Open Water Characteristics and Load Fluctuation of Propeller at Racing Condition in Waves

Abstract

In order to investigate the propeller characteristics at racing condition in waves, open water tests with a five bladed 15cm diameter propeller are carried out as to the following conditions. (1) In still water varying propeller immersion. (2) At the condition of forced heave oscillation in still water with two kind of propeller immersion. (3) In regular waves of different wave height with a shallow propeller immersion. (4) In irregular waves varying propeller immersion The effect of propeller immersion on the open water characteristics is studied, and the propeller load fluctuations at the experiments of (2)∼(4) are measured. It is shown that the propeller load fluctuations at racing condition in waves have two components, one is due to the orbital velocity of waves and the other is caused by the variation of propeller immersion, and that the smaller the immersion, the larger the latter component becomes. To analyse the nonlinear random phenomenon of propeller load fluctuations at racing condition in irregular waves, a mathematical model showing the relation between the propeller load and immersion is introduced and the analytical equation is derived for obtaining the spectrum of that phenomenon.