Design Optimization of Subcavitating Hydrofoils for America's Cup Class Yachts

The latest design for the America's Cup, which occurs every four years, represents a significant advancement in sailing technology. This design features a monohull structure equipped with two large foil arms that adjust based on wind direction. When the wind originates from one side, one foil remains submerged while the other rises above the water. The lift generated by these foils counteracts the boat's weight, allowing for improved stability and efficiency.

In addition to the lift, the design incorporates a rudder and a fighting force to manage wind resistance. The foils, made of solid steel and weighing 1.5 tons each, create a substantial moment that balances the sail's force, enabling the boat to sail upright rather than leaning over. This design enhances overall efficiency, although it also adds complexity to both operation and design.

To address these complexities, we focus on a specific aspect of the design, utilizing the Mach framework developed in my group. This framework allows for gradient-based optimization, which we can compute efficiently. We employ SNOs, with contributions from experts like President Michael Saunders, to facilitate this process. Geometry parameterization is necessary to modify the foil's shape, and subsequent mesh adjustments must occur automatically with gradients.

We utilize a Computational Fluid Dynamics (CFD) solver based on the Reynolds-Averaged Navier-Stokes (RANS) equations, acknowledging its lower fidelity in steady-state analysis. The adjoint solver is crucial in this process, building on the legacy of Professor Jimmy. Our research has produced numerous publications detailing this framework and its components. For illustration, we can begin with a simple geometric shape, such as a cylinder, which typically exhibits high drag and minimal lift, demonstrating the potential for improvement through our methods.