Abstract
Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the power and thrust coefficients of 8.2% and 15.0% for the wingletted case. A simple theoretical treatment of a two-turbine system suggests a possible positive tradeoff between increasing power and thrust coefficients at a wind farm scale. The higher thrust coefficient created a region of enhanced mean shear and turbulence in the outer portion of the wake. The winglets did not significantly change the tip-vortex strength, but higher levels of turbulence in the far wake decreased the tip-vortex strength. Because of the increased mean shear in the wingletted turbine’s wake, the Reynolds stresses were higher, potentially leading to a higher energy flux downstream.
Highlights
By restricting the spanwise velocity over a wing or turbine blade, the downwash created by wingtip vortices can be diminished, decreasing the induced drag [1] and leading to more favorable aerodynamics.The tip-vortex system induces velocities perpendicular to the freestream direction
This paper focuses on the study of wind turbine wakes behind turbines with and without winglets experiencing an incoming turbulent boundary layer in a laboratory wind tunnel
A simple method of estimating thrust coefficient is given in Equations (1) and (2), where T is the total thrust force, Uw is the velocity in the wake of the turbine, U∞ is the boundary layer velocity, and A is a plane of integration that captures the entirety of the wake deficit
Summary
By restricting the spanwise velocity over a wing or turbine blade, the downwash created by wingtip vortices can be diminished, decreasing the induced drag [1] and leading to more favorable aerodynamics.The tip-vortex system induces velocities perpendicular to the freestream direction. Imamura et al [5] investigated the effects of winglets on a wind turbine rotor with a vortex lattice method, and altered the dihedral angle (defined as the upward angle that the winglet makes from horizontal) from 80◦ to a 0◦ (equivalent to a radial extension). Their results suggested that a winglet positioned close to 90◦ from the plane of the rotor was most effective at increasing power coefficient, and showed that the decrease in downwash is highest for these winglets. The theory demonstrated that the Lanchester–Betz–Joukowsky limit holds for a turbine with winglets, and suggests that power increases come from a reduction in tip losses, rather than a downwind shift in wake vorticity as previously suggested by Van Bussel [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
