Some Aspects of Submarine Design: Hydrodynamics

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Some Aspects of Submarine Design Part 1. Hydrodynamics
Prof. P.N.Joubert
Under Contract to Maritime Platforms Division Platforms Sciences Laboratory DSTO-TR-1622 ABSTRACT The history of submarines shows there were two significant advances in the performance of submarines, which occurred after full scientific studies were undertaken. The first was by the Germans at the end of World War II when they produced the Type 21, which could have upset the balance in the U-Boat campaign if it had arrived earlier. The second was by the US Navy with Albacore which had a submerged speed of over 30 knots. To neglect full scientific studies would be a serious mistake in the design of any future replacement submarine. Design is shown to be like a jigsaw puzzle where altering one piece requires alterations in all surrounding features to make a workable complete design. The basis of improved hydrodynamic features is discussed. A new nose shape is presented which should improve the performance of the forward passive sonar up to operational speeds. Other major sources of resistance may be improved. It is proposed a first major step should be to establish the detailed performance of Collins using wind tunnels and computational fluid dynamics which will serve as the comparative foundation for any new design. RELEASE LIMITATION Approved for public release

Published by DSTO Platforms Sciences Laboratory 506 Lorimer St Fishermans Bend, Victoria 3207 Australia Telephone: (03) 9626 7000 Fax: (03) 9626 7999 © Commonwealth of Australia 2004 AR-013-204 October 2004

APPROVED FOR PUBLIC RELEASE

Some Aspects of Submarine Design Part 1. Hydrodynamics

Executive Summary
The history of submarines subsequent to the first truly operational vessel, Holland, launched in 1899, showed two significant advances as opposed to steady incremental developments. These resulted from full scientific studies of all the problems. The first of these advances was made by the Germans at the end of World War II, when they produced the Type 21 which had major improvements in range and battery time while their underwater speed increased to 18 knots compared to 5 knots on previous vessels. Design diving depth was increased dramatically. They could operate below the Allies submarine defence weapon systems. The second advance was made by US designers who produced Albacore in 1953 with a shape suited to full underwater operation. Its length-tobeam ratio was only 7.7 and top underwater speed was 33 knots. The drag coefficient was only 0.1 compared to 0.35 on previous submersible designs. It is clear that scientific studies should be a starting point for any future submarine design. A review of the literature covers priorities in design and shows how enhancement of one feature interacts with other features and may even result in an overall loss of performance despite the perceived advantage of the enhanced feature. Hydrodynamic aspects are then discussed starting with the shape and reasons why a length-to-beam ratio of about 7.5 gives the minimum resistance. All features affecting the resistance are discussed including the boundary layer, laminar flow, transition, turbulence and separation and how the flow over the principle passive sonar should be as quiet and smooth as possible. Added resistance from sails, masts, snorkels and appendages need careful streamlining and attention in design. A proposed profile of a new submarine is presented which has the passive sonar far forward in the streamlined nose with the torpedo tubes positioned further aft. It should be a quieter vessel with more effective sonars. The profile requires shortening to reduce the displacement and then the internals need rearranging. The design process then begins, which is iterative. In order to proceed with such concepts it is vital to have a database. Our current submarine, the Collins class, should be the base from which all changes and proposals are measured. It is suggested detailed wind tunnel...
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