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Experiments in Fluids

, Volume 28, Issue 6, pp 559–575 | Cite as

Motion of a cylinder adjacent to a free-surface: flow patterns and loading

  • Q. Zhu
  • J. -C. Lin
  • M. F. Unal
  • D. Rockwell

Abstract

The flow structure and loading due to combined translatory and sinusoidal motion of a cylinder adjacent to a free-surface are characterized using a cinema technique of high-image-density particle image velocimetry and simultaneous force measurements. The instantaneous patterns of vorticity and streamline topology are interpreted as a function of degree of submergence beneath the free-surface. The relative magnitudes of the peak vorticity and the circulation of vortices formed from the upper and lower surfaces of the cylinder, as well as vortex formation from the free-surface, are remarkably affected by the nominal submergence. The corresponding streamline topology, interpreted in terms of foci, saddle points, and multiple separation and reattachment points also exhibit substantial changes with submergence. All of these features affect the instantaneous loading of the cylinder. Calculation of instantaneous moments of vorticity and the incremental changes in these moments during the cylinder motion allow identification of those vortices that contribute most substantially to the instantaneous lift and drag. Furthermore, the calculated moments are in general accord with the time integrals of the measured lift and drag acting on the cylinder for sufficiently large submergence.

Keywords

Vortex Vorticity Particle Image Velocimetry Velocimetry Vortex Formation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Q. Zhu
    • 1
  • J. -C. Lin
    • 1
  • M. F. Unal
    • 1
  • D. Rockwell
  1. 1.Department of Mechanical Engineering and Mechanics 354 Packard Laboratory, 19 Memorial Drive West Lehigh University Bethlehem, PA 18015

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