Propeller performance on a model ship in straight and steady drift motions from single blade loads and flow field measurements

In the field of marine hydrodynamics, propeller operations in off-design conditions represent a challenging topic that has been increasingly attracting interest among industry and research institutions. Over the ship operating life, off-design conditions and the associated modifications of the propeller inflow are connected to a wide range of events such as degradation of the overall efficiency, amplification of unwanted side effects of propeller operations (pressure pulses, vibration and noise) and, ultimately, failure of the ship propulsion system. In this work, the performance of a propeller operating in off-design conditions is investigated by a comprehensive experimental activity aimed at synthesizing the cause-and-effect relation between the propeller loads and its inflow. To this purpose, two novel set-ups are employed: the first one is dedicated to the measurement of single blade loads, whereas the second, a boroscopic-based Stereo-PIV (SPIV) system, is focused on the inflow analysis. The overall measurement apparatus is installed on a twin-screw ship model. Experiments, carried out in the CNR-INM towing tank, consist of straight ahead and steady drift motions at drift angles ±13 and ±27. This test matrix is representative of weak and tight maneuvering conditions.