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Research Papers

Wind Tunnel Hotwire Measurements, Flow Visualization and Thrust Measurement of a VAWT in Skew

[+] Author and Article Information
Carlos J. Simão Ferreira

DUWIND —  Delft University Wind Energy Research Institute, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS, Delft, The NetherlandsC.J.SimaoFerreira@tudelft.nl

Gerard J. W. van Bussel

DUWIND —  Delft University Wind Energy Research Institute, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS, Delft, The NetherlandsG.J.W.vanBussel@tudelft.nl

Gijs A. M. van Kuik

DUWIND —  Delft University Wind Energy Research Institute, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS, Delft, The NetherlandsG.A.M.vanKuik@tudelft.nl

J. Sol. Energy Eng 128(4), 487-497 (Aug 01, 2006) (11 pages) doi:10.1115/1.2349550 History: Received February 06, 2006; Revised August 01, 2006

The results of experimental research on the wake and induced flow around a vertical axis wind turbine (VAWT) in skew are presented. The previous research on VAWTs in skew is limited because this operation mode has only recently been found to be significant in the operation of VAWTs in the built environment. These results contain hotwire measurements of the incoming flow and wake of a VAWT in nonskewed and skewed flow. The high sampling rate of the hotwire data allows the effects of blade passing to be identified. Flow visualization of the tip vortices is also presented. Thrust measurements of the rotor were performed to understand the effect of skew on thrust variation and to compare with analytical predictions.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 9

Curvature of the path of the tip vortex generated at the downstream blade position for the −30deg skew case (as described in Fig. 7)

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Figure 12

Flow U velocity component distribution at plane x=−47.5cm for six blade positions (Ux component). Nonskewed case, measurement plane as described in Fig. 1 (downwind view).

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Figure 13

Schematic of the measurement plane most downwind position +30deg skewed case

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Figure 14

Flow U velocity component (component in x direction) distribution at plane x′=−47.5cm (10cm upwind from blade, along x′) for six blade positions (Ux component), 30deg skewed flow case. Measurement plane as described in Fig. 1 (downwind view).

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Figure 15

Flow U velocity component distribution at plane x=0cm for six blade positions, nonskewed flow case. Measurement plane as described in Fig. 1 (downwind view).

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Figure 16

Schematic of measurement planes of measurements presented inside the rotor volume (Fig. 1) and of comparison across the rotor (Fig. 2)

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Figure 17

Comparison between a fixed wake geometry and real geometry of the wake at z=24cm, x=0cm

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Figure 18

Flow U velocity component distribution at plane x=42.5cm for six blade positions (Ux component). Nonskewed case, measurement plane as described in Fig. 1 (downwind view).

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Figure 19

Schematic of the downwind measurement plane in the nonskewed flow case

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Figure 20

Flow U velocity component distribution at plane x′=42.5cm, 30deg skew, for six blade positions. Measurement plane as described in Fig. 2 (downwind view).

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Figure 21

Schematic measurement plane downwind in 30deg skew

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Figure 22

Flow U velocity component distribution at plane x′=42.5cm, −30deg skewed flow, for six blade positions. Measurement plane as described in Fig. 2 (downwind view).

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Figure 23

Schematic measurement plane downwind of the rotor in −30deg skewed flow

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Figure 24

Flow U velocity component distribution at plane x=42.5cm, −15deg skew, for six blade positions. Measurement plane as described in Fig. 2 (downwind view).

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Figure 25

Schematic measurement plane downwind of the rotor in −15deg skew

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Figure 26

Comparison of the velocity profiles in the measurement planes downwind of the rotor for the 0, 15, and 30deg cases at the 90deg rotation instant

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Figure 27

Flow U velocity component distribution at plane x=−47.5cm, x=0cm, and x=42.5cm for two blade positions. Measurement plane as described in Fig. 1 (downwind view).

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Figure 8

Tip vortex of the downwind blade passage (generated at the 90deg position), in −30deg skewed flow, composed image. Photo plane as described in Fig. 7.

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Figure 7

Schematic photo plane for skewed flow tip vortex of Figs.  689 (figures show the side view)

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Figure 6

Tip vortex of the downwind blade passage (generated at the 90deg position), in −30deg skewed flow, at four moments of the rotation. Photo plane as described in Fig. 7.

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Figure 5

Schematic of the photo plane of Fig. 4 (photo from top view)

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Figure 4

Tip vortex of the upwind blade passage (generated at the 90deg position), nonskewed flow, at four moments of the rotation. Photo plane as described in Fig. 5, the grid unit corresponds to 1∕8 of a rotor diameter (D).

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Figure 3

Schematic of the photo plan of Fig. 2 (photo from side view)

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Figure 2

Tip vortex of the upwind blade passage (generated at the 90deg position), in nonskewed flow, at eight moments of the rotation. Photo plane as described in Fig. 3, the grid unit corresponds to 1∕8 of a rotor diameter (D).

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Figure 1

Schematic of the layout of the rotor of the H-Darrieus (two views)

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Figure 10

Average and confidence interval (95% confidence level) of a hotwire measurement (normalized by average of measurement) for three locations at the axis of rotation (x=0cm,y=0cm)

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Figure 11

Schematic of the upwind measurement plane

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Figure 28

Comparison of the variation, as a function of skew angle, of experimental thrust (this work), torque (experimental result of Mertens (2)) and theoretical prediction (Ferreira (4))

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