Wind tunnel investigation on the effect of the turbine tower on wind turbines wake symmetry

Pierella, F.; Sætran, Lars Roar

doi:10.1002/we.2120

Cited by 19 publications

(21 citation statements)

References 26 publications

(35 reference statements)

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“…The interaction of the rotor wake with the turbine tower is identified to be the main contributor for the asymmetric wake flow. This finding is supported by a previous study on the non-yawed wake by Pierella and Saetran (2017), in which they attributed a significant displacement of the wake center to the interaction with the turbine tower.…”

Section: Test Case 1: Aligned Turbinessupporting

confidence: 83%

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

2018

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Abstract. In this experimental wind tunnel study the effects of intentional yaw misalignment on the power production and loads of a downstream turbine are investigated for full and partial wake overlap. Power, thrust force and yaw moment are measured on both the upstream and downstream turbine. The influence of inflow turbulence level and streamwise turbine separation distance are analyzed for full wake overlap. For partial wake overlap the concept of downstream turbine yawing for yaw moment mitigation is examined for different lateral offset positions.Results indicate that upstream turbine yaw misalignment is able to increase the combined power production of the two turbines for both partial and full wake overlap. For aligned turbine setups the combined power is increased between 3.5 % and 11 % depending on the inflow turbulence level and turbine separation distance. The increase in combined power is at the expense of increased yaw moments on both the upstream and downstream turbine. For partial wake overlap, yaw moments on the downstream turbine can be mitigated through upstream turbine yawing. Simultaneously, the combined power output of the turbine array is increased. A final test case demonstrates benefits for power and loads through downstream turbine yawing in partial wake overlap. Yaw moments can be decreased and the power increased by intentionally yawing the downstream turbine in the opposite direction.

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Section: Test Case 1: Aligned Turbinessupporting

confidence: 83%

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

2018

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“…In full-scale scenarios, the ground, wind shear and rotor tilt would further contribute to the effect. For potential floating turbines, a pitch motion will deflect the wake upwards; see Rockel et al (2014). This vertical deflection will interact with the vertical transport shown in Fig.…”

Section: Discussionmentioning

confidence: 98%

Wind tunnel experiments on wind turbine wakes in yaw: redefining the wake width

et al. 2018

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Abstract. This paper presents an investigation of wakes behind model wind turbines, including cases of yaw misalignment. Two different turbines were used and their wakes are compared, isolating effects of boundary conditions and turbine specifications. Laser Doppler anemometry was used to scan full planes of wakes normal to the main flow direction, six rotor diameters downstream of the respective turbine. The wakes of both turbines are compared in terms of the time-averaged main flow component, the turbulent kinetic energy and the distribution of velocity increments. The shape of the velocity increments' distributions is quantified by the shape parameter λ2. The results show that areas of strongly heavy-tailed distributed velocity increments surround the velocity deficits in all cases examined. Thus, a wake is significantly wider when two-point statistics are included as opposed to a description limited to one-point quantities. As non-Gaussian distributions of velocity increments affect loads of downstream rotors, our findings impact the application of active wake steering through yaw misalignment as well as wind farm layout optimizations and should therefore be considered in future wake studies, wind farm layout and farm control approaches. Further, the velocity deficits behind both turbines are deformed to a kidney-like curled shape during yaw misalignment, for which parameterization methods are introduced. Moreover, the lateral wake deflection during yaw misalignment is investigated.

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“…Also the wake behind the non-yawed turbine is seen to be slightly deflected in positive z-direction, which is assumed to stem from the interaction of the rotating wake with the turbine tower. As discussed by Pierella and Saetran (2017) who performed experiments on the same rotor with a larger tower, the tower-wakeinteraction can lead to an uneven momentum entrainment in the wake. Increasing the turbulence level from T I A =0.23% to T I B =10.00% is found to only have a small influence on the wake deflection.…”

Section: γ=-30mentioning

confidence: 99%

Wind tunnel experiments on wind turbine wakes in yaw: Effects of inflow turbulence and shear

Bartl¹,

Mühle²,

Schottler³

et al. 2018

Preprint

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Abstract. The wake characteristics behind a yawed model wind turbine exposed to different customized inflow conditions are investigated. Laser Doppler Anemometry is used to measure the wake flow in two planes at x/D=3 and x/D=6 while the turbine yaw angle is varied from γ = [−30• , 0The objective is to assess the influence of grid-generated inflow turbulence and shear on the mean and turbulent flow components.The wake flow is observed to be asymmetric with respect to negative and positive yaw angles. A counter-rotating vortex pair 5 is detected creating a kidney-shaped velocity deficit for all inflow conditions. Exposing the rotor to non-uniform shear inflow changes the mean and turbulent wake characteristics only insignificantly. At low inflow turbulence the curled wake shape and wake center deflection are more pronounced than at high inflow turbulence. For a yawed turbine the rotor-generated turbulence profiles peak in regions of strong mean velocity gradients, while the levels of peak turbulence decrease at approximately the same rate as the rotor thrust.

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Wind tunnel investigation on the effect of the turbine tower on wind turbines wake symmetry

Cited by 19 publications

References 26 publications

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

Wind tunnel experiments on wind turbine wakes in yaw: redefining the wake width

Wind tunnel experiments on wind turbine wakes in yaw: Effects of inflow turbulence and shear

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