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Non-Intrusive Underwater Measurement of Local Scour Around a Bridge Pier
Open AccessArticle

Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China
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Author to whom correspondence should be addressed.
Water 2019, 11(10), 2079; https://doi.org/10.3390/w11102079
Received: 9 August 2019 / Revised: 27 September 2019 / Accepted: 1 October 2019 / Published: 5 October 2019
(This article belongs to the Special Issue Bridge Hydraulics: Current State of the Knowledge and Perspectives)
A turbulent horseshoe vortex (HV) system around a wall-mounted cylinder in open channel is characterized by random variations in vortex features and an abundance of vortex interactions. The turbulent HV system is responsible for initiating the local scour process in front of the cylinder. The evolution of the turbulent HV system is investigated statistically and quantitatively with time-resolved particle image velocimetry. The cylinder Reynolds numbers of the flow are 8600, 10,200, and 13,600, respectively. A novel vortex tracking method was proposed to obtain the variations in position, size, and strength of the primary HV (PHV) which dominates the system most of the time. Relationships between the various features of the PHV during its evolutionary process were obtained through correlation analyses. Results show that the dimensionless mean lifespan of the PHV is about 5.0. Statistically, the downstream movement of the PHV toward the cylinder is accompanied with its bed-approaching movement and decreasing in size, and the opposite is true. The circulation strength of the PHV decreases and increases dramatically in the region downstream of its time-averaged position when the PHV approaches and departs from the cylinder, respectively. Meanwhile, mechanisms responsible for the generation, movement, variation, and disappearance of the PHV are re-investigated and enriched based on its interactions with vortices in the separation region and structures in the incoming flow. The obtained change trends of the features of the PHV and the underlying mechanisms for its evolution are valuable for predicting and controlling the initial stage of the local scour in front of cylinders.
Keywords: turbulent horseshoe vortex; evolution of vortex; circular cylinder flow; open channel turbulence turbulent horseshoe vortex; evolution of vortex; circular cylinder flow; open channel turbulence
MDPI and ACS Style

Chen, Q.; Yang, Z.; Wu, H. Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel. Water 2019, 11, 2079.

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