Downwind sails aerodynamic analysis

RANS code has been applied to an America’s Cup Class Yacht to investigate sailing performance in downwind configuration. Apparent wind angles at 45°, 105° and 120° are reported, sailed with mainsail and asymmetrical spinnakers. Numerical results are in good agreement with wind tunnel data. A large mesh investigation have been performed, ranging from 60.000 elements up to 37 million elements, which shows a converging trend to the experimental values with differences smaller than 3% in both lift and drag. The most commonly used turbulence models in sails applications have been tested and the results are presented here in two meshes with 1 million elements and 6.5 millions, respectively. All models overestimates forces more than solving the Navier-Stokes system without any additional equations, hence turbulence models do not increase solution accuracy according to these results. I. M. Viola and F. Fossati