Two-Dimensional CFD-Based Parametric Analysis of Downwind Sail Designs

Abstract

This paper presents results from a Computational Fluid Dynamics (CFD) based parametric design study of two-dimensional downwind sail sections. By varying draft and camber a range of sail shapes are generated that cover the typical range of an America’s Cup Class (ACC) downwind sail inventory. In order to reduce simulation times only a solitary downwind sail is used, i.e., the influence of the mainsail is ignored. One series of simulations is also carried out with a mainsail included to establish the impact of the mainsail’s presence and to determine whether or not downwind sails can be designed in two-dimensions at least whilst ignoring the influence of the mainsail. Results show that very high lift coefficients (2.1-2.5) can be obtained for two-dimensional downwind sail sections. These lift coefficients are considerably higher than lift coefficient values (1.0-1.7) typically used in Velocity Prediction Programs (VPPs) indicating that real downwind sails experience three-dimensional effects that hinder their performance considerably.