition. A condition to easily distinguish the region of transition to turbulence based on the Reynolds shear stress is also observed. Overall, useful insights into the flow phenomena are obtained and a remarkably consistent set of conclusions can be drawn.

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Section: Introductionmentioning

confidence: 85%

On the laminar–turbulent transition mechanism on megawatt wind turbine blades operating in atmospheric flow

Lobo

Özçakmak²,

Madsen

et al. 2023

Wind Energ. Sci.

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show abstract

“…Furthermore, transition was also successfully detected in the experimental data (Lobo et al, 2018), where the growth of T-S disturbances was identified as the main mechanism for the transition process. Also as a part of the MexNext project, seven transitional CFD computations from four groups were carried out, and reasonable agreement between the transition location determined based on the experimental data and the simulations was found (Schaffarczyk et al, 2018). In Schaffarczyk et al (2017) measurements on a rotor blade were carried out in the free atmosphere to study the behavior of the 970 B.…”

Section: Introductionmentioning

confidence: 91%

Investigation into boundary layer transition using wall-resolved large-eddy simulations and modeled inflow turbulence

2022

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Abstract. The objective of the present paper is to investigate the transition scenario of the flow around a typical section of a wind turbine blade exposed to different levels of inflow turbulence. A rather low Reynolds number of Rec=105 is studied at a fixed angle of attack but under five different turbulence intensities (TIs) up to TI = 11.2 %. Using wall-resolved large-eddy simulations combined with an inflow procedure relying on synthetically generated turbulence and a source-term formulation for its injection within the computational domain, relevant flow features such as the separation bubble, inflectional instabilities and streaks can be investigated. The study shows that the transition scenario significantly changes with rising TI, where the influence of inflectional instabilities due to an adverse pressure gradient decreases, while the influence of streaks increases, resulting in a shift from the classical scenario of natural transition to bypass transition. The primary instability mechanism in the separation bubble is found to be inflectional, and its origin is traced back to the region upstream of the separation. Thus, the inviscid inflectional instability of the separated shear layer is an extension of the instability of the attached adverse pressure gradient boundary layer observed upstream. The boundary layer is evaluated to be receptive to external disturbances such that the initial energy within the boundary layer is proportional to the square of the turbulence intensity. Boundary layer streaks were found to influence the instantaneous separation location depending on their orientation. A varicose mode of instability is observed on the overlap of the leading edge of a high-speed streak with the trailing edge of a low-speed streak. The critical amplitude of this instability was analyzed to be about 32 % of the free-stream velocity.

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“…Also as a part of the MexNext project, seven transitional CFD computations from four groups were carried out and reasonable agreement between the transition location determined based on the experimental data and the simulations was found (Schaffarczyk et al, 2018). In Schaffarczyk et al (2017) measurements on a rotor blade were carried out in the free atmosphere to study the behavior of the boundary layer within a specific zone on the suction side at different operational states.…”

Section: Introductionmentioning

confidence: 96%

Investigation Into Boundary Layer Transition Using Wall-Resolved LES and Modeled Inflow Turbulence

Lobo

Schaffarczyk

Breuer

2021

Preprint

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Abstract. The objective of the present paper is to investigate the transition scenario of the flow around a typical section of a wind turbine blade exposed to different levels of inflow turbulence. As a first step towards this objective, a rather low Reynolds number of Rec = 105 is studied at a fixed angle of attack but under five different turbulence intensities (TI) up to TI = 11.2 %. Using wall-resolved large-eddy simulations combined with an inflow procedure relying on synthetically generated turbulence and a source-term formulation for its injection within the computational domain, relevant flow features such as the separation bubble, inflectional instabilities and streaks can be investigated. The study shows that the transition scenario significantly changes with rising TI, where the influence of inflectional instabilities due to an adverse pressure gradient decreases, while the influence of streaks increases resulting in a shift from the classical scenario of natural transition to bypass transition. The primary instability mechanism in the separation bubble is found to be inflectional and its origin is traced back to the region upstream of the separation. Thus, the inviscid inflectional instability of the separated shear layer is an extension of the instability of the attached adverse pressure gradient boundary layer observed upstream. The boundary layer is evaluated to be receptive to external disturbances such that the initial energy within the boundary layer is proportional to the square of the turbulence intensity. Boundary layer streaks were found to influence the instantaneous separation location depending on their orientation. A varicose mode of instability is observed on the overlap of the leading edge of a high-speed streak with the trailing edge of a low-speed streak. The critical amplitude of this instability was analyzed to be about 32 % of the free-stream velocity.

show abstract

Comparison of 3D transitional CFD simulations for rotating wind turbine wings with measurements

Cited by 11 publications

References 6 publications

On the laminar–turbulent transition mechanism on megawatt wind turbine blades operating in atmospheric flow

On the laminar–turbulent transition mechanism on megawatt wind turbine blades operating in atmospheric flow

Investigation into boundary layer transition using wall-resolved large-eddy simulations and modeled inflow turbulence

Investigation Into Boundary Layer Transition Using Wall-Resolved LES and Modeled Inflow Turbulence

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