EXACT MODELING OF TRAILING VORTICITY IN PANEL METHOD FOR MARINE PROPELLER

Hydrodynamic modelling of the trailing vortex wake of a propeller is one of the key factors in the development a consistent propeller theory: the influence of the wake flow modelling becomes significant for a propeller operating below design point, when the wake pitch is small and the trailing vorticity tends to be packed close to the propeller disc. Wake flow modelling is also important for a correct prediction of cavitation inception, especially of the interest is in the tip vortex flow characterization. Another field of interest is the analysis of the mutual interactions between propellers and others components, as in the case of propeller/rudder, propeller/propeller and pod configurations. The present work presents three main theoretical/numerical techniques adopted in the propeller surface panel method developed at the University of Genoa. The first is an iterative pressure Kutta condition able to ensure a zero pressure jump along the trailing edge. The second is a fully numerical wake alignment algorithm (instead of mixed numerical experimental algorithm) able to accurately model the highly rolled-up regions. The predicted wake shapes are shown to converge and to be consistent with those predicted with other methods, on a number of experimental/theoretical studies made on different wings. Finally, the wake alignment algorithm is coupled with the boundary element method in order to estimate wing and propeller bound/trailing vortex interaction. Predicted forces, circulation distributions, and tip vortex trajectories are shown to agree well with those measured in experiments, in the case of an elliptical wing, for which a large series of reference data are available and in the more particular case of a marine propeller.