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RESEARCH PAPERS

# Measurement of Tip Vortex Paths in the Wake of a HAWT Under Yawed Flow Conditions

[+] Author and Article Information
Wouter Haans

Delft University of Technology, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS, Delft, The Netherlandsw.haans@lr.tudelft.nl

Tonio Sant

University of Malta, Faculty of Engineering, Tal-Qroqq, MSD 07, Msida, Malta

Gijs van Kuik, Gerard van Bussel

Delft University of Technology, Faculty of Aerospace Engineering, Kluyverweg 1, Delft, The Netherlands

J. Sol. Energy Eng 127(4), 456-463 (Jun 23, 2005) (8 pages) doi:10.1115/1.2037092 History: Received March 01, 2005; Revised June 23, 2005

## Abstract

Tip vortex locations have been measured in the wake of a model rotor in both axial flow and yaw using quantitative flow visualization. For each setting, the axial force coefficient has been derived, as well, from measurements. The results agree well with those previously published on the Delft University of Technology model rotor. The main interest is to determine the tip vortex pitch, wake skew angle, wake expansion, and to physically interpret the data. The results also help to validate and construct models. The tip vortex location data complement the existing skewed wake velocity data from hot-wire anemometry, making it a valuable experimental database.

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## Figures

Figure 1

Schematic top- and side-view of the experimental setup

Figure 2

Typical smoke-visualization photos, showing tip vortex cores and the blade. Note that flow is from left to right.

Figure 3

Diagram showing parallax correction

Figure 4

Definitions used in the wake geometry

Figure 5

Measured cT as function of λ and θtip for axial flow, on the DUT rotor

Figure 6

Measured tip vortex location for axial flow, on the DUT rotor. Vermeer: λ=7.85 for all θtip, present data: λ=7.92 for θtip=0deg, 4deg and λ=7.91 for θtip=2deg.

Figure 7

cT vs Ψ for all measured combinations of λ and θtip

Figure 8

Tip vortex location for λ=8, axial flow conditions. At the data points, the maximum random uncertainty intervals have been indicated with horizontal and vertical lines. Open symbols, dotted lines for θb=270deg, closed symbols, solid lines for θb=90deg.

Figure 9

U∕Ujet‐exit, measured locally in the empty tunnel section, at the location of the rotor plane, normalized with the maximum recorded value of U∕Ujet‐exit. (x,y)=(0,0) corresponds to the hub center, with the blades having a 0.6m radius.

Figure 10

Tip vortex location for λ=8, θtip=2deg and varying Ψ. Dashed and solid lines for downwind and upwind side, respectively.

Figure 11

Tip vortex location for Ψ=−30deg, λ=8 and varying θtip. Dashed and solid lines for downwind and upwind side, respectively.

Figure 12

Absolute value of skew wake angle χ vs ∣Ψ∣ for all measured combinations of λ and θ

Figure 13

∣χ∣ vs cT for three yawed conditions

Figure 14

Tip vortex pitch p∕R vs λ for measured combinations of Ψ and θtip. Dashed and solid lines for downwind and upwind side, respectively.

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