Evaluation of Large Diameter Propellers in Tunnel Stern Merchant Ships

摘要

As part of a broad program to seek hydrodynamic related improvements to effect energy savings in future U.S. Flag merchant ships, an evaluation of the potential of large diameter propellers in tunnel sterns was pursued. This embraced paper studies to relate potential improvement to ship type, size, and power, etc., and to develop design guidance. This was followed by model testing of two alternate afterbodies to an existing high-powered MARAD-developed containership. Experiments included propulsion and flow visualization for both designs and a wake survey for one. The results of the resistance and propulsion tests showed 4 and 8% reductions in delivered power at design speed over the parent single screw hull, for the two alternates, with 6 and 10% reductions relative to the conventional twin screw parent. Powering performance as well as goodness of flow favored a bulbous stern model over exposed shaft and strut configuration. The wake survey made for the bulbous stern model showed marked and potentially favorable changes from the conventional single screw parent.