Rudder-Propeller Interaction: Analysis of Different Approximation Techniques

This paper addresses the problem of the numerical evaluation of the forces exerted by rudder/propeller complex; in particular, considering the common framework of RANS computations, different possible approximations of the propeller effect are taken into account, starting from the simplest uniform actuator disk and moving successively to an actuator disk with radial distributions of axial and tangential forces and then to a set of unsteady body forces, computed by a panel method, representative of the rotating pressure field of the propeller. All the results, in terms of global mean forces on the rudder and of fluctuating components and flow field, are compared to the full RANS computations and to the experimental results in model scale for the same configuration. The comparison of the results allows to identify the merits and the shortcomings of the different approaches, in order to select the best ones for the various possible applications, having in mind the necessity to keep the computational efforts to a reasonable level during the design phases.