The U.S. Navy has been interested in podded propulsion for over 20 years and has conducted model experiments on several designs in order to define their powering performance and other hydrodynamic characteristics. The model test drag data on several of these designs are analyzed and presented in terms of drag coefficient and pod residuary resistance. The model powering tests form a data base for estimating thrust deduction and wake fraction.
Podded propulsion frees the designer from the constraints imposed by the traditional propeller support arrangements to offer advantages with regard to better hull design for lower resistance, improved propeller inflow, and more efficient propellers. Compared to the traditional design, some podded designs are predicted to reduce the delivered power at the propeller by as much as 20%. The design objectives, design constraints and reasons for improved performance are discussed for each of the podded designs that are presented.
