HYDRODYNAMIC DESIGN OF MERCHANT SHIPS FOR HIGH SPEED OPERATION

This paper discusses some of the hydrodynamic features of medium size and large merchant ships intended to operate at speeds higher than those of today. The ships considered are bulk carriers, tankers, cargo liners and passenger vessels from about 400 ft to 1,000 ft in length with service speeds from just below 20 knots to above 30 knots and which may have propelling powers up to about 100,000 H.P. on one or two shafts. Power requirements in calm water are considered and criteria in the form of a boundary speed and hydrodynamic efficiency factors are introduced. These criteria are applied to fine form cargo liners and large, full form tankers and bulk carriers at relatively high speeds. Some effects on propulsive efficiency of varying propeller diameter and rate of rotation are examined, and the possible advantages of contra-rotating and ducted propellers are discussed. Some of the factors which affect the performance of high speed ships in waves and their maneuverability and steering qualities are then described. These include freeboard requirements and the influence of ship length and speed on pitch and heave motions in specified sea conditions. The effects of bulbous and ram bows on resistance in calm water and on seakeeping behaviour are also discussed. Finally, possible future developments of unorthodox high speed merchant ships are briefly considered. These include ships for super-critical operation, submarine tankers and cargo ships, and very high speed displacement ships.