Investijation into Propulsion Factors in Waves with Overload Tests of a Container Ship

Abstract

Resistance tests and propulsion tests varing propeller load were carried out in regular and irregular head waves with a model of S-175 container ship. The test results were analysed with two formulae proposed by Adachi, et al. for the potential hull-propeller interaction in still water, one of which gave the resitance increase due to propeller load, G factor, and other gave the wake factor, 1-w. The results are as follows; (l) The formulae fit well not only for the results in still water but also for those in waves. G and 1-w are then presensed with the propeller load, the wake factor at zero propeller load, 1-w_0, and two coefficients common both in still water and in waves. (2) The difference between the resistance at zero propeller load and one without propeller, R_c-R_0, and the wake factor at zero propeller load, 1-w_0, in waves are shown. They are influenced by wave and ship motions. (3) The thrust deduction coefficient of conventional definition, t, does not give a consistent prediction of propulsive performance in waves when the propeller load is heavy. A rational power prediction method of a ship in a seaway is proposed further using the formulae. Examples are presented for the container ship and a bulk carrier.