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 wind speed and direction with height up the mast as seen by yachts as they sail in the boundary layer above the sea. Earlier work has shown that the variation in the wind speed with height can easily be modelled using standard boundary layer wind tunnel techniques. The variation in wind direction with height is a more difficult problem with which to deal. The paper shows results from a pilot wind tunnel study which investigated two concepts to produce sheared twisted flow. Both of these concepts were successful, but the concept using a series of twisted vanes 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 economical solution from the point of view of both running and initial capital costs.