Seol Nam

This study aims to investigate the influence of wheel configurations on hydrodynamic resistance of an amphibious vessel through experiments and simulations. To evaluate the resistance performance associated with wheel attachments, three configurations were examined: vessel without attachments, with caterpillars, and with both caterpillars and shoe−paddles. A comprehensive series of computational fluid dynamics (CFD) simulations were conducted for these attachment types, complemented by experimental validations. The Volume-of-Fluid (VOF) model was employed in CFD simulations to capture the free surface movement, and the Dynamic Fluid–Body Interaction (DFBI) model was adopted to represent the two-degree-of-freedom motion of the vessel, specifically trim and sinkage. The total resistance derived from CFD simulations was calculated across a range of Froude numbers (Fns), including the design speed of the target vessel, and validated through model tests conducted in a wave basin equipped with a towing facility. The analysis indicated a general increase in resistance when attachments were added to the amphibious vessel. Remarkably, at the design speed (Fn = 0.27), the total resistance with both caterpillars and shoe−paddles exceeded that of the configuration without any attachments by more than 75.7%. These results provide crucial insights for the preliminary design stage of amphibious vessels, particularly those intended for marine debris collection in hard-to-reach areas.

This paper explains the evaluation process of seakeeping performance for small vessels using a CFD-modified potential (CMP) model, a hybrid simulation model that modifies the damping ratio with computational fluid dynamics (CFD) after analyzing ship motion based on the linear potential theory. From the result of the motion analysis using the CMP model, the seakeeping performance of a small vessel (a barge here) was evaluated on the basis of the single significant amplitude (SSA) under the sea states 2~4. The results of the motion RAOs and seakeeping performance evaluation were verified through comparison with the results obtained by performing model tests and potential flow programs only. In all sea states, the relative errors (compared to the experiment) of roll motion using the CMP model were relatively small compared to the results using the potential flow program and tended to decrease more as the sea state increased. On the other hand, the results of pitch motion using the CMP model were underestimated in all sea states compared to the experiment. However, it is seen that they are relatively closer to the experiment compared to the results using a potential flow program only.

This study proposes a computational fluid dynamics (CFD)-modified potential (CMP) model. This hybrid model uses linear potential theory with a corrected damping ratio obtained from CFD simulations to analyze the seakeeping performance of a small vessel. According to the analysis procedure of the proposed model, a motion analysis, including the prediction of the roll and pitch damping ratio of a small barge, was conducted; to verify reliability; the results were compared to those of an experiment performed in a physical tank. The relative errors in the experiment for peak amplitude in the roll motion response amplitude operators (RAOs) using the CMP model were relatively small, whereas those obtained from only the potential analysis were large errors in all three conventionally used roll-damping ratios. In addition, the computational time consumed by the CMP model was longer than that consumed by the potential theory but faster than the full CFD simulation for all wave conditions. Subsequently, based on the motion analysis results, the seakeeping performance was evaluated in a real sea environment, and the results on the single significant amplitude (SSA) were discussed through comparison with the results of the potential analysis and experiment.