Characteristics of Horseshoe Vortex in Developing Scour Holes at Piers

The outcome of an experimental study on the turbulent horseshoe vortex flow within the developing (intermediate stages and equilibrium) scour holes at cylindrical piers measured by an acoustic Doppler velocimeter (ADV) is presented. Since the main aim was to analyze evolution of the turbulent flow characteristics of a horseshoe vortex within a developing scour hole, the flow zone downstream of the pier was beyond the scope of the investigation. Experiments were carried out for the approaching flow having undisturbed flow depth (=0.25 m) greater than twice the pier diameter and the depth-averaged approaching flow velocity (=0.357 m/s) about 95% of the critical velocity of the uniform bed sand that had a median diameter of 0.81 mm. The flow measurements by the ADV were taken within the intermediate (with depths of 0.25, 0.5, 0.75 times the equilibrium scour depth) and equilibrium scour holes (frozen by spraying glue) at a circular pier of diameter 0.12 m. In order to have a comparative study, ADV measurements within an equilibrium scour hole at a square pier (side facing the approaching flow) of sides equaling the diameter of the circular pier were also taken. The contours of the time-averaged velocities, turbulence intensities, and Reynolds stresses at different azimuthal planes (0, 45, 90°) are presented. Vector plots of the flow field at azimuthal planes reveal evolution of the characteristics of the horseshoe vortex flow associated with a downflow from intermediate stages to equilibrium condition of scour holes. Bed-shear stresses are determined from Reynolds stress distributions. Flow characteristics of the horseshoe vortex are discussed from the point of view of similarity with velocity and turbulence characteristic scales. An imperative observation is that flow/turbulence intensities in the horseshoe vortex flow in a developing scour hole are reasonably similar.

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  • Supplemental Notes:
    • Abstract reprinted with permission from ASCE
  • Authors:
    • Dey, Subhasish
    • Raikar, Rajkumar V
  • Publication Date: 2007-4

Language

  • English

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Filing Info

  • Accession Number: 01046654
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 19 2007 3:06PM