Experimental and CFD analysis: Effects of bottom appendages on the slamming characteristics of rigid hull structures during water entry

The ship slamming phenomenon is a pivotal issue in the field of navigation. Through a combination of numerical and experimental methods, this paper analyzes the impact hydrodynamic performance of two rigid hull structures, one with and one without bulbous bows. Drop tests were conducted on large-scale hull models from heights ranging from 250 mm to 700 mm. More detailed characteristics of the free-surface evolution and pressure distribution were obtained via computational fluid dynamics (CFD) techniques. Combining experimental observations with numerical simulation results, the specific effects of bottom appendages on hydrodynamic properties were thoroughly discussed. The study revealed that the presence of appendages significantly promotes early fluid separation, subsequently slowing fluid velocity. Conversely, models without appendages favor fluid accumulation effects. These differences profoundly affect the evolution path of flow patterns and the pressure distribution. Notably, in configurations with appendages, the local pressure peak at the jet impact location even exceeds the pressure load in the pile-up water region, demonstrating extremely high localized pressure concentration. Even when adhering to more conservative design standards, the magnitude of this jet impact load remains unusually high, posing a significant threat to the safe design of ship structures and warranting attention.