VISUALISATION OF THE SURFACE FLOW PATTERN ON A VEHICLE-LIKE BLUFF BODY

The purpose of these experiments was to investigate the surface flow pattern on a vehicle-like body. The experiments were carried out at very low Reynolds numbers, between 2400 and 100000, based on the length of the model. The flow field was studied with two different boundary conditions, known as stationary and moving ground. In the case with stationary ground, the model was placed at various distances from the leading edge of the ground plate to determine how the growing boundary layer on the plate and the changes in potential flow influenced the surface flow over the model. Two different visualisation techniques were used to determine the flow. Dye line visualisation in water gave a picture of the flow both on the surface and, when separation occurred, of the flow field close to the body. An oil particle mixture was used on the model surface in wind tunnel experiments, to determine the flow structure close to and downstream of the lines of separation on the surface. The visualisation showed a more complex flow field than reported in earlier investigations. Owl-face separation patterns were found on the roof and on the slanted back. The owl-face pattern is an indication of two vortices leaving the surface. Lines of attachment on the slanted back indicated the presence of two strong longitudinal vortices. On the side surface, an A-pillar vortex and a vortex at the edge between the bottom and the side were observed. On the vertical rear part of the model, indications of a bending, horse-shoe like, vortex was found. A comparison between the results from the stationary ground and the moving ground experiments showed that it is possible to obtain similiar flow patterns with the two types of boundaries. For the same velocity, the model had to be placed in a certain position on the stationary ground plate to give a similar surface flow pattern as that with moving ground. When the velocity is increased, this position of the model on the ground plate is moved further away from the leading edge.

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• Corporate Authors:

  Chalmers University of Technology, Sweden

  Department of Applied Mechanics/CHARMEC
  Gothenburg,   Sweden 
• Authors:
  • Landby, P
• Publication Date: 1989

Language

• English

Media Info

• Pagination: 38 p.
• Serial:
  • Publication of: CHALMERS TEKNISKA HOEGSKOLA
  • Publisher: Chalmers University of Technology, Sweden
  • ISSN: 0346-718X

Subject/Index Terms

• TRT Terms: Aerodynamics; Automobiles; Dyes; Equipment; Oils; Scale models; Speed; Structural models; Tests; Water; Weighing devices; Wind
• Uncontrolled Terms: Scale
• ITRD Terms: 5492: Aerodynamics; 1243: Car; 6784: Colour; 3674: Equipment; 6205: Model (not math); 4961: Oil; 6204: Scale; 5408: Speed; 6255: Test; 4355: Water; 2554: Wind
• Subject Areas: Bridges and other structures;

Filing Info

• Accession Number: 00605806
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• Report/Paper Numbers: 1989:4
• Files: ITRD, TRIS
• Created Date: Mar 31 1991 12:00AM