Aerodynamic Analysis around a C-Class Catamaran in Gust Conditions using LES and Unsteady RANS Approaches

Abstract

Wingsail is the propulsion mean adopted by the America’s Cup and C-class catamarans. This rig has improved aerodynamic performance with respect to conventional soft sails enhancing the yacht performance. However due to the higher forces acting wingsails, the yacht stability can easily be compromised especially in heavy gust wind conditions. The wingsail response to a gust has been then investigated performing numerical analysis in a C-class catamaran in downwind navigation conditions. Both a LES and an unsteady RANS approach were used for the simulations. The solutions given by the two approaches have been compared analyzing both the aerodynamic coefficients and the flow characteristics. The effect of the wind gust on the wingsail has been further investigated at different gust frequencies. Stall cells appear on the flap surface when the gust is taking into account affecting the wingsail aerodynamic performance.