Interference Between a Hull and a Sternmounted Ducted Propeller

摘要

The hydrodynamic interference between an underwater hull and a stern-mounted ducted propeller is predicted by theoretical analysis. The analysis assumes axially symmetric potential flow, and the hull wake vorticity is concentrated into multiple vortex cylinders extending downstream from the boattail. The interference forces are predicted versus the following geometric parameters with the hull shape held fixed to represent TMB Model 4620: duct chord-to-diameter ratio, duct size, duct axial spacing from hull, axial location of propeller within duct, duct camberline shape, and number of vortex cylinders used to represent hull wake. Also, the effect of duct profile thickness upon the analytical results is estimated and shown to be small. The computed results show that cylindrical ducts are unsuitable for propulsion of the assumed hull shape because, at cruising speed, they are ineffective in reducing the propeller thrust, they have large leading-edge suction, and they produce large hull interference. However, when duct camber is added, the results also show that if all of the other geometric parameters are specified, a duct camberline can be designed so that the duct carries more thrust than the propeller without any leading-edge suction or hull interference. (Author)