Comparison and validation of BEM and free wake unsteady panel model with the Mexico rotor experiment

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Wind Turbine Wakes Extended Abstracts for Euromech Colloquium 508 20-22 October 2009, Madrid

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Comparison and Validation of BEM and Free Wake Unsteady

Panel Model with the MEXICO Rotor Experiment

D. Micallef1, M. Kloosterman2, C. Ferreira3, T. Sant4, G. van Bussel5

1_{DUWIND, TUDelft, Faculty of Aerospace Engineering, The Netherlands and University of} Malta, Department of Mechanical Engineering, Malta.

2,3_{DUWIND, TUDelft, Faculty of Aerospace Engineering, The Netherlands.} 4_{University of Malta, Department of Mechanical Engineering, Malta.}

5_{Professor, DUWIND, TUDelft, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS,} Delft, The Netherlands

Corresponding author D. Micallef

dmic0001@um.edu.mt

Abstract

The Model Rotor Experiments under Controlled Conditions (Mexico) project aimed at creating database of wind turbine rotor aerodynamic measurements under controlled conditions, for validating and improving wind turbine rotor aerodynamic simulation methods. An extensive measurement program was carried out on a three bladed 4.5m diameter rotor model in the DNW wind tunnel (test cross section of 9.5 × 9.5m). The measurements consisted of pressure distribution along the chord at five spanwise locations and Stereo Particle Image Velocimetry at certain location of the flow field, including tip vortex. The measurements included both yawed and axial conditions.

In this work we present some of the results of the MEXICO experiment and use them for validation and comparison between blade element momentum codes and free wake unsteady potential flow codes. The comparison is performed with results for the non-yawed and yawed case, with special focus on the evaluation of the effect of yaw.

Load and power curves as well as spanwise load distributions in axial flow (such as fig. 1 and fig. 2) are presented comparing the results from experiment with a BEM model without 3D effect corrections. This helps in identifying the how much the use of 2D airfoil data affects the computations. These results are also shown for the case of yawed flow. 3D airfoil data was derived from experiment using the angles of attack found from the BEM model. This was also done for the yawed flow cases where hysteresis loops were observed highlighting the dynamic nature of the flow. A direct free wake code was also used for axial flow cases and tip vortex trajectories were compared with the PIV data (see fig. 3). The tip vortex strength decay in the near wake was also compared (see fig. 4) along with a comparison between the flow field close to the tip vortex and the rolled up vortex sheet from the free wake model.

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47 References

Model Experiments in Controlled Conditions(MEXICO) - Final Report

M.H.M. Kloosterman, \emph{Development of the Near Wake behind a Horizontal Axis Wind Turbine Including the development of a Free Wake Lifting Line Code} - M.Sc Dissertation, TUDelft.

Figure 1 -Example validation of BEM simulations with experimental data, thrust coefficient vs. tip speed ratio, non-yawed flow case.

Figure 2 - Example validation of BEM simulations with experimental data, power coefficient vs. tip speed ratio, non-yawed flow case.

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Figure 3 - Simulation with free wake model (blue) vs. experimental surface of the tip vortex (green).