Flow Visualization Studies of Exhaust Smoke-Superstructure Interaction on Naval Ships

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The problem of ship funnel exhaust is often studied through flow visualisation using smoke in a wind tunnel. It is a very useful tool for the naval architect to ensure that the funnel exhaust will not interfere during operation. Naval ships are particularly prone to the problem of smoke nuisance because they tend to favor short funnel heights because of competition for topside space. This paper presents the flow visualization studies undertaken to understand the interaction between a bluff body air wake (of the funnel and superstructure/mast) and the ship's exhaust on naval ships. As a first step, the analysis of the exhaust smoke-superstructure interaction was carried out in a wind tunnel for a generic frigate shape. Four variants of the superstructure configuration with progressive introduction of the structures on the topside (i.e. the superstructure/mast upstream and downstream of the funnel) were investigated in the wind tunnel at two velocity ratios through flow visualization studies to understand their effect on the exhaust plume path. Apart from providing an insight into the process of plume dispersion in the vicinity of the funnel and other structures on topside of naval ships, the results of the flow visualization studies presented can also be used for validation of the computational fluid dynamics (CFD) simulations (including particle tracing) of the exhaust smoke-superstructure interaction for cruise vessels, ferries, yachts, as well as naval ships.