A generalised hybrid RANSE/BEM approach for unsteady flow effects in hull/propeller interaction

The hydrodynamics of a ship in prescribed motionis addressed by unsteady simulations using a hybridRANS/BEM solver. The interactive methodology com-bines a viscous-flow model addressing the flow aroundthe ship with a potential-flow model describing the loadsinduced by the vorticity generated at the propeller. Animplicit iterative procedure is provided in the time cy-cle through a body-force/effective inflow approach. Thepresent model is validated through comparisons about thevelocity flow-field and blade loads of numerical predictionsand measurements collected during an experimental cam-paign of a ship model in calm water moving in straightahead and steady drift motion. In particular, the nomi-nal tridimensional flow at the propeller disc is providedby the application of a stereo PIV technique, based on theuse of boroscopic equipment, whereas the transient singleblade loads are collected using a novel set-up adopting a 6-component multi-axial force transducer constrained at theroot blade itself. In spite of the inability of the model to ac-count for the blade boundary layer, the flow-field descrip-tion is detailed enough outside the propeller region whileassuring a limited computational burden related to meshgeneration. The present methodology represents a viablesolution to address the flow of maneouvring ships.