Influence of the conservative rotor loads on the near wake of a wind turbine

Abstract. Presently there is a lack of data revealing the behaviour of the path followed by the near wake of full scale wind turbines and its dependence on yaw misalignment. Here we present an experimental analysis of the horizontal wake deviation of a 5 MW offshore wind turbine between 0.6 and 1.4 diameters downstream. The wake field has been scanned with a short range lidar and the wake path has been reconstructed by means of two-dimensional Gaussian tracking. We analysed the measurements for rotor yaw misalignments arising in normal operation and during partial load, representing high thrust coefficient conditions. We classified distinctive wake paths with reference to yaw misalignment, based on the nacelle wind vane, in steps of 3° in a range of ±10.5°. All paths observed in the nacelle frame of reference showed a consistent convergence towards 0.9 rotor diameters downstream suggesting a kind of wake deviation delay. This contrasts with published results from wind tunnels which in general report a convergence towards the rotor. The discrepancy is evidenced in particular in a comparison which we performed against published paths obtained by means of tip vortex tracking.

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An experimental study on the near wake characteristics of a wind turbine model subjected to surge, pitch, and heave motions

10.31274/etd-180810-3919 ◽

2015 ◽

Cited By ~ 1

Author(s):

Morteza Khosravi

Keyword(s):

Experimental Study ◽

Wind Turbine ◽

Near Wake ◽

Turbine Model ◽

Wake Characteristics

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Experimental Investigation on the Tip Vortex of a Wind Turbine With and Without a Slotted Tip

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2017-64125 ◽

2017 ◽

Author(s):

Pengyin Liu ◽

Jinge Chen ◽

Shen Xin ◽

Xiaocheng Zhu ◽

Zhaohui Du

Keyword(s):

Experimental Data ◽

Flow Field ◽

Wind Turbine ◽

Vortex Core ◽

Control Method ◽

Tip Vortex ◽

Wake Flow ◽

Core Model ◽

Near Wake ◽

Measured Velocity

In this paper, a slotted tip structure is experimentally analyzed. A wind turbine with three blades, of which the radius is 301.74mm, is investigated by the PIV method. Each wind turbine blade is formed with a slots system comprising four internal tube members embedded in the blade. The inlets of the internal tube member are located at the leading edge of the blade and form an inlet array. The outlets are located at the blade tip face and form an outlet array. The near wake flow field of the wind turbine with slotted tip and without slotted tip are both measured. Velocity field of near wake region and clear images of the tip vortex are captured under different wake ages. The experimental results show that the radius of the tip vortex core is enlarged by the slotted tip at any wake age compared with that of original wind turbine. Moreover, the diffusion process of the tip vortex is accelerated by the slotted tip which lead to the disappearance of the tip vortex occurs at smaller wake age. The strength of the tip vortex is also reduced indicating that the flow field in the near wake of wind turbine is improved. The experimental data are further analyzed with the vortex core model to reveal the flow mechanism of this kind of flow control method. The turbulence coefficient of the vortex core model for wind turbine is obtained from the experimental data of the wind turbine with and without slotted tip. It shows that the slotted tip increases the turbulence strength in the tip vortex core by importing airflow into the tip vortex core during its initial generation stage, which leads to the reduction of the tip vortex strength. Therefore, it is promising that the slotted tip can be used to weaken the vorticity and accelerate the diffusion of the tip vortex which would improve the problem caused by the tip vortex.

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A Measurement of the Three-Dimensional Near-Wake Velocity Field of a Model Horizontal-Axis Wind Turbine

Challenges of Power Engineering and Environment ◽

10.1007/978-3-540-76694-0_199 ◽

2007 ◽

pp. 1078-1083

Author(s):

Danmei Hu ◽

Jianxing Ren ◽

Zhaohui Du

Keyword(s):

Velocity Field ◽

Wind Turbine ◽

Three Dimensional ◽

Horizontal Axis ◽

Horizontal Axis Wind Turbine ◽

Near Wake

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The effect of dynamic near-wake modulation on utility-scale wind turbine wake development

Journal of Physics Conference Series ◽

10.1088/1742-6596/1618/6/062063 ◽

2020 ◽

Vol 1618 ◽

pp. 062063

Author(s):

Aliza Abraham ◽

Luis A Martínez-Tossas ◽

Jiarong Hong

Keyword(s):

Wind Turbine ◽

Near Wake ◽

Utility Scale ◽

Turbine Wake ◽

Wind Turbine Wake

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Near Wake Regime Study on Wind Turbine Blade Tip Vortex

Volume 2: Combustion, Fuels, and Emissions; Renewable Energy: Solar and Wind; Inlets and Exhausts; Emerging Technologies: Hybrid Electric Propulsion and Alternate Power Generation; GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2019-2493 ◽

2019 ◽

Author(s):

Ojing Siram ◽

Niranjan Sahoo

Keyword(s):

Wind Turbine ◽

Strouhal Number ◽

Vortex Shedding ◽

Flow Condition ◽

Pitch Angle ◽

Tip Vortex ◽

Near Wake ◽

Helical Vortex ◽

Blade Tip ◽

Blade Pitch Angle

Abstract In the present research article results on wind turbine blade tip vortex have been presented, the measurements have been done behind a model scale of horizontal axis wind turbine rotor. The rotor used for flow characterization is a three-bladed having NACA0012 cross-section, the study has been performed for low range tip speed ratio of 0–2 and wind speeds range of 3–6 m/s. The investigation has been conducted specifically to near wake regime, which is often expressed as the region of regular helical vortex structures. Although this nature of regular helical vortex pattern has always been a question of debate with respect to changes in the flow condition, rotor geometry and point of measurements. A systematic experiment was done mainly on the frequency of vortex shedding through hot-wire anemometry (HWA), and the corresponding frequency is express in terms of Strouhal number. Present article work within near wake regime includes tip vortex shedding stability analysis for different blade pitch angle and flow condition. From the systematic experimental observation, the evaluated data indicate that the Strouhal number has an incremental trend when the blade pitch angle is close to 40°, and above it inconsistency in frequency response is observed.

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