On the scale effect of thrust deduction in a judicious self-propulsion procedure for a moderate-speed containership

Abstract

We studied the scale effect of the thrust deduction factor on an innovative self-propulsion procedure. In contrast to the International Towing Tank Conference (ITTC) committee documents, which adopt a skin friction corrector and also state that the thrust deduction factor is the same for both the model and full scales, complex interaction remains unresolved. Since the skin friction corrector is always calculated by an equation, to date no verifications of this equation have been published. In addition, the scale effect of the thrust deduction factor has seldom been studied because it is minor compared to that of the wake fraction. In the first section of this paper, the existence of the scale effect on the thrust deduction factor is proven and the misinterpretation of the equality is highlighted. Second, a balanced self-propulsion procedure, which does not use the skin friction corrector to isolate the propeller loading effect is proposed and compared to the conventional standard ITTC procedure. The study derived a simplified model for predicting the full-scale values for the thrust deduction factor correction. The new procedure was applied to a moderate-speed containership by CFD software and several characteristics were demonstrated. The scale correction model was verified from the computational results.