Interaction of the vortex systems detached from a propeller with a rudder installed in its wake is investigated by CFD. The correct prediction of this phenomenon is of great interest in naval hydrodynamics research, it being the source of irradiated noise and vibratory loads. The phenomenology is addressed by simulating a single bladed propeller (INSEAN E779A) and a rudder characterized by a rectangular plane area and symmetric sectional shape (NACA0020 profiles). The main focus is on the hydro-loads developed by the rudder and their correlation with the different phases of the interaction of the tip vortex with the rudder. The phenomenon is also investigated, through a preliminary computation on a coarser mesh, on the actual propeller geometry (4-bladed).

The flow in the stern region of a fully appended hull is analyzed by both computational and experimental fluid dynamics. The study is focused on the velocity field induced by the rotating propellers. Measurements have been performed by laser Doppler velocimetry (LDV) on the vertical midplane of the rudder and in two transversal planes behind the propeller and behind the rudder. In the numerical approach, the real geometry of the propeller has been considered. To this purpose, a dynamic overlapping grids method has been used, which is implemented in the unsteady Reynolds averaged Navier-Stokes equations (URANSE) solver developed at INSEAN. Uncertainty analysis has been performed on both data sets and the results from the two approaches are compared. The agreement between the two data sets is found to be good, the deviation in the velocity and vorticity fields lying within the evaluated uncertainties. Numerical data allowed the analysis of further details of the flow that could not be measured, like load conditions of the single blades, interaction of the propeller wake with the rudder, and pressure oscillations induced by the propeller on the vault of the stern.