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

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

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

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

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 177611

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

Free Wake model NREL test model FVE free wake model

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

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

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

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

Wake Analysis

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

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

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

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)

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

Load Analysis (Head-on Flow Case)

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

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

Comparison of predictions to NREL measurement data Normal Force Coefficient

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

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

Load Analysis (Yawed Flow Case)

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

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

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

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

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