Development and Validation of a Computational Fluid Dynamics Hydrodynamic Model of the Stewart 34 for Velocity Prediction Program Applications

The prediction of the hydrodynamic behavior of sailing yachts is a key component of modern yacht design, particularly to assess the theoretical performance of a design through a velocity prediction program. The increasing computational power now offers an alternative to towing tank testing: computational fluid dynamics. The work conducted on the development and validation of a computational fluid dynamics hydrodynamic model of the Stewart 34 sailing yacht for velocity prediction program applications is presented in this report. An empirical resistance model has initially been developed based on the Delft Systematic Yacht Hull Series. The method has been described and its limitations highlighted, the main ones being the resistance prediction in semi-displacement mode and the side force prediction at high leeway angle. The method is however reliable for common designs in displacement mode and is particularly efficient since only a few design inputs are required. In a second time, the use of the Rankine source panel code FS-Flow led to a computational fluid dynamics hydrodynamic model of the Stewart 34, validated against an experimental benchmark, as done for the empirical resistance calculations. Instabilities in the panel code at high Froude numbers resulted in a loss of accuracy. Furthermore, the panel code did not prove suitable at high leeway angles. FS-Flow appears to have some limitations when handling the hydrodynamic model of sailing yachts; its intended use primarily being the comparison of ship designs. A total of three velocity prediction programs have been developed. An empirical 4 degrees of freedom one enabled to ascertain the test matrix for the Stewart 34. A second 4 degrees of freedom one was realized with WinDesign to provide a reference and comparison with the final 6 degrees of one done using FS-Equilibrium. This final velocity prediction program gathers the experimental hydrodynamic and aerodynamic models and was validated against available upwind full-scale data to ensure its reliability. A complete performance prediction for the Stewart 34 was therefore achieved based on experimental data, mostly focussing on the hydrodynamic model ascertained using both empirical and computational fluid dynamics methods, thus meeting the objectives set for this project. Finally, areas of further improvement and future work have been recommended.