SCALE EFFECT ON STERN SEPARATION AND RESISTANCE OF A FULL HULL FORM

Limited regions of flow separation may occur at the stern of full-form hulls in model tests, and theoretical analysis suggests that the extent of this separation will decrease as the hydrodynamic scale is increased. In such circumstances, the validity of the usual method of predicting the viscous component of resistance of the full-scale ship from model results (by assuming that total viscous resistance varies with Rn in a constant ratio 1 + k (where k is the "form factor") to the frictional resistance of a flat plate) may be questioned. The Author (of the National Maritime Institute) gives an account of experiments carried out to ascertain how much this viscous extrapolation method is likely to be in error for a full-form ship. The investigation, made with double models in a compressed-air wind-tunnel, was based on a comparison between the results from a full form (a tanker parent-form) and a finer form (similar to the parent form but with an elongated stern) tested in identical conditions. Information from tests on corresponding floating models, at the lower end of the Rn scale, was also available. The experimental techniques are described, and the results are examined, in some detail. The findings appear to confirm that where a hull form is liable to more extensive stern separation at low Reynolds numbers than at high ones, the resistance will not be in a constant ratio to that of a form less subject to stern separation. The findings, and their limitations, are further discussed, together with some comments on these experimental techniques.

  • Availability:
  • Corporate Authors:

    Royal Institution of Naval Architects

    10 Upper Belgrave Street
    ,   United States 
  • Authors:
    • Gadd, G E
  • Publication Date: 1977-11

Media Info

  • Features: References;
  • Pagination: 13 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00177271
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Jul 19 1978 12:00AM