A study on ship performance in waves using a RANS solver, part 2: Comparison of added resistance performance in various regular and irregular waves

Abstract

Commercial ships frequently operate under irregular sea conditions; hence, their performance must be estimated through simulations in a more realistic environment. To date, a number of experiments and numerical studies have been conducted using regular waves to estimate added resistance. In this study, the performance of the KVLCC2 hull considering the added resistance in various regular and irregular waves was evaluated using an unsteady Reynolds-averaged Navier–Stokes solver. Resistance and motion responses were observed for regular waves with various wavelengths, regular waves with various wave steepness, and bichromatic waves superposed with regular waves. The change in resistance performance and damping with respect to motion response based on wave height was analyzed. An irregular wave corresponding to the joint North Sea wave project spectrum under sea state 6 was derived; based on this derived wave, the added resistance in irregular waves was estimated. The added resistance was compared with the estimated value using the spectral method, which was also employed to derive the added resistance under the target sea state using regular wave results. The estimated values differ from the direct calculation results owing to the nonlinearity of resistance in the irregular wave. However, the motion responses showed a similar tendency to those of the regular wave (except for those in the proximity of natural frequency that were relatively large and could be influenced by the wave height), as observed when various wave steepness values were used.