An experimental study on the open water characteristics of a ship propeller in waves

This paper deals with the assessment of the propeller performances in waves, by means of experimental open water tests. The focus of this study is on the propeller behaviour, neglecting, at this stage, the interaction with the hull dynamics. The towing tank experiments are carried out in calm water deeply immersed (nominal condition), and then repeated by reducing the head at the propeller tip, up to the point where ventilation and cavitation phenomena occur. The regular waves tests are conducted for several wave frequencies and amplitudes up to the complete emersion of the blade in correspondence of the wave trough. The averaged values of the propeller characteristics are compared to the ones obtained at nominal condition, and their time history is analysed with respect to the wave profile (i.e. local head of water at the propeller). Attention is given to frequency domain analyses and to the presence of hysteretic phenomena. The entire range of advance coefficients is investigated, i.e. from bollard pull up to windmilling condition. The outcomes of the current study are meant to support the development of a numerical method for the evaluation of the effective propeller characteristics in waves, in view of further analyses taking into account the effects of hull dynamics.