Predicting thrust loss of ship propellers due to ventilation and out-of-water effect

Abstract

This paper presents a propeller ventilation model that is tuned on experiments performed in open water condition in a towing tank. The main purpose of performing the experiments was to obtain more data at higher advance numbers for validation purposes and to make a calculation model for thrust and torque loss due to free surface proximity. Tests were performed at different draughts. For each draught the propeller were tested at the different propeller speeds 𝑛� = 9, 12, 16 𝑎�𝑛�𝑑� 16 𝐻�𝑧� at advance number in the range from J=0 to J=1.0. The different advance numbers were obtained at different propeller speeds so that for the same advance number different propeller thrust values was tested, so that the effect of propeller loading can be seen independently from speed of advance J. The main focus in this paper is to explain and validate a prediction model for thrust loss due to ventilation and out-of-water effect.