Abstract

This paper reports a comprehensive study of the major scour agent around bridge piers: the turbulent horseshoe vortex. The intricate and inherently unsteady characteristics of the junction flow are captured within a series of scaled laboratory experiments. We applied the state-of-the art Time-Resolved Digital Particle Image Velocimetry (TR-DPIV) technique to measure the velocity field at the centerline plane of symmetry upstream of a cylindrical model. Three levels of Reynolds numbers (Re D ) based on the obstacle diameter were studied: 26,000, 48,000 and 117,500. We evaluated the effect of this factor based on the time-averaged analyses of velocity and vorticity. Basic statistical analysis of the fluctuating velocity components provided insight to the physical mechanism that governs the behavior of the horseshoe vortex at the aforementioned levels of Re D .

Highlights

  • Erosion of the loose boundary material around bridge piers poses a significant threat to the structural integrity of the bridge

  • Despite the remarkable progress that has been made in the study of the horseshoe vortex dynamics and the unsteady characteristics of junction flows, a comprehensive study that would incorporate the latest advances in experimental fluid mechanics is still lacking

  • The main purpose of this experimental study was to test the hypothesis that the Reynolds number plays a role in shaping the dynamics of the turbulent horseshoe vortex

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Summary

Introduction

Erosion of the loose boundary material around bridge piers poses a significant threat to the structural integrity of the bridge. Hydrogen bubble visualizations highlighted the trend for increased flow complexity with Reo. The existence of a positive relation between the size of vortex system and the Reynolds number was reported. These states were documented in the probability density functions of the streamwise and vertical velocity components, where two distinct peaks were identified.

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