The typical properties of a new stern shape provided with cochlea (helical) channels are displayed by comparing many model-test results. The test and design methods of the new stern shape are thoroughly explained. The manipulation of the wake by means of the channel system leads to the following results: 1. A reduction of the thrust pulsation of the single propeller blades. 2. A drastic reduction in amplitude of the main frequency of the blade thrust, leading to its complete elimination. 3. A shift to deeper sectors of the propeller disc of the reduced blade thrust maxima. 4. A counter-propeller effect generated by the vortex induced in the wake. 5. A limitation of the increase of towing resistance due to the wake vortex and a possible reduction below the resistance of the corresponding traditional ship. 6. A conveyance into the propeller disc of the (viscous) wake having lapped the surface of hulls provided with more than one propeller. The combined effect of these contributions to saving of propulsive power leads to a very substantial benefit. A power saving of the order of 25% was achieved on comparative self-propulsion tests performed with two twin-screw models as well as drastic reduction of propeller-induced hull vibrations. Similar benefits could be expected from the adoption of the cochlea channelled stern on any kind of ship, not only with twin-screw hulls. Order from: BSRA as No. 47,492.

  • Availability:
  • Corporate Authors:

    International Periodical Press

    193 Heemraadssingel
    Rotterdam,   Netherlands 
  • Authors:
    • Tommasi, G B
  • Publication Date: 1977-9

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Filing Info

  • Accession Number: 00170907
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Mar 29 1978 12:00AM