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Research Papers

# Analysis of the Flow Characteristics of Two Nonrotating Rotor Blades

[+] Author and Article Information
R. P. van Rooij

Wind Energy Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlandsr.p.j.o.m.vanrooij@tudelft.nl

J. Sol. Energy Eng 130(3), 031015 (Jul 16, 2008) (13 pages) doi:10.1115/1.2931507 History: Received February 21, 2007; Revised September 17, 2007; Published July 16, 2008

## Abstract

The investigation focuses on the analysis of the airfoil segment performances along rotor blades in the parked configuration. In this research, wind tunnel experiments on two twisted blade geometries with different airfoils played a dominant role. These measurements were carried out by the Swedish Aeronautical Research Institute, former FFA, and by the American National Renewable Energy Laboratories (NREL) during the Unsteady Aerodynamic Experiment. The spans of the blades were $2.375m$ and $5m$, the STORK 5 WPX and the NREL Phase VI blade, respectively. Five span locations (inboard, midspan, outboard, and tip regions) were considered and compared with the 2D airfoil characteristics. Wing model experiments with similar blade aspect ratio were included in the research. Furthermore, the commercial computational fluid dynamics code FLUENT was used for the validation and analysis of the spanwise lift and drag coefficients at four different pitch settings, $20deg$, $30deg$, $45deg$, and $60deg$. The computed pressure distributions compared reasonably well, but the derived lift and drag showed quite some differences with the blade measurements. The lift coefficients for the sections beyond the leading-edge stall angle of the STORK blade were larger than for the NREL blade and were close to that of a wing model with similar airfoil and aspect ratio. Lift and drag coefficients for the sections of the two blades were always much smaller than the 2D results. The drag values for both blades showed quite some agreement, and airfoil and blade dependency seemed to be small.

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## Figures

Figure 2

The lift curves from the blade measurements compared to 2D experimental data of CSU

Figure 3

The drag curves from the blade sections compared to 2D experimental data of CSU

Figure 4

The lift characteristics from the twisted blade measurements compared to those of the straight wing model of Ostowari and Naik (1-2)

Figure 5

The drag curves from the twisted blade measurements compared to those of the straight wing model (1-2)

Figure 6

Grid description and domain composition

Figure 7

CFD (DES) pressure distributions for the NREL blade at a pitch angle of 20deg compared with the spanwise results from the experiment

Figure 8

Comparison of the spanwise pressure distributions for the NREL blade at a pitch angle of 60deg between CFD (DES) and experiment

Figure 9

Comparison of the spanwise pressure distributions for the FFA blade at a pitch angle of 20deg between CFD (DES) and experiment

Figure 10

Comparison of the spanwise pressure distributions for the FFA blade at a pitch angle of 26deg between CFD (k-ω) and experiment. Upper left corner is at r∕=0.30 and varies via r∕R=0.55, 0.75, 0.85, 0925 to r∕R=0.95 at the bottom right. Picture from Ref. 7.

Figure 1

Blade planform and pressure tap locations of the blade in the NREL tests and the STORK 5 WPX blade (12)

Figure 11

Comparison of the spanwise pressure distributions for the FFA blade at a pitch angle of 30deg between CFD (DES) and experiment

Figure 12

The lift characteristics of computed and measured FFA and NREL blade. The measured blade segment data are in the areas of FFA and NREL (horizontal lines).

Figure 13

The drag performance of the computed and measured FFA and NREL blade. The measured segment data are in the areas of FFA and NREL (horizontal lines).

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