CFD sensitivity studies of turbulent model, grid, roughness and scale effect for full scale ship performance estimation

Abstract

The performance of full scale ship is commonly estimated from results of model scale analysis as ITTC correction methods. Recently, full scale CFD is also being used for ship performance estimation due to less scale effect. However, full scale CFD is difficult to validate the results because actual ship performance includes the effect of complex external environment forces during sea trial or operation, but it is quite difficult to completely separate the terms of external forces. Full scale CFD results could be only validated as comparing with the experiment results or corrected data of sea-trial. Because of these constraints, it is important to understand the CFD sensitivity and the difference according to the variables in the numerical analysis method and scheme to improve the accuracy of numerical simulation. Firstly, to grasp the difference of resistance and propulsion performance estimation according to scale, the resistance and self-propulsion CFD results of a bulk carrier at model and full scale were compared with experiment results. The correction method is referred to the model test procedure of KRISO based on ITTC method. As second phase, in the resistance analysis of a full scale product carrier, the sensitivity of turbulence model and grid was investigated, and the effect of the surface roughness was also studied at model and full scale. As turbulent model, ĸ-？ realizable, ĸ-？ standard, ĸ-ω SST and Reynolds Stress model were applied with 1st and 2nd order temporal scheme. For grid sensitivity study coarse, medium and fine mesh were compared at ĸ-？ realizable and ĸ-？ standard. In case of wall roughness condition, three different roughness heights were applied including 150μm of new building ship’s roughness. Furthermore, the propeller open water performance of full and model scale was calculated at ĸ-？ realizable and ĸ-ω SST transition. Finally, the self-propulsion analysis of full and model scale ship was performed as virtual disk method combined with CFD results of the full scale POW. The calculated results were compared with the full scale performance derived from the experiment results of scaled model ship. ？ 2019 by the International Society of Offshore and Polar Engineers (ISOPE).