Numerical modeling of Fluid-Structure Interactions (FSI) effects of soft sails has now been studying for a few years [1, 2, 3]. FSI models have been compared and validated with experiments [4, 5], and they are now also applied to several optimization problems [6, 7]. However, due to the very complex aero-elastic phenomena of yacht sails, such nonlinear FSI computations are still challenging. The modeling difficulties can concern the fluid and structural solvers, in addition to the coupling strategy. Structural solvers are usually based on finite element methods, while for the flow solver, inviscid models [8] are widely used, because of their fast computing time in comparison to the viscous flow ones [9]. In many cases these computations are still very expensive, in addition to sometimes having convergence problems. As a result, they are used little or not at all in industrial projects, and there is a real need today, for some companies, to have fast and robust FSI yacht sails models, in order to have precise design processes, in a moderate engineering time.
Following the FSI model concern, the present paper focuses on an original fast and robust approach to compute FSI effects of a yacht mainsail. Specifically, the proposed strategy uses the lifting line theory (LLT) [10] combined with a semi-analytical Chebyshev–Gauss integration [11, 12, 13], that allows efficient aerodynamic sail pressures computations. Regarding the structural part, the proposed method uses the Abaqus T M finite element software. A quasi-static resolution with a dynamic backward Euler scheme [14] is carried out. It enables to help the convergence of nonlinear static equilibrium owing to dynamic relaxation and the natural damping of the scheme. A standard Newton-Raphson nonlinear static resolution is then performed to ensure exact static convergence. The sail membrane is modeled by shell elements and a specific thickness treatment is employed in order to make easier the nonlinear sail FSI resolution solving [15].
The present work is applied within the “Solid Sail 2.0” project, which makes it possible to compute sail FSI effects on a real industrial case problem. Indeed, this project is led by the French “Chantiers de l'Atlantique” company, and its purpose is to develop a rigid sail composed of articulated composite panels. The sail lifecycle is therefore significantly increased and it is then possible to consider this type of sail for large merchant ships.