The effect of duct cross-section on the reduction of noise produced by marine propellers using numerical and laboratory methods
Ship noise emission has many environmental impacts and its reduction can reduce or eliminate some of these harmful effects. Hence, recognizing noise-generating source and investigating noise reduction techniques is the first step in eliminating these harmful effects. Studies show that ship propeller is one of the main commercial ship noise-generating sources. The duct placement around the propeller is one of the well-known solutions for reduction noise eliminated from marine propeller. In this paper, we first investigate mathematical equations of noise emission in far field. In the following, a basic geometry was introduced for ducted propeller and necessary numerical calculations were done to estimate SPL at a certain distance from the propeller (by using FWH equations). The measured SPL emitted from the propeller in CFD approach (solving the FWH) shows 28% reduction for ducted propeller in comparison with the propeller without the duct. In experimental approach (after removing the ambient noise) shows 37% reduction for ducted propeller in comparison with the propeller without the duct.
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