Experimental investigation of propeller performance in straight and steady drift motion by single blade load measurements and boroscope-based SPIV

A marine propeller operating in off-design conditions isa challenging topic in marine hydrodynamics that has at-tracted a strong interest in the last decades from industryand research institutions. During actual ship operations,disturbances in the propeller inflow have a negative impacton a wide range of aspects: from reduced overall efficiencyup to the structural failure of the propulsion system. In thiswork, the relation between propeller loads and its inflowin off-design conditions is investigated by means of twonovel experimental set-ups developed to analyze each ofthese aspects, respectively an onboard system to measuresingle-blade loads, and a boroscope-based stereo-PIV sys-tem for the flow characterization. The latter methodologyallows underwater acquisitions and improves greatly uponthe design introduced by Pereira et al (2003). However, thisconcept introduces strong optical aberrations which have tobe dealt with appropriate algorithms. The whole apparatusis used for towing tank testing of a twin-screw model instraight-ahead and steady-drift conditions. Preliminary re-sults obtained in straight-ahead and steady-drift conditions(drift angle?= 13o) are reported to show the potentialof the developed measurement methodology for drawing acomprehensive picture of the propeller performance.