Slam-induced loads on a three-dimensional stern model entering into water considering the bottom propeller shaft

Abstract

The slamming load characteristics of stern structures under severe sea conditions are a research topic that deserves special attention. However, owing to the complex geometric characteristics of the stern, the current understanding of its slamming load characteristics is still insufficient. This study uses the computational fluid dynamics (CFD) method to conduct a numerical simulation study on the water impact problem of the stern structure of a container ship. Unlike previous studies, this calculation specifically considers the influence of the actual propeller shaft on the slamming process. The numerical calculation results were first compared with the existing experimental data for impact load verification, with errors within 10 %. Through numerical simulation, the details of the three-dimensional (3D) free surface flow that was difficult to observe in the experiment were successfully reproduced, and the flow separation and air bubble entrapment phenomena induced by the bottom propeller shaft were captured for the first time. The pressure distribution and slamming force characteristics of the stern surface for falling heights ranging from 250 mm to 900 mm were systematically analyzed, and the impact load‒time history curves of typical measurement points were discussed in detail. The findings reveal that fluid disturbances caused by the bottom propeller shaft weaken the correlation between the impact pressure and initial deadrise angle. Finally, the influences of parameters such as the impact velocity, model scale, shaft size, and model dimensions on the load characteristics were explored. These conclusions can help to improve our understanding of the slamming load characteristics of stern structures.