Sailing, aerodynamics in waves - new paper

Prediction and analysis of added hydrodynamic resistance in waves is an established research topic, with several accepted methods, but the study of sail aerodynamics in waves is an open research area. The unsteady aerodynamic behavior of sails in waves can greatly influence the performance of a yacht, by providing increased driving force in some conditions, but decreased driving force in others. SSPA and Chalmers are cooperating in the Sports & Technology initiative, with several research projects in sailing. The leading journal Ocean Engineering has recently published a paper titled “CFD prediction of steady and unsteady upwind sail aerodynamics”.

SSPA is using state-of-art technology to help advance the aero- and hydrodynamic analysis of sailing yachts in realistic conditions, accounting for waves and the yacht motions that occur because of these. The unsteady aerodynamic behavior of sails in waves can greatly influence the performance of a yacht, by providing increased driving force in some conditions, but decreased driving force in others.

A verification and validation for steady conditions is presented, demonstrating the quality of the CFD (Computational Fluid Dynamics) simulations, with low numerical uncertainty and excellent agreement with experimental data. An innovative approach, based on CFD, was used to improve the understanding of experimental conditions, reducing uncertainty in the comparison between numerical simulations and experimental results, demonstrating the potential advantages of combining CFD and experimental/model testing.

In addition, a comprehensive sensitivity study is presented, investigating the impact of numerical modelling choices on the predicted forces. The results from this study can be used in other application, where flows with strong curvature and separation at low speeds need to be studied. The technique used to resolve the motion of the sail plan could also be applied to other applications, such as seakeeping or shallow water manoeuvring.

The paper

The published paper can be found online at the journal Ocean Engineering: “CFD prediction of steady and unsteady upwind sail aerodynamics”

The authors

PhD student Adam Persson (SSPA), Lic. Eng. Rickard Lindstrand (Chalmers), Dr. Sara Muggiasca (Politecnico Milano) and Prof. Lars Larsson (Chalmers).

Contact

PhD student Adam Persson, adam.persson@sspa.se

Illustration

Instanteous force distribution for a pitching sail. Red areas indicate high force, blue indicates zero force. Grey areas show flow separation.