MODEL TESTS OF TWISTED FLOW WIND-TUNNEL DESIGNS FOR TESTING YACHT SAILS

This paper presents the results obtained in the course of developing a special wind tunnel aimed at reproducing the variation in the onset w ind speed and direction with height up the mast as seen by yachts as t hey sail in the boundary layer above the sea. Earlier work has shown t hat the variation in the wind speed with height can easily be modelled using standard boundary layer wind tunnel techniques. The variation i n wind direction with height is a more difficult problem with which to deal. The paper shows results from a pilot wind tunnel study which in vestigated two concepts to produce sheared twisted flow. Both of these concepts were successful, but the concept using a series of twisted v anes gave the better solution as the area of good flow was larger than that produced by a dual wind tunnel concept, and, it is a more econom ical solution from the point of view of both running and initial capit al costs.