CFD Simulation: MEXICO Rotor Wake

CFD Simulation: MEXICO Rotor Wake

EWEC: 2009Andreas Bechmann & Niels Sørensen

Risø DTU ∙ National Laboratory for Sustainable [email protected]

Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark

Outline:

1. Background

2. MEXICO Experiment

3. CFD Simulations

4. Conclusion

17 March 09CFD Simulation of the MEXICO Rotor Wake2


Background 1/3

“Today, siting of wind turbines in wind farms is based on power output considerations”

TOPFARM project: Optimization of wind farm topology based on power output and turbine loads.

WP1: Internal flow modelModel to describe the flow inside the wind farm



Background 2/3

How to validate the model?


Wind tunnelSingle wind turbine

Wind farm


Background 3/3

Objectives:To make a “clean” dataset for validating wake models

Method:1.Extract wake data from the MEXICO experiment2.Compare measurements with high resolution CFD3.Combine measurements and CFD results in a dataset for validating wake models


Wind tunnel

The MEXICO Experiment• Controlled conditions• PIV measure. 1.3D downstream• Open wind tunnel – tunnel effects?


Outline:

1. Background


3. CFD Simulations

4. Conclusion

17 March 09Title of the presentation6


MEXICO Exp. 1/4 MEXICO Info:(pictures by ECN, NLR)

•Model Experiments in Controlled Conditions•Purpose: ”measurements on wind turbine model including the near wake”•Large tunnel of DNW used•Many groups participated: ECN was coordinator

The Vindtunnel:•Open section 9.5×9.5m•Max. air speed 30 m/s•Balance (3 forces/moments)



MEXICO Exp. 2/4

The Rotor:•4.5m diameter•3 airfoils for each blade:

1. Root: DU 91-W2-250

2. Mid: RISØ A1-213. Tip: NACA 63-418

•Zig-zag tape at 5% chord•Pitch angle -2.3 degrees•No signal from strain gages? (global rotor forces are estimated from the balance)•Pressure at 5 sections (25%,35%,60%,82%,95%)



MEXICO Exp. 3/4

The PIV measurements:• PIV measuring sheet (34×40cm) placed horizontally at 270 deg azimuth• In phase with rotor (freq=3 rotor revolutions) for 40s (100 samples) • Axial traverse at r/R=0.82• Radial traverses from r/R=0.5-0.9


1.3D-1.0D-0.6D -0.4D 0.3D 1.0D

1/10 scale of DNW wind tunnel

•Clear tunnel effects in the far wake•Tunnel effects limited at the rotor

Doeke RozendalFlow field measurements on a small scale wind turbine model in the DNW PLST wind tunnel NLR-CR-2003-485

Niels N. Sørensen, Risø/DTUMEXICO, 3. Progress Meeting, Athens 28-29Nov. 2001

Earlier CFD findings


MEXICO Exp. 4/4

Selected data:•100 GB of data•Axi-symmetric cond. No yaw•Pitch angle -2.3 degree•425 rpm (tip speed 100m/s)•Wind speed: 10, 15, 24 m/s (tip speed ratio 10, 6.7, 4.2)



Outline:

1. Background


3. CFD Simulations

4. Conclusion



The Simulations 1/5

CFD solver:•EllipSys3D•RANS: SST k-ω model•Fully turbulent•Steady-state simulations

Surface mesh:•All 3 blades meshed•256×64 cells on each

Volume mesh:•256 cells in normal direction (~7 rotor diameters)•Wake resolved approx 3D•Wind tunnel is not included



The Simulations 2/5

Rotor forces:Thrust. Estimated tower drag subtracted from balance forcePressure distributions.



The Simulations 3/5



The Simulations 4/5

Wake results:


1.3D-1.0D-0.6D -0.4D 0.3D 1.0D


The Simulations 5/5

Validation dataset :1.Tunnel effects removed2.Expands further downstream3.Airfoil characteristics has been extracted which includes 3D effects



Outline:

1. Background


3. CFD Simulations

4. Conclusions



• Wake data extracted from MEXICO database• CFD simulations of MEXICO wake were performed• Measurements and simulations compare well• Only the near-wake was simulated (~3D) (due to mesh topology)• Simulations with laminar–turbulent transition could be interesting• A new validation dataset for wake models without tunnel effects

Thank you for listening!


Conclusions

Documents

CFD Simulation: MEXICO Rotor Wake