Abstract

The coupled interaction between the damaged ship motion and flooding water is very complicated. This paper studies two kinds of cabins with free surface. CFD software STAR−CCM+ is carried out to numerically simulate intact cabin resonant sloshing and damaged cabin flooding. The VOF method is used to capture the fluid interface. The overset mesh techniques is employed to handle the mesh update following transient cabin motions. The numerical results are satisfactory in comparison with experimental results.

INTRODUCTION

When a ship is damaged, water floods into the damaged cabin and subsequently flows to other cabins through the internal openings. The performance of a damaged ship is influenced not only by external water, but also by the internal loads of the fluid flow and sloshing. For intact cabin, the water inside is not communicated with the water outside and resonant sloshing occurs when the external excitation frequency is close to the natural frequency of the liquid sloshing. For damaged cabin, the water inside is communicated with water outside and transient flooding occurs, resulting in liquid sloshing and changes in parameters such as mass and buoyancy. In turn, the sloshing of the water in the cabin and the change of parameters will affect the motion of ship. Therefore, the coupled interaction between the damaged ship motion and flooding water is very complicated.

Potential flow methods are the common numerical approach to study the complex hydrodynamics problem. In previous studies, the classical hydraulic model is widely used to calculate the floodwater dynamics. Further, the lumped mass method and the shallow water equation are developed. Ruponen (2007) used a hydraulic model based on Bernoulli equation to calculate the flow rate, and considered the flooding development process according to the hydrostatic pressure of the flooding cabin. Santos and Soares (2008) used the shallow water theory to investigate the effects on roll motion of water inside the compartments below the main vehicle deck of a passenger Ro–Ro ship and the shape of the free surface inside the flooded compartment and possible phase shifts in the water motion in relation to the roll motion. Acanfora (2019) developed and presented a fast simulation method, based on the lumped mass approach. The lumped mass path in space depends on free–surface inclinations that differ from the ship angles of the roll and pitch. However, in the case when the ship undergoes large amplitudes of motion, these approaches cannot accurately capture the viscous features of floodwater and sloshing and lack the ability to model the violent flows with non–linear free surface.

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