This is Publication No. 175 of the VBD, the Duisburg experimental establishment for inland-waterways shipbuilding. Ducted propellers would be used on more inland vessels but for the danger of timber and other material, floating or whirled up from the bottom of the waterway, being drawn into the duct and jamming or damaging the propeller. Sea-going ships are subject to a similar hazard from driftwood and ice. Methods of preventing the ingress of floatsam and other material be self-clearing ducts (see Abstract No. 30,320, Dec. 1970) and by fitting a secondary duct (see for example Abstract No. 31,329, Sept. 1971) have previously been studied, and the present investigation is a continuation of this work. The investigation was carried out in open-water tests with models at the VBD, and the results are described and discussed; a number of underwater photographs, in which nylon threads indicate the flow pattern, are included. Secondary ducts of various forms, mounted forward of the main duct so that an annular slot is left between the two ducts, were tested for the protection afforded, and the efficiencies of the complete duct systems were also measured. It was found that guide baffles, used as supports in the space between the two ducts, improved efficiency, particularly for going astern (they do not completely restore the losses due to the forward (secondary) duct obstructing the flow). The inflow through the forward duct effectively kept foreign bodies away from the inner wall of the main duct; there appeared to be no danger of their going through the slot and so entering the space between the blade tips and the duct wall (the most vulnerable region). Foreign bodies were able to leave the system through the main aperture during astern operation, without fouling the secondary duct. The effectiveness of the spiral groove as an addditional safety-measure during stopping or when going astern was confirmed (ducts with such grooves would be expensive to produce). Order from: BSRA as No. 47,135.

  • Availability:
  • Corporate Authors:

    Seehafen-Verlag Erik Blumenfeld

    Celsiusweg 15, Postfach 1347
    2000 Hamburg 50,   Germany 
  • Authors:
    • Luthra, G
  • Publication Date: 1977-6


  • German

Media Info

  • Features: References;
  • Pagination: 8 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00168344
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Feb 16 1978 12:00AM