Hostname: page-component-586b7cd67f-t7fkt Total loading time: 0 Render date: 2024-11-25T01:35:30.022Z Has data issue: false hasContentIssue false
  • English
  • Français

Effect of Base Slant on Flow in the Near Wake of an Axisymmetric Cylinder

Published online by Cambridge University Press:  07 June 2016

Thomas Morel
Thomas Morel*
Affiliation:
Fluid Dynamics Department, General Motors Research Laboratories, Warren, Michigan
Get access

Summary

The effects of slanting the base of a slender axisymmetric cylinder (length/diameter ratio of 9), aligned with the flow, was studied experimentally. The body was equipped with interchangeable rear ends covering a range of slant angles between 0° (vertical) and 70°. It was found that the base slant has a very dramatic effect on body drag, particularly in a relatively narrow range of slant angles where the drag coefficient exhibits a large local maximum (over-shoot). Detailed study of the flow showed that the drag overshoot is related to the existence of two very different Separation patterns on the slanted base. One pattern is similar to that found behind axisymmetric bodies with no base slant, and its main feature is the presence of a closed Separation region adjacent to the base. The other pattern is highly three-dimensional with two streamwise vortices forming along the sides of the slanted base. This pattern sets in very abruptly at a “critical” slant angle α ∼ 47°. Drag force measurements showed that, at first, the drag coefficient slowly increases with the slant angle, but then jumps suddenly upwards to more than double its baseline value (from CD = 0.24 to CD = 0.625) at the critical angle. At angles higher than that CD decreases again, and at 70° it is about equal to the baseline value. Further effects of the slant angle are the generation of a large side force and a significant increase in near-wake flow periodicity.

Type
Research Article
Information
Aeronautical Quarterly , Volume 31 , Issue 2 , May 1980 , pp. 132 - 147
Copyright
Copyright © Royal Aeronautical Society. 1980

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1 Calvert, J.R., Experiments on the Flow Past an Inclined Disk. Journal of Fluid Mechanics, Vol. 29, pp 691–703, 1967 Google Scholar
2 Eiffel, G., The Resistance of the Air and Aviation. Houghton, Mifflin and Co., Boston, pp 39–45, 1913 Google Scholar
3 Janssen, L.J. and Hucho, W.H., Aerodynamische Formoptimierung der Typen VW Golf and VW Scirocco. In the Proceedings of Kolloquium ueber Industrieaerodynamik, Part 3, pp 49–70, 1974 Google Scholar
4 Morel, T., The Effect of Base Slant on the Flow Pattern and Drag of 3-D Bodies with Blunt Ends. Aerodynamic Drag Mechanisms, Editors G., Sovran, T., Morel and W.T., Mason, Plenum Press, pp 191–217, 1978 Google Scholar
5 Roshko, A., On the Drag and Shedding Frequency of Two-Dimensional Bluff Bodies. MCA TN-3169, July 1954.Google Scholar