Experimentally Observed Features of the Turbulent Near-Wake of a Model Ship
Abstract
Flow visualization techniques are used to study the turbulent wake of a model ship, with and without propulsion, for distances up to two ship-lengths aft. The turbulent wake is characterized by a thin, rapidly spreading, surface- current layer and a central vertical region of turbulent fluid, resulting in a tee shape for the near wake. The turbulent surface layer spreads more rapidly in the propelled case than in the non-propelled case. The only large-scale coherent vortices observed in the subsurface wake were a pair of inboard rotating turbulent vortices produced in the stem cavities on either side of the rudder. These vortices diffuse quickly and do not appear to affect the free surface. For distances less than two ship lengths aft, there is a region of unsteady, irregular free-surface disturbances which corresponds to the subsurface region of turbulent flow. At the edges of this turbulent region, the small scale disturbances created by the turbulence coalesce into relatively organized, but unsteady, waves which are independent of the Kelvin wave pattern. These organized waves propagate outward into the irrotational free stream, and may be related to surface ship wake signatures obtained via synthetic aperture radar techniques.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1992
- Accession Number
- ADA251150
Entities
People
- David T. Walker
- Vincent G. Johnson
Organizations
- University of Michigan