It is possible to observe a ground vortex emanating from a runway rising and disappearing into the engine inlet when the engine revolutions are increased just before a plane taxies. Whether the vortex is visible depends on the conditions on the day, air temperature humidity and pressure, as it is the high-speed low- pressure core of the vortex that causes the moisture in the air to condense, making it visible. A similar phenomena occurs in water where the vortices are known as propeller hull/vortices (PHVs) when they are caused by propellers or thrusters. In 1992 an observation was made that advanced knowledge of the phenomenon and emphasised the need for a better understanding of it. The observation was made during a model test in a cavitation tunnel, carried out on the model of a dynamically positioned stable platform to try and establish what was causing the cracked hull plating and structure in the vicinity of the twin propellers when they operated at full power. Some of the findings from the model tests are provided in the article by a group of high-speed flash photographs with the propeller at different polar angles, showing the cavitating core of the hull vortex(es) (HV), that were present. The interpretation given for the view of the back of the blade, which is the only one usually published, without clear pictures of what is occurring on the blade face, is that the HV ends on the blade. It is now obvious that this is an incorrect interpretation. The cavitating core of the HV is a manifestation of the swirling flow induced by the propeller in its interaction with the flow from the hull upstream. When a cavitating core is not visible it does not follow that the HV is not present, but simply that the conditions at the core do not produce cavitation. Thus it may be concluded that the ubiquity of non-cavitating HVs is likely to be high because of the plentiful source of vorticity when pusher screws are used.

  • Supplemental Notes:
    • Naval Architect, March 1995, p E150 [2 p, 1 ref, 6 fig]
  • Authors:
    • English, J W
  • Publication Date: 1995


  • English

Subject/Index Terms

Filing Info

  • Accession Number: 00710694
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Aug 14 1995 12:00AM