In general, the speed power performance of ships is optimized for the specific speed and draught in accordance with contract condition. But, this condition may not be always the same as the actual operating condition. Therefore, in order to reduce the fuel consumption practically, it is necessary to optimize the performance under various conditions considering the actual voyage. This is the reason that the trim optimization covering various operating profiles becomes the main issue in reducing fuel oil consumption.
In this paper, a numerical study is carried out to optimize trim using the computational evaluation system(SoLuTion) developed by Samsung Heavy Industries Co. (SHI) with variation of draught, ship speed and voyage trim. In order to get a more accurate solution in resistance and propulsion performance, the Reynolds-averaged Navier-Stokes(RANS) equations including the Volume Of the Fluid (VOF) method by Hirt and Nichols (1981) for the free-surface boundary condition and the moving mesh technique for the propeller rotation effect are employed as governing equations. Reynolds Stresses Model (RSM) with the wall function is applied to the turbulence model for turbulent flow computation. Through the present study, the following three factors should be considered to evaluate the accurate speed performance quantitatively by varying the draught, speed and voyage trim. First, the distance from hull surface to the first grid point should be adjusted to eliminate the effects of frictional resistance by the grid size according to variation of speed. Second, the grid system should be generated in order to avoid the grid dependency on variation of draught Finally, the running trim and sinkage of the voyage conditions should be considered. The results of the trim optimization performed numerically are well-matched with the towing test results conducted at Samsung Ship Model Basin(SSMB). As the results of this study, it is confirmed that SoLuTion is a useful and efficient tool for the trim optimization and the provided optimum trim will be able to contribute to fuel savings under the operating conditions.
