Horizontal axis wind turbine testing at high Reynolds numbers

Mark A. Miller, Janik Kiefer, Carsten Westergaard, Martin Otto Laver Hansen, Marcus Hultmark

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Detailed studies of modern large-scale wind turbines represent a significant challenge. The immense length scales characteristic of these machines, in combination with rotational effects, render numerical simulations and conventional wind tunnel tests unfeasible. Field experiments can give us important insight into the aerodynamics and operation, but they are always accompanied by large amounts of uncertainty, due to the changing nature of the inflow and the lack of accurate control of the test conditions. Here, a series of experiments is presented, using an alternative method that enables us to represent and study much of the physics governing the large-scale wind turbines in small-scale models. A specialized, compressed-air wind tunnel is used to achieve dynamic similarity with the field-scale, but under accurately controlled conditions of the laboratory. Power and thrust coefficients are investigated as a function of the Reynolds number up to ReD=14×106, at tip speed ratios representative of those typical in the field. A strong Reynolds number dependence is observed in the power coefficient, even at very high Reynolds numbers (well exceeding those occurring in most laboratory studies). We show that for an untripped rotor, the performance reaches a Reynolds number invariant state at Rec≥3.5×106, regardless of the tip speed ratio. The same model was also tested with scaled tripping devices, with a height of only 9μm, to study the effect of transition on the rotor performance. In the tripped case, the Reynolds number dependence was eliminated for all tested cases, suggesting that the state of the boundary layer is critical for correct predictions of rotor performance.
Original languageEnglish
Article number110504
JournalPhysical Review Fluids
Volume4
Issue number11
Number of pages22
ISSN2469-9918
DOIs
Publication statusPublished - 2019

Cite this

Miller, Mark A. ; Kiefer, Janik ; Westergaard, Carsten ; Hansen, Martin Otto Laver ; Hultmark, Marcus. / Horizontal axis wind turbine testing at high Reynolds numbers. In: Physical Review Fluids. 2019 ; Vol. 4, No. 11.
@article{10f3defcc313421fa8e2cf3a86492728,
title = "Horizontal axis wind turbine testing at high Reynolds numbers",
abstract = "Detailed studies of modern large-scale wind turbines represent a significant challenge. The immense length scales characteristic of these machines, in combination with rotational effects, render numerical simulations and conventional wind tunnel tests unfeasible. Field experiments can give us important insight into the aerodynamics and operation, but they are always accompanied by large amounts of uncertainty, due to the changing nature of the inflow and the lack of accurate control of the test conditions. Here, a series of experiments is presented, using an alternative method that enables us to represent and study much of the physics governing the large-scale wind turbines in small-scale models. A specialized, compressed-air wind tunnel is used to achieve dynamic similarity with the field-scale, but under accurately controlled conditions of the laboratory. Power and thrust coefficients are investigated as a function of the Reynolds number up to ReD=14×106, at tip speed ratios representative of those typical in the field. A strong Reynolds number dependence is observed in the power coefficient, even at very high Reynolds numbers (well exceeding those occurring in most laboratory studies). We show that for an untripped rotor, the performance reaches a Reynolds number invariant state at Rec≥3.5×106, regardless of the tip speed ratio. The same model was also tested with scaled tripping devices, with a height of only 9μm, to study the effect of transition on the rotor performance. In the tripped case, the Reynolds number dependence was eliminated for all tested cases, suggesting that the state of the boundary layer is critical for correct predictions of rotor performance.",
author = "Miller, {Mark A.} and Janik Kiefer and Carsten Westergaard and Hansen, {Martin Otto Laver} and Marcus Hultmark",
year = "2019",
doi = "10.1103/physrevfluids.4.110504",
language = "English",
volume = "4",
journal = "Physical Review Fluids",
issn = "2469-9918",
publisher = "American Physical Society",
number = "11",

}

Horizontal axis wind turbine testing at high Reynolds numbers. / Miller, Mark A.; Kiefer, Janik; Westergaard, Carsten; Hansen, Martin Otto Laver; Hultmark, Marcus.

In: Physical Review Fluids, Vol. 4, No. 11, 110504, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Horizontal axis wind turbine testing at high Reynolds numbers

AU - Miller, Mark A.

AU - Kiefer, Janik

AU - Westergaard, Carsten

AU - Hansen, Martin Otto Laver

AU - Hultmark, Marcus

PY - 2019

Y1 - 2019

N2 - Detailed studies of modern large-scale wind turbines represent a significant challenge. The immense length scales characteristic of these machines, in combination with rotational effects, render numerical simulations and conventional wind tunnel tests unfeasible. Field experiments can give us important insight into the aerodynamics and operation, but they are always accompanied by large amounts of uncertainty, due to the changing nature of the inflow and the lack of accurate control of the test conditions. Here, a series of experiments is presented, using an alternative method that enables us to represent and study much of the physics governing the large-scale wind turbines in small-scale models. A specialized, compressed-air wind tunnel is used to achieve dynamic similarity with the field-scale, but under accurately controlled conditions of the laboratory. Power and thrust coefficients are investigated as a function of the Reynolds number up to ReD=14×106, at tip speed ratios representative of those typical in the field. A strong Reynolds number dependence is observed in the power coefficient, even at very high Reynolds numbers (well exceeding those occurring in most laboratory studies). We show that for an untripped rotor, the performance reaches a Reynolds number invariant state at Rec≥3.5×106, regardless of the tip speed ratio. The same model was also tested with scaled tripping devices, with a height of only 9μm, to study the effect of transition on the rotor performance. In the tripped case, the Reynolds number dependence was eliminated for all tested cases, suggesting that the state of the boundary layer is critical for correct predictions of rotor performance.

AB - Detailed studies of modern large-scale wind turbines represent a significant challenge. The immense length scales characteristic of these machines, in combination with rotational effects, render numerical simulations and conventional wind tunnel tests unfeasible. Field experiments can give us important insight into the aerodynamics and operation, but they are always accompanied by large amounts of uncertainty, due to the changing nature of the inflow and the lack of accurate control of the test conditions. Here, a series of experiments is presented, using an alternative method that enables us to represent and study much of the physics governing the large-scale wind turbines in small-scale models. A specialized, compressed-air wind tunnel is used to achieve dynamic similarity with the field-scale, but under accurately controlled conditions of the laboratory. Power and thrust coefficients are investigated as a function of the Reynolds number up to ReD=14×106, at tip speed ratios representative of those typical in the field. A strong Reynolds number dependence is observed in the power coefficient, even at very high Reynolds numbers (well exceeding those occurring in most laboratory studies). We show that for an untripped rotor, the performance reaches a Reynolds number invariant state at Rec≥3.5×106, regardless of the tip speed ratio. The same model was also tested with scaled tripping devices, with a height of only 9μm, to study the effect of transition on the rotor performance. In the tripped case, the Reynolds number dependence was eliminated for all tested cases, suggesting that the state of the boundary layer is critical for correct predictions of rotor performance.

U2 - 10.1103/physrevfluids.4.110504

DO - 10.1103/physrevfluids.4.110504

M3 - Journal article

VL - 4

JO - Physical Review Fluids

JF - Physical Review Fluids

SN - 2469-9918

IS - 11

M1 - 110504

ER -