1. Numerical and Experimental Analysis of Performance and Aerodynamic Loads on HAWT Blade
AeroAcoustics & Noise Control Laboratory, Seoul National University
Jiwoong Park, Hyungki Shin, Hogeon Kim, Soogab Lee

2. Introduction Numerical Method Experimental Method Results & Analysis
Contents
Introduction
Numerical Method
Experimental Method
Results & Analysis
Concluding Remarks

3. Introduction Analysis & Validation Wind Tunnel Test Free Wake Analysis
NREL TEST
Curved vortex
Analysis &
Validation
SNU TEST
FVE Wake Model

4. Numerical models Vortex wake model
‘engineering models’ based on vortex methods
solved velocity potential expressed by Laplace Eqn.
application of Biot-Savart law
Free wake model or prescribed wake model
currently proper model to solve aerodynamic loading
added 3-d adjustment at stall region

5. CVC (Constant Vorticity Contour) Wake Structure
Free Wake model
CVC (Constant Vorticity Contour) Wake Structure
Circulation
Vortex sheet trailing from the interval (ra,rb) is replaced by a single vortex filament of constant strength
Ref. NASA Contractor Report

6. Free Wake Model Schematic of FVE Finite Vortex Element Free wake model
before vortex filaments hit the tower
vortex filaments strike against the tower
separated into vortex ring and horse-shoe vortices

7. Free Wake model
NREL test model
FVE free wake model

8. Corrigan Stall delay model Du & Selig Stall delay model
based on a shape function and local solidity
derived through correlation with prop-rotor and helicopter test
based on the analysis of three-dimensional integral laminar boundary layer equations
Corrected Aerodynamic Coefficient
Delayed Stall Angle
Shape function

9. Flow Chart pre-processor Main-processor post-processor
input geometry & operating condition
Calculate axial & radial induction factor by BEMT to apply initial downwash
Calculate initial circulation distribution & wake geometry
Calculate effective angle of attack at each blade section
Apply stall delay model to 2d table
Calculate blade loading based on airfoil data
Calculate blade loading based on circulation strength
Apply 2d drag data to blade loading
Output result data
Effective AOA > 2D stall AOA
Convergence criterion satisfied?
Calculate velocity field
Calculate circulation distribution
Regenerate wake release point based on new circulation distribution
Loop all azimuth angle
move free wake & check wake-tower interaction NO
YES

10. NREL Wind Tunnel Test NASA AMES WIND TUNNEL Wind Turbine
Test section : 25m  36m
Wind Turbine
Stall regulated type
2 Blades type
Blade Radius : 5.03m
Measurement
Shaft Torque
Root Bending Moment
Blade Surface Pressure
Reynolds no.
700,000~3,300,000

11. SNU Wind Tunnel Test KAFA WIND TUNNEL Wind Turbine
Test section : 2.45m  3.5m
1.225 m
Wind Turbine
1:50 Scale model of 750kW WT
3 Blades type
Blade Radius : 0.53m
Measurement
Shaft Torque
Velocity fluctuation by Hot-wire
Reynolds no.
70,000~130,000

12. Wake Analysis

13. Butterworth 5th order filter
Wake Analysis
Tip Vortex Measurement by Hot Wire Probe
Tip vortex
movement
Ref. TU-Delft wind tunnel test
Butterworth 5th order filter
Average of 3 Revolution
Raw data
Filtered data

14. Tip Vortex Measurement by Hot Wire Probe
Wake Analysis
Tip Vortex Measurement by Hot Wire Probe
Measurement points
r/R
time V dV
r/R
x/R
Tip vortex Trajectory
Tip vortex location dV

15. Validation of FVE Free Wake model
Wake Analysis
Validation of FVE Free Wake model
SNU model
FVE Free wake vs measured trajectory
Measurement data of SNU model
FVE free wake geometry

16. Validation of FVE Free Wake model
Wake Analysis
Validation of FVE Free Wake model
Wind speed : 13m/s
13m/s, TSR=6.5
13m/s, TSR=6.0, Yaw 10 deg.
13m/s, TSR=6.0
Wake geometry( TSR = 6.5, 6.0 )
Yawed flow case(10deg)

17. Wake Analysis Tip Vortex Pitch Angle SNU model
FVE Free wake VS measured data
Wind speed = 13m/s
Wind speed = 15m/s

18. Load Analysis
(Head-on Flow Case)

19. Comparison of predictions to NREL measurement data
Wake Geometry and Normal force distribution of NREL BLADE
FVE Wake Model
13m/s, TSR=3.0
Circulation and Normal force distribution
Wake geometry

20. Comparison of predictions to NREL measurement data
Shaft Torque
FVE Free wake model
apply stall delay model
3000
2500
2000
1500
1000
Torque (Nm)
500 5 10 15 20 25
-500
-1000
wind speed (m/s)
NREL
free wake with 2d table
free wake with Corrigan stall delay model
free wake with Du & Selig stall delay model

21. Comparison of predictions to NREL measurement data
Normal Force Coefficient

22. Comparison of predictions to SNU measurement data
Wake Geometry & Cn distribution of SNU BLADE
Curved Vortex vs FVE Wake Model
14 m/s, TSR=5.5
Curved
vortex
FVE
Free Wake
Wake Geometry
Cn distributions

23. Comparison of predictions to SNU measurement data
Shaft Torque Comparison
Curved Vortex vs FVE Wake Model
14 m/s, TSR=5.5
Shaft Torque Distribution

24. Load Analysis
(Yawed Flow Case)

25. Comparison of predictions to NREL measurement data
Wake Geometry of NREL BLADE
Curved Vortex vs FVE Wake Model
15 m/s, TSR=2.6
Yaw angle : 30 degree
Curved vortex
FVE Free Wake

26. Comparison of predictions to NREL measurement data
Normal Force Coefficient distribution
15 m/s, TSR=2.6
Yaw angle : 30 degree
r/R = 0.47
r/R = 0.3
r/R = 0.63
r/R = 0.80

27. Comparison of predictions to SNU measurement data
Wake Geometry & Cn distribution of SNU BLADE
Curved Vortex vs FVE Wake Model
14 m/s, TSR=5.5
Yaw angle : 10 degree
Curved Vortex vs FVE Wake Model
14 m/s, TSR=5.5
Yaw angle : 30 degree
Curved vortex
FVE Free Wake
Curved vortex
FVE Free Wake

28. Comparison of predictions to SNU measurement data
Shaft Torque Comparison
SNU Model
Yawed Flow
TSR=5.5

29. Concluding Remarks Wake Analysis Load Analysis Future work
FVE free wake model is devised and validated
Wake shape shows good agreement with measured geometry
Load Analysis
Validated by NREL and SNU model
Importance of the Wake-Tower interaction
Effectiveness of FVE free wake model
Future work
Refine free-wake model
Dynamic stall delay model
Aero-elastic model
Noise prediction model