https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Mon, 13 Jul 2026 06:50:44 GMT 2026-07-13T06:50:44Z http://hdl.handle.net/10985/8697 On the Uncertainty of CFD in Sail Aerodynamics VIOLA, Ignazio Maria; BOT, Patrick; RIOTTE, Matthieu A verification and validation procedure for yacht sail aerodynamics is presented. Guidelines and an example of application are provided. The grid uncertainty for the aerodynamic lift, drag and pressure distributions for the sails is computed. The pressures are validated against experimental measurements, showing that the validation procedure may allow the identification of modelling errors. Lift, drag and L2 norm of the pressures were computed with uncertainties of the order of 1%. Convergence uncertainty and round-off uncertainty are several orders of magnitude smaller than the grid uncertainty. The uncertainty due to the dimension of the computational domain is computed for a flat plate at incidence and is found to be significant compared with the other uncertainties. Finally, it is shown how the probability that the ranking between different geometries is correct can be estimated knowing the uncertainty in the computation of the value used to rank. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8697 2013-01-01T00:00:00Z VIOLA, Ignazio Maria BOT, Patrick RIOTTE, Matthieu A verification and validation procedure for yacht sail aerodynamics is presented. Guidelines and an example of application are provided. The grid uncertainty for the aerodynamic lift, drag and pressure distributions for the sails is computed. The pressures are validated against experimental measurements, showing that the validation procedure may allow the identification of modelling errors. Lift, drag and L2 norm of the pressures were computed with uncertainties of the order of 1%. Convergence uncertainty and round-off uncertainty are several orders of magnitude smaller than the grid uncertainty. The uncertainty due to the dimension of the computational domain is computed for a flat plate at incidence and is found to be significant compared with the other uncertainties. Finally, it is shown how the probability that the ranking between different geometries is correct can be estimated knowing the uncertainty in the computation of the value used to rank. http://hdl.handle.net/10985/8685 Upwind sail aerodynamics : A RANS numerical investigation validated with wind tunnel pressure measurements VIOLA, Ignazio; BOT, Patrick; RIOTTE, Matthieu The aerodynamics of a sailing yacht with different sail trims are presented, derived from simulations performed using Computational Fluid Dynamics. A Reynolds-averaged Navier-Stokes approach was used to model sixteen sail trims first tested in a wind tunnel, where thepressure distributions on the sails were measured. An original approach was employed byusing two successive simulations: the first one on a large domain to model the blockage due to the wind tunnel walls and the sails model, and a second one on a smaller domain to model the flow around the sails model. A verification and validation of the computed aerodynamic forces and pressure distributions was performed. The computed pressure distribution is shown to agree well with the measured pressures. The sail surface pressure was correlated with the increase of turbulent viscosity in the laminar separation bubble, the flow reattachment and the trailing edge separation. The drive force distribution on both sails showed that the fore part of the genoa (fore sail) provides the majority of the drive force and that the effect of the aft sail is mostly to produce an upwash effect on the genoa. An aerodynamic model based on potential flow theory and a viscous correction is proposed. This model, with one free parameter to be determined, is shown to fit the results better than the usual form drag and induced drag only, even if no friction drag is explicitly considered. A novel method similar to marching technique was used to model wind tunnel tests. ► Sail trim criteria based on their interactive effect are identified. ► Areas of separated flow were characterised. ► Local flow field was correlated with sail surface pressures. ► An aerodynamic model based on potential flow with viscous correction is proposed. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8685 2012-01-01T00:00:00Z VIOLA, Ignazio BOT, Patrick RIOTTE, Matthieu The aerodynamics of a sailing yacht with different sail trims are presented, derived from simulations performed using Computational Fluid Dynamics. A Reynolds-averaged Navier-Stokes approach was used to model sixteen sail trims first tested in a wind tunnel, where thepressure distributions on the sails were measured. An original approach was employed byusing two successive simulations: the first one on a large domain to model the blockage due to the wind tunnel walls and the sails model, and a second one on a smaller domain to model the flow around the sails model. A verification and validation of the computed aerodynamic forces and pressure distributions was performed. The computed pressure distribution is shown to agree well with the measured pressures. The sail surface pressure was correlated with the increase of turbulent viscosity in the laminar separation bubble, the flow reattachment and the trailing edge separation. The drive force distribution on both sails showed that the fore part of the genoa (fore sail) provides the majority of the drive force and that the effect of the aft sail is mostly to produce an upwash effect on the genoa. An aerodynamic model based on potential flow theory and a viscous correction is proposed. This model, with one free parameter to be determined, is shown to fit the results better than the usual form drag and induced drag only, even if no friction drag is explicitly considered.