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Experimental and Numerical Study of Radial Flow. D. Micallef, B. Akay, T. Sant, C. S. Ferreira, G. Van Bussel Presenter: Daniel Micallef Date: 17/03/2011. Presentation Overview. Introduction Previous work The SPIV experiment Numerical simulation Results Conclusions and contributions.
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Experimental and Numerical Study of Radial Flow D. Micallef, B. Akay, T. Sant, C. S. Ferreira, G. Van Bussel Presenter: Daniel Micallef Date: 17/03/2011
Presentation Overview • Introduction • Previous work • The SPIV experiment • Numerical simulation • Results • Conclusions and contributions
Introduction • The objectives of this work were the following: • Understand flow three-dimensionality of wind turbines • Understanding of the very near wake evolution • Investigate the relevance of radial flows to wind turbine designers • Study concerns flow outside of the boundary layer
Introduction • To this end, both an experimental and numerical study were performed: • Potential flow, 3D unsteady panel model • SPIV experiment
Previous Work • Ebert et al. – Hot-wire measurements. Radial velocities (at a position x/c = 1.67) λ = 4
Previous Work • Sant et al. – NREL UAE Phase VI experimental dataset used in a free-wake lifting line model λ = 7.6 λ = 2.91 λ = 1.52 a3,c r/R
SPIV Experiment • SPIV setup for measurements along the spanwise direction: Laser Turbine Cameras
SPIV Experiment Laser sheet Turbine Laser Cameras
SPIV Experiment • Experimental conditions: • Wind speed 6m/s • RPM 400 • Tip speed ratio of 7 • Thrust coefficient of 0.87 • Power coefficient 0.44
Numerical Simulation • Solves for the source and doublet distribution on panels representing the body and wake.
Numerical Simulation • Model used is: • Three-dimensional • Unsteady • Potential flow without any stall model • The experimental tip speed ratio was simulated (attached conditions)
Numerical Simulation • Verification tests (convergence tests shown here at 50% span):
Results • Radial velocity results on a horizontal plane.
Results • Video radial velocities behind the turbine
Results • Snapshot comparisons between simulation and experiment: 80 degrees
Results • 90 degrees
Results • 100 degrees
Results 97 deg 95 deg 99 deg
Results • Load comparison from panel model
Results • The force in the spanwise direction is small. • Radial velocities however also impact the thrust force due to the wake dynamics. • These effects still need to be clarified.
Conclusions and contributions • Experimental observations very close to the rotor plane were performed using SPIV • Spanwise loads were confirmed to be small compared to the other force components • A slight wake contraction just behind the rotor plane was observed experimentally. Numerical results also show a delayed expansion.
Conclusions and contributions • Future work plans: • Chordwise experimental measurements • Study of the yawed flow situation. Radial components are expected to be higher due to the flow asymmetry leading to more complex wake kinematics