Detailed analysis of the blade root flow of a horizontal axis wind turbine

Herráez, Iván; Akay, B.; Bussel, G.J.W. Van; Peinke, Joachim; Stoevesandt, Bernhard

doi:10.5194/wes-1-89-2016

Cited by 33 publications

(26 citation statements)

References 32 publications

(59 reference statements)

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“…This explains the commonly observed stall delay of a rotating blade compared to equivalent two-dimensional conditions (e.g., Lindenburg, 2003;Snel et al, 1993). The current investigation supports the studies of Du and Selig (2000), Lindenburg (2003) and recently Herráez et al (2016), who explained radial flow with centrifugal force as well. In this study, the significantly higher blade solidity caused by the flat-back airfoils with large chord is seen to be responsible for a significant impact of three-dimensional effects.…”

Section: Three-dimensional Flow and Separation In The Root Regionsupporting

confidence: 92%

“…They could identify strong root vortices and high axial velocities in the root region. Recently, Herráez et al (2016) performed numerical simulations on the same rotor and characterized the Himmelskamp effect as well as the origins of span-wise flow. A similar study has been conducted by Bangga et al (2018) for the DTU 10 MW rotor.…”

Section: Flow Separation On Conventional Blade Root Geometries and Romentioning

confidence: 99%

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Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

et al. 2018

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Abstract. The present study investigates flow dynamics in the hub region of a wind turbine focusing on the influence of nacelle geometry on the root aerodynamics by means of Reynolds averaged Navier-Stokes simulations with the code FLOWer. The turbine considered is a generic version of the Enercon E44 converter incorporating blades with flat-back-profiled root sections. First, a comparison is drawn between an isolated rotor assumption and a setup including the baseline nacelle geometry in order to elaborate the basic flow features of the blade root. It was found that the nacelle reduces the trailed circulation of the root vortices and improves aerodynamic efficiency for the inner portion of the rotor; on the other hand, it induces a complex vortex system at the juncture to the blade that causes flow separation. The origin of these effects is analyzed in detail. In a second step, the effects of basic geometric parameters describing the nacelle have been analyzed with the purpose of increasing the aerodynamic efficiency in the root region. Therefore, three modification categories have been addressed: the first alters the nacelle diameter, the second varies the blade position relative to the nacelle and the third comprises modifications in the vicinity of the blade-nacelle junction. The impact of the geometrical modifications on the local flow physics are discussed and assessed with respect to aerodynamic performance in the blade root region. It was found that increasing the nacelle diameter deteriorates the root aerodynamics, since the flow separation becomes more pronounced. Possible solutions identified to reduce the flow separation are a shift of the blade in the direction of the rotation or the installation of a fairing fillet in the junction between the blade and the nacelle.

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Section: Three-dimensional Flow and Separation In The Root Regionsupporting

confidence: 92%

Section: Flow Separation On Conventional Blade Root Geometries and Romentioning

confidence: 99%

Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

et al. 2018

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“…This is to be expected although the reason is under discussion (Herráez et al, 2016) at the blade root area and has been attributed to span-wise pressure gradients (Schreck et al, 2010) and centrifugal forces on the boundary layer (Guntur and Sørensen, 2014). SFA values increase as λ decreases.…”

mentioning

confidence: 77%

Flow angle measurement of a yawed turbine and comparison to models

Gallant

Johnson

2017

Preprint

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Abstract. The torque generated by a wind turbine blade is dependent on several parameters, one of which is the angle of attack.Several models for predicting the angle of attack in yawed conditions have been proposed in the literature, but there is a lack of experimental data to use for direct validation.To address this problem, experiments were conducted under controlled conditions at the University of Waterloo Wind Generation Research Facility using a 3.4 m diameter test turbine. A five-hole pressure probe was installed in a modular 3D printed These five-hole probe measurements were also used to characterize the upstream flow profile. Wind speeds determined using the five-hole probe measurements are presented and are in agreement with measurements obtained in the wind facility during testing. The quality of results indicates the potential of the developed instrument for wind turbine measurements.

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“…In order to estimate if the observed flow patterns behind turbulators can also be found in rotating, three-dimensional blades, CFD simulations of a wind turbine rotor with generic defects are performed. The baseline model is a two-bladed wind turbine with clean blades that has been simulated and validated against experimental results in Herráez et al (2016). The turbine has a rotor diameter of 2 m and it employs the DU 96-W-180 airfoil along the whole blade span except at the cylindrical root connection to the hub.…”

Section: Wind Tunnel Measurements Of Turbulent Wedges On Airfoilsmentioning

confidence: 99%

“…A so-called arbitrary mesh interface connects the inner and outer parts of the domain, which consists of two independent block-structured meshes. This allows us to independently control the mesh resolution in both regions, which in turn makes if possible to reduce the number of cells in regions where a fine mesh is not required (see also Herráez et al, 2016).…”

Section: Wind Tunnel Measurements Of Turbulent Wedges On Airfoilsmentioning

confidence: 99%

Remote surface damage detection on rotor blades of operating wind turbines by means of infrared thermography

et al. 2018

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Abstract. Wind turbines are constantly exposed to wind gusts, dirt particles and precipitation. Depending on the site, surface defects on rotor blades emerge from the first day of operation on. While erosion increases quickly with time, even small surface defects can affect the performance of the wind turbine. Consequently, there is demand for an easily applicable remote monitoring method for rotor blades that is capable of detecting surface defects at an early stage. In this work it is investigated if infrared thermography (IRT) can meet these requirements by visualizing differences in the thermal transport and the corresponding surface temperature of the wall-bounded flow.Firstly, a validation of the IRT method compared to stereoscopic particle image velocimetry measurements is performed comparing both types of experimental results for the boundary layer of a flat plate. Then, the main characteristics of the flow in the wake of generic surface defects on different types of lifting surfaces are studied both experimentally and numerically: temperature gradients behind protruding surface defects on a flat plate and a DU 91-W2-250 profile are studied by means of IRT. The same is done with the wall shear stress from Reynolds-averaged Navier–Stokes simulations of a wind turbine blade. It is consistently observed, both in the experiments and the simulations, that turbulent wedges are formed on the flow downstream of generic surface defects. These wedges provide valuable information about the kind of defects that generate them. At last, experimental and numerical performance measures are taken into account for evaluating the aerodynamic impact of surface defects on rotor blades. We conclude that the IRT method is a suitable remote monitoring technique for detecting surface defects on wind turbines at an early stage.

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Detailed analysis of the blade root flow of a horizontal axis wind turbine

Cited by 33 publications

References 32 publications

Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

Flow angle measurement of a yawed turbine and comparison to models

Remote surface damage detection on rotor blades of operating wind turbines by means of infrared thermography

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