Paper On Water jet Propulsion Discussed During SNAME Philadelphia Section Meeting
The subject of the January meeting of the Philadelphia Section of The Society of Naval Architects and Marine Engineers was "Waterjet Propulsion." Considering the U.S. Navy's latest philosophy of smaller, faster, ships, the paper was very timely.
Lt. Comdr. Dennis F. Kruse, USN, presented his paper titled "Waterjet Propulsion, An Optimization Procedure." The paper is a description of the development of computer programs for optimization and performance evaluation of certain waterjet propulsion design parameters. Work was performed as a graduate student research project at M.I.T. and was sponsored by the U.S. Navy for purposes of furthering its hydrofoil boat program. The presentation included the basic dynamics of waterjet propulsion and the rationale involved in the optimization process and performance evaluation.
An existing computerized method for optimum design of waterjet propulsion systems for sub-cavitating hydrofoil craft is analyzed for sensitivity to variations in normally fixed parameters and for sensitivity to variations in the starting points for the search used in the optimization procedure. A compatible method for off design evaluation of waterjet propulsion systems is developed and incorporated into the optimization program in a manner which permits off design evaluation to be performed separately or in conjunction with design. The evaluation routine requires that system geometry, craft characteristics and pump characteristics be specified. System drag and losses are calculated to determine required flow rate and pump head and the corresponding pump speed, efficiency and required power are determined. Results of design optimization for a series of similar craft are presented and show a strong sensitivity to the input estimate of the take-off drag. Sensitivity to starting values of the independent variables was noted in some cases and appears to be due to the fact that jet velocity ratio dominates the other independent variables as an influence on total system weight.
John Lawlor, Sun Shipbuilding & Dry Dock Company, coordinated the meeting for the local Section.
Discussers included K.C. Thornton, J.J. Henry Company; F. Collison, Sun Shipbuilding and Dry Dock Company, and S.S. Morse, Arco.