Quadrant analysis of flow-structure interaction influenced by circular bridge piers around a rectangular abutment

This study presents a detailed experimental investigation of three-dimensional turbulent flow structures and scour patterns around bridge piers and a rectangular abutment placed on a rough bed. Using an Acoustic Doppler Velocimeter (ADV) within a controlled laboratory flume, spatial variations in turbulence intensities, Reynolds Shear Stress (RSS), and quadrant-based turbulence events were measured across longitudinal, transverse, and vertical directions. The analysis focuses on flow–structure interactions, highlighting the roles of sweep and ejection events in sediment transport and scour development upstream and downstream of the abutment, as well as in the gap between the pier and abutment. Results reveal that sweep events dominate near the abutment, promoting increased bed shear stress and localized scour, while ejection events become more prominent downstream, facilitating sediment transport and deposition, thereby reducing scour intensity. The highest turbulence intensities, RSS, and quadrant event contributions occur near the abutment face and within the constricted flow zone between the pier and abutment, indicating strong flow obstruction effects and vortex formation. The sweep-to-ejection (STE) ratio confirms a transition from active scour driven by sweeps near the structure to sediment stabilization due to ejections further downstream. Overall, these findings underscore the critical influence of near-bed turbulence and coherent flow structures on scour morphology and sediment dynamics. Such insights are essential for designing effective scour protection and hydraulic structures that are resilient to turbulence-induced erosion. • Burst cycle characteristic study of flow through two bridge piers and an abutment. • Study includes quadrant-based flow turbulence and Reynolds Shear Stress (RSS) distributions. • Scour patterns co-influenced by bridge piers and abutment has been used for studying the impact to flow. • ADV experiments were carried out to analyse the three-dimensional flow field of the investigated flow case.