Modelling     Measurement     Past projects


General information

SlenderFlow software uses slender-body theory to calculate the flow of water around ships. It is developed by Dr Tim Gourlay at Perth Hydro, and used for our ship hydrodynamics consulting. As a potential-flow code, it is very numerically efficient, with computation times typically a fraction of a second.


  • Hull shape (exact offsets, or use a modified standard hull)
  • Ship speed
  • Channel type
  • Channel dimensions


  • Squat and dynamic draft at bow, midships and stern
  • Hydrodynamic pressure around ship and on seabed
  • Drawdown on canal banks

Commercial track record

The methods in SlenderFlow have been successfully used in many commercial projects, including:

  • Development of UKC guidelines for Membrane LNG carriers, Moss LNG carriers and Condensate carriers, for Barrow Island (Gorgon) LNG Terminal
  • Development of UKC guidelines for Port Ashburton (Wheatstone) LNG Terminal
  • Comparison with full-scale trials results and development of UKC management method for Port of Hong Kong

Model-scale validation

SlenderFlow methods have been validated against a wide range of model tests from the European shallow-water towing tanks at Flanders Hydraulics, DST Duisburg and BAW Hamburg. The international "PreSquat" blind validation workshop of 2013 showed that SlenderFlow methods produced consistently accurate squat predictions.

Full-scale validation

Full-scale ship motion trials have now been undertaken on 60 cargo ship transits through shallow channels in Hong Kong, Torres Strait, Geraldton and Fremantle. The results have been used to validate and refine SlenderFlow for application in shallow shipping channels.

Ship types

SlenderFlow may be used for any displacement (non-planing) vessel, including ocean-going commercial and military vessels, European inland vessels, catamaran ferries and trimaran ferries.

Bathymetry types

  • Shallow open water
  • Dredged channels
  • Canals (Panama, Suez)
  • European inland waterways

Method options

  • Open-water constant depth (Tuck 1966)
  • Dredged channel (Beck, Newman & Tuck 1975)
  • Arbitrary cross-section canal (Gourlay 2008)
  • Nonlinear narrow canal (Gourlay 2000)
  • Trans-critical monohull (Gourlay & Tuck 2001)
  • Trans-critical catamaran or trimaran (Gourlay 2008)

© 2017 Perth Hydro Pty Ltd.