Wind-tunnel pressure measurements on model-scale rigid downwind sails

P. Bot, Ignazio Maria Viola, Richard G. J. Flay, Jean-Sebastien Brett

Research output: Contribution to journalSpecial issuepeer-review

Abstract

This paper describes an experiment that was carried out in the Twisted Flow Wind Tunnel at The University of Auckland to measure a detailed set of pressure distributions on a rigid 1/15th scale model of a modern asymmetric spinnaker. It was observed that the pressures varied considerably up the height of the spinnaker. The fine resolution of pressure taps allowed the extent of leading edge separation bubble, pressure recovery region, and effect of sail curvature to be observed quite clearly. It was found that the shape of the pressure distributions could be understood in terms of conventional aerodynamic theory. The sail performed best at an apparent wind angle of about 55°, which is its design angle, and the effect of heel was more pronounced near the head than the foot. Analysis of pressure time histories allows the large scale vortex shedding to be detected in the separation region, with a Strouhal number in the range 0.1–0.3, based on local sail chord length.
Original languageEnglish
Pages (from-to)84
Number of pages92
JournalOcean Engineering
Volume90
DOIs
Publication statusPublished - 1 Nov 2014

Keywords

  • Sails aerodynamics
  • Downwind sail
  • Pressure measurements
  • Leading-edge separation
  • Laminar separation bubble
  • Trailing-edge separation

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