## 6 Conclusions  
In this study, numerical simulations of resistance tests were conducted for the KCS container ship model at an even keel and four trims to determine the effect of trim on the total resistance in confined and shallow water using two turbulence models, i.e., RKE and SSTKO. The mathematical model was based on the RANS equations discretized by the FVM method, while the VOF method was used to determine the free surface position. Verification and validation studies were carried out for the ship model at an even keel to assess the numerical uncertainty and relative deviations from the experimental data. A detailed analysis of the flow around the hull is given, including wave patterns and wave elevations along the hull, the distribution of the hydrodynamic pressure, and tangential stresses for all analyzed trims. Based on the conducted study, the following conclusions are drawn:  
* The obtained results have shown the importance of the turbulence model selection, as in this study, the total resistance obtained using the RKE turbulence model is closer to the experimental value than the one obtained using SSTKO. * By assessing the effect of trim on the total resistance it was found that it is possible to achieve a reduction in total resistance at trims by bow in confined and shallow water. The largest decrease in the total resistance was obtained for a trim of 0.4\({}^{\circ}\), and it amounts to \(-\)3.05%. * It was shown that pressure resistance is more sensitive to trim variations in comparison to frictional resistance. For a trim by bow, there is a reduction in pressure resistance compared to one at an even keel, which contributed to an overall decrease in the total resistance of the ship model at those trims. On the other hand, there is a significant increase in pressure resistance for a trim by stern, resulting in higher total resistance. It can be concluded that the trim has a significant impact on altering the pressure resistance, while its effect on frictional resistance is also present but to a lesser extent. * To analyze the effect of trim on the total resistance components, double\(-\)body simulations were also conducted using the aforementioned turbulence models. The results showed that by using the SSTKO turbulence model the part of the wave resistance in the total resistance is notably larger in comparison to results obtained using RKE. * The frictional resistance forms the largest part of the total resistance, followed by viscous pressure resistance, while the part of the wave resistance is the smallest. The part of the frictional resistance in the total resistance increases for trims by bow. * The viscous pressure resistance increases for trims by bow and decreases for trims by stern in comparison to one at an even keel. * The most significant differences can be observed for wave resistance, whose part in the total resistance decreases for trims by bow. The increase in the total resistance for the largest analyzed trim by stern of \(-\)0.4\({}^{\circ}\) is mainly caused by an increase in the wave resistance. * The effect of trim on the form factor is almost negligible. Although this study showed a decrease in the total resistance at trims by bow and an increase at trims by stern, the trend  
**Author Contributions:** Conceptualization, I.M., B.A. and N.D.; methodology, I.M., B.A. and N.D.; software, I.M., B.A. and C.G.G. ; validation, I.M., B.A., N.D. and C.G.G. ; formal analysis, I.M., B.A., N.D. and C.G.G. ; investigation, I.M., B.A., N.D. and C.G.G. ; resources, N.D.; writing--original draft preparation, I.M., B.A., N.D. and C.G.G. ; writing--review and editing, I.M., B.A., N.D. and C.G.G. ; visualization, I.M., B.A. and C.G.G. ; supervision, I.M. and N.D.; project administration, I.M., N.D. and C.G.G. ; funding acquisition, N.D. All authors have read and agreed to the published version of the manuscript. This study was funded by the Croatian Science Foundation under project IP-2020-02-8568. Not applicable.