The wing-sail is an interesting idea for sailboats, and the last America’s Cup showed that its use is possible and very effective. At the University of Pisa it was decided to use this type of sail on the small boat realised for the inter-university race “1001 vele”.
A first wing sail has been used in 2013 with satisfactory results, but it was evident that high improvement in the performances can be obtained. The performances of this system are impressive, but the flow is complex and the number of geometrical parameters are very high.
In order to tackle this problem resort was made to a direct numerical optimization technique; this approach was attractive as it made it possible to address the problem systematically, and offered flexibility in the choice of the design variables. The approach is capable of meeting multi-disciplinary requirements but it requires, given the complexity of the flow, the use of a sophisticated CFD solver. STAR-CCM+ was then chosen for the aerodynamics evaluation in the optimization loop.
The optimization procedure is completely described in the paper, within the results and a critical analysis of the flow around the wing-sail, in order to have indication on the aerodynamics behaviour. This is for a better understanding of the physical aspects and also to give to the sailors the indications for the more efficient set-up.