A Wind Tunnel Study on the Interaction of Hot Exhaust from the Funnel with the Superstructure of a Naval Ship

Prediction of temperature profile and trajectories of the ship exhaust plume from the funnel around the superstructure is not amenable to theoretical analysis and empirical calculation procedures. These predictions are of vital importance for Naval Architect from the initial phase of design for positioning and arranging of various superstructure electronics (radars, antenna), weapons and intakes (gas turbine, ventilation) in the superstructure and with the least interference with the hot exhaust flume from the funnel. However all Modern naval ships tend to favor short funnels and tall mast to house electronics. This makes them prone to the problem of smoke nuisance where hot exhaust gas gets entrapped into turbulent wake of the superstructure and deteriorates the performance of electronics, weapons, sensors, increase the ships infra red signature and hampers the internal ventilation and GT intakes. Experiments conducted in wind tunnel on the model ship superstructure are the only reliable tool that is available to estimate temperature field as well as to study the exhaust smoke superstructure interaction on ships. This paper presents the mapping of the temperature field around a simplified topside configuration of a generic frigate. The configuration comprises of two funnels (forward and aft) a superstructure block consisting of bridge, mast and two intakes (fwd and aft) ahead of respective funnels along with piping network with blowers to achieve the desired air flow through funnels and intakes. A set of electrical heaters has been fitted in the funnel inlet pipe to provide hot gases. The exhaust temperature from the funnel has been maintained at 50degC above the ambient temperature through out the experiment. The mapping of temperature profile was conducted by measuring temperature using RTD. Six measurement planes were chosen so as to cover the most critical region around the superstructure with a total of 1344 discreet measurements. The study provides an understanding of the near field behavior of hot flumes and also suggests possible location of intakes and regions of hot spots in the superstructure. These results can serve as reference data for Naval Architects for their use in the validation of the numerical simulation using CFD.