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SUMMARY This paper deals with the hydrodynamic sideforce production of a wind-assisted ship. The subject is introduced in physical terms, and the importance of the hydrodynamic sideforce is established, before classical models are reviewed. Finally, the complications arising from diverse appendage topologies are discussed, and a theory for zero-aspect ratio lifting surfaces is discussed. The paper concludes with a short summary of ongoing work.

Wind-assisted ship propulsion is under study at the Delft University of Technology. This alternative propulsion is gaining attention due to increased concern for the environment. For designers who are considering the potential benefits of this new option, a well-founded performance prediction tool is a key prerequisite. Together with Politecnico Milan, the TU Delft is developing such a tool, which will allow for inexpensive assessment of wind-assist concepts using regression based force models. Reynolds-Averaged Navier Stokes (RANS) simulations will be a primary tool during this study. The advent of the numerical towing tank brings possibilities but also new challenges. The predominance of large, separated flow structures in the wake of the sailing ship, and the particular interest in the lateral force generation of the hull, points to a conscientious grid verification study. Here, it is sufficient to achieve parity among uncertainty contributions within the larger context of the project. Diverse procedures are available for evaluating the numerical uncertainty of a RANS simulation. Principal methods were defined and implemented for verification cases at leeway angles of 0, 9, and 20 degrees. The uncertainty for lateral force at 9 degrees leeway for the base grid (2E6 cells) was estimated to be 8.3%.

This paper deals with the hydrodynamic sideforce production of a wind-assisted ship. The subject is introduced in physical terms, and the importance of the hydrodynamic sideforce is established, before classical models are reviewed. Finally, the complications arising from diverse appendage topologies are discussed, and a theory for zero-aspect ratio lifting surfaces is discussed. The paper concludes with a short summary of ongoing work.