BOW AND STERN SINKAGES CAUSED BY INTERACTION BETWEEN PASSING SHIPS

As the first of a series of studies by the National Maritime Institute, Middlesex, England, on port approach problems, this report describes experiments on the interactive effects of two ships passing each other in a channel. Models of a tanker and general cargo liner were tested by NMI with one ship overtaking another, and with them passing in opposite directions. It was found the hydrodynamic pressure changes at the bow and stern of each vessel interacted causing significant vertical motions (larger at the stern and thus requiring a greater depth below the ships' keels. The experimental runs covered different depths, draughts, speeds, and encounter speeds; tables were drawn up as a guide to port authorities to enable them to obtain optimum economic and safety conditions in their respective ports by, where necessary, modifying channel depths and widths, and limiting vessels' speeds. In general the additional sinkages at bow and stern of a ship could be kept small if: (i) separation between vessels is large, (ii) under keel clearance is large, (iii) vessels' speeds are kept low. The tables in the appendix give speed/depth factors, and bow/stern sinkage as a fraction of ship length, relative to speed ratio. Thus specific guidelines can be drawn up for certain ship sizes. The National Ports Council has commissioned four other studies within the general title, "Ship Behaviour in Ports and Their Approaches"--these will cover the effects of confined and shallow waters on ships' steering characteristics; ship squat in confined waters; vertical motions of vessels exposed to a swell in shallow water; and the hydrodynamic "virtual mass" of water which moves sideways with a ship as it berths. From these studies the Council expects to benefit in planning port approaches, and will be able to make them safer and cheaper to operate.

• Corporate Authors:

  National Ports Council

  Commonwealth House, 1-19 New Oxford Street
  London WC1A 1DZ,   England 
• Publication Date: 0

Media Info

• Pagination: n.p.

Subject/Index Terms

• TRT Terms: Channels (Waterways); Maneuvering; Speed control; Thinness; Traffic speed; Vessel traffic control; Water traffic
• Uncontrolled Terms: Sinkage; Speed reduction
• Old TRIS Terms: Channel traffic management; Model testing; Narrow channel navigation; Restricted water operation; Shallow water maneuvering; Slender bodies
• Subject Areas: Marine Transportation; Operations and Traffic Management; Terminals and Facilities; Vehicles and Equipment;

Filing Info

• Accession Number: 00312210
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 26 1980 12:00AM