Dynamic simulation of two sailing boats in match racing

This paper describes current progress made towards the realization of a match-racing simulator. The aim of the project is to be able to simulate and to modify typical situations while introducing quantifiable data for strategic and tactical analysis. The fundamental model consists of six fully coupled equations of the dynamics of two boats. The largest possible number of variables is taken into account, even though some are initially approximations. The influences of the three attitude angles on the hydrodynamic forces are taken into account using the ‘experiment planning method’ applied to towing-tank tests. For the aerodynamics, empirical models (for example IMS) are adopted. The interaction between the two boats is obtained by representing the sail perturbation by means of a single horseshoe vortex and a self-preserved viscous plane wake. The simulator has a modular structure, which allows the progressive improvement of each part as studies and knowledge advance. Comparisons with calculations of three-dimensional flows and with wind tunnel measurements validate the interaction model. The results presented show a satisfactory agreement with the polar velocity diagram available for the studied boat, even if more reliable trials at sea are needed, with measurements of boat behaviour, wind and sea state. Simulations allow us to quantify the relative influence of model coefficients on boat behaviour. Thus it is possible to identify which factors must be improved first. Tacking simulations are used to illustrate this possibility. To conclude, an example of the practical use of the simulator is presented by comparing two tactical scenarios for the final part of the upwind leg.