A numerical study on self-propulsion performance in regular waves and power prediction in irregular waves

Abstract

Several numerical studies have been conducted to investigate the methods for self-propulsion performance that changes with the wave conditions using KVLCC2. On comparing the propulsive factors with respect to the wave conditions, self-propulsion performance was observed to undergo changes. It showed that the propulsion efficiency decreases when the added resistance that increases in regular waves, which leads increasement of the required horsepower. Power prediction in the irregular waves was done using the spectral methods as an indirect method, which derives the increase in variables in a target sea state with a quadratic transfer function and wave spectrum. The four spectral methods were considered depending on the parameters used. These can be divided into the methods (SA, TNM, QNM) that use the assumed self-propulsion factors and a proposed method that considers the changes of factors in wave conditions. Consequently, when considering the changes in the self-propulsion factors in the sea state wherein the wave height increases, the power was estimated to be relatively low. This indicates that with increasing wave height, the linear relationship between the variables and the wave height is degraded. This study proposes the necessity of considering the effect of waves on self-propulsion to estimate the realistic power of ships.