Hugo Nicolas, PhD student, Platon Team
Title: Development of a Velocity Prediction Program for the Design Optimization of Hydrofoiling Sailboats
Abstract: From sport to the marine industry, hydrofoils represent a great step forward to improve ship performance, seakeeping, and reduce energy consumption. With that, hydrofoil design has become a crucial part of ship design, requiring state-of-the-art tools to capture the complex and multidisciplinary physics involved. Within the design cycle, hydrofoil design is typically performed in parallel with yacht simulations maximizing a given objective function, using trimming parameters. In the context of racing sailboats, these simulation tools are called velocity prediction programs (VPPs). To accelerate the design cycle and its result, the present work proposes a novel approach for carrying out hydrofoil design and yacht trimming simultaneously. For that purpose, a steady-state system-based VPP is developed using gradient-based optimization. The simultaneous analysis and design architecture is used for conducting multidisciplinary design optimization. The lifting surfaces are modeled numerically using the vortex lattice method of OpenAeroStruct. An antisymmetry condition is implemented and differentiated within OpenAeroStruct for modeling the free surface. Ventilation and cavitation are addressed through design constraints. The VPP is applied to an America’s Cup AC75 monohull, showing great correlation with data measured during the 36th America’s Cup races. The optimization problem used for validation involves 25 design variables. The optimization of hydrofoil design improves the velocity made good by 7.52% (respectively 5.56%) compared to the baseline for the upwind (respectively downwind) case. Sources of discrepancy and improvements in the numerical models are identified and discussed. All in all, this work validates and justifies the development of the tool. After further validations, the tool should be ready to be used for addressing design optimization of the AC75 lifting surfaces.
