Vortex Flow of Downwind Sails

Abel Arredondo-Galeana, Holger Babinsky, Ignazio Maria Viola

Research output: Contribution to journalArticlepeer-review


This paper sets out to investigate the vortex flow of spinnaker yacht sails, which are low-aspect-ratio highly-cambered wings used to sail downwind. We tested three model-scale sails with the same sections but different twists over a range of angles of attack in a water tunnel at a Reynolds number of 21 000. We measured the forces with a balance and the velocity field with particle image velocimetry. The sails experience massively separated three-dimensional flow and leading-edge vortices convect at half of the free stream velocity in a turbulent shear layer. Despite the massive flow separation, the twist of the sail does not change the lift curve slope, in agreement with strip theory. As the angle of attack and the twist vary, flow reattachment might occur in the time-average sense, but this does not necessarily result in a higher lift to drag ratio as the vorticity field is marginally affected. Finally, we investigated the effect of secondary vorticity, vortex stretching and diffusion on the vorticity fluxes. Overall, these results provide new insights on the vortex flow and associated force generation mechanism of wings with massively separated flow.
Original languageEnglish
Article numberE8
Early online date22 Feb 2023
Publication statusE-pub ahead of print - 22 Feb 2023


  • Separated flows
  • Vortex flows
  • Wing aerodynamics
  • Yacht sail


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  • Vortex flow of yacht sails

    Viola, I. M., Arredondo-Galeana, A. & Souppez, J.


    Project: Other (Non-Funded/Miscellaneous)

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