| Abstract | Freeing ports on fishing vessels are a significant safety feature. They are designed to reduce the build up of green water on deck that may lead to loss of stability. At a more mundane level they reduce wetness on decks that are the working platforms for the fishers. Wet decks that are moving working platforms are clearly a hazard. The present study deals more with the build up of water on deck rather than just general deck wetness. It attempts to quantify the amount of water on deck for different freeing port configurations, using parameters such as number of freeing ports, freeing port areas, deck area etc. The study uses numerical simulations to evaluate these parameters. One particular vessel has been used throughout the study, namely a typical fibreglass 65 foot fishing vessel of recent design. The main conclusions of the study are that generally there is not a great deal of difference between the amounts of water on deck for the different freeing port configurations. Although larger freeing ports allow more water on deck if the ingress and egress of water flowing through the freeing ports is unhindered in both directions, for freeing ports fitted with some device (such as ‘flaps’) that hinders the in-flow but not the out-flow then having larger freeing ports is shown to be beneficial. The benefits here are more to do with stability than general deck wetness. It is in fact clear from some of the results that larger freeing ports lead to wetter decks. The motions of the vessel in the study with water on deck have been evaluated and it is shown that different freeing port configurations can lead to different motions of the vessel, particularly in the early stages of flooding. |
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