Development and Model Tests of a Surface Ship Additive System

A Froude scaled ship model 11.4 feet long and 1.4 feet girth was tested for drag while dilute polymer (FRA) water solutions were ejected around the hull. A ram scoop-slot ejective arrangement in conjunction with a polymer mixing and feed system was developed and utilized successfully to affect the model's drag. Four series of tests were conducted at various operating conditions including three ejection slot gap settings and two ejective slot locations. An actual drag reduction of about 12 percent of the total drag at top speed (20 ft/sec), was obtained. Drag reduction of over 18 percent of the total drag or more than 55 percent in the frictional drag is conceivable at proper ejection conditions with two ejection stations. This may be obtained when the ejected flow amounts only to about ten times the sublayer flow rate and contains a polymer concentration between 1000 and 1300 ppm. Additional studies are recommended to enable the optimization of the polymer ejective system and assess its full potential. (Author)