Experimental survey on the wake of the OSHIMA ship model using the SPIV technique Part 2. Propeller wake analysis: phase locked measurements

The object of the second phase of the collaboration contract was to investigate the effect of energy saving devices (ESD), characterized by different geometries, on the wake hydrodynamics of the OSHIMA ship model with the propeller in service. In particular, velocity measurements at a plane close to the propeller have been performed for one pre-swirl stator (PSS) and three ducts placed upstream the propeller position. As for the previous part, the goal was to document the draught influence on the effectiveness of the ESD for two loading conditions. To this end, measurements were repeated in full load and ballast conditions. A CNR-INM stock propeller, namely E619, has been used, working at the propulsive rotation speeds as measured during dedicated self-propulsion tests. Using the in-house designed, underwater probe, Stereo-PIV (SPIV) measurements have been carried out and populations of instantaneous 3C-2D vector fields have been collected. 12 different propeller angular positions have been investigated, in step of 7.5 angle degrees, covering a 90° sector of the propeller plane. Statistical quantities have been calculated to provide information suitable to describe in details the hydrodynamic effects of the ESDs on the propeller and to perform comparison with CFD data.