Experimental analysis of the flow field around a propeller with inclined shaft

The objective of the present study is to investigate, by means of velocimetric measurements, the flow field generated by a marine propeller running with inclined shaft. Measurements have been carried out on a scaled model of a propeller in the cavitation tunnel of UNIGE using Laser Doppler Velocimetry (LDV) and the acquired data have been post-processed applying the ensemble average technique. The propeller configuration includes shaft appendages as in a typical twin screw vessel configuration. The tests have been performed also without propeller, considering different velocities, in order to characterize the incoming flow field and analyse possible effects on propeller flow. The complete 3-D flow field has been measured considering four transverse sections at different longitudinal locations, from upstream to downstream of the propeller, focusing on the near field wake. A longitudinal plane containing the propeller shaft has been considered as well. A dedicated interpolation technique is presented to improve the spatial resolution of data and allow advanced analyses. Results allow analysing the main characteristics of the flow field, including the evolution of its main structures. The effects of non uniform inflow conditions caused by the oblique flow are analysed focusing on the dynamics of vortexes and in particular on the trajectories and strength of the vortexes.