Hydrodynamic Efficiency Improvements for U.S. Navy Ships

Abstract

ABSTRACTThis paper reports on an investigation of the applicability of recent hull efficiency improvement concepts to U.S. Navy ships. Among the concepts investigated were stern flaps, Grim Wheels, alternate aftbody configurations, bulbous bows, and flow modifying ducts. Extensive model testing was conducted at the David Taylor Research Center (DTRC) for each concept, and care was taken to check out critical propeller cavitation and noise aspects associated with the investigation of alternate stern configurations and Grim Wheel concepts. A guiding principle in this program was to utilize the expertise available both here and abroad so that each design concept would have the greatest chance of success.As a result of these investigations, significant gains in fuel economy were obtained. Specifically, full scale trials of FFG‐25 (USS Copeland), equipped with and without a stern flap, demonstrated that fuel savings of 5–9% are achieved at speeds above 12 knots. In addition, fuel savings of 9.4% for T‐AGS 39 equipped with a Grim Wheel and 5.6% for the combination of a large bulbous bow and a large diameter/ low RPM propeller on AE‐36 have been predicted. The paper concludes with a direction for future applications to U.S. Navy, and other ships.