Experimental and numerical wind tunnel investigation of the aerodynamics of upwind soft sails

The present paper reports an experimental/numerical study about the aerodynamics of sails in upwind conditions. This work is part of a wider research frame carried out in the recent years at Politecnico di Milano, involving numerical, wind tunnel and full-scale studies on the aero-hydrodynamics of sailing yachts. The experimental apparatus adopted in this work is the scaled-version of the full-scale setup adopted in the Sailing Yacht Laboratory (SYL) at the same institutions. More specifically, soft sails were tested in wind tunnel in close hauled conditions, properly equipped with thin and soft pressure strips at different sections of head and main sail. Therefore, simultaneous data about distributed pressure, aerodynamic forces and 3D flying shapes were gathered. Fine trimming were investigated during the tests to study the different effect on pressure distribution, performance and sail shapes. The measured sails geometry about the same conditions, fed the steady numerical simulations, based both on Vortex Lattice Method and Reynolds Averaged Navier Stokes equations, for comparison and validation. With regard to the latter, a sensitivity analysis on the simulation parameters was also reported in comparison to experimental results. Aim of this work was to improve the state-of-the-art with an extensive set of combined measurements and computations of different nature and objectives in order to provide a holistic view on the upwind sails aerodynamics.