Three-Dimensional Numerical Investigations of the Flow Pattern and Evolution of the Horseshoe Vortex at a Circular Pier during the Development of a Scour Hole

Abstract

In the current study, a three-dimensional CFD model is utilized to investigate the variation of the flow structure and bed shear stress at a single cylindrical pier during scour development. The scour development is presented by seven solidified geometries of the scour hole, collected during previous experimental work at different scour stages. Different turbulence models are evaluated and the (k-ω) model is chosen due to its relative accuracy in capturing the flow oscillation and vortex shedding at the pier downstream side with personal computer computational and storage resources. The numerical results are verified against dimensionless parameters from different previous experimental works. This research describes in detail the flow structure and bed shear stress variations through seven stages of the scour hole development. The dimensionless area-averaged circulation coefficient (Ψi) is developed to evaluate the changes in the vortex strength through the scouring process by eliminating the calculation area effect. It was concluded that the circulation in the (Y) direction is the main driving factor in the development of the scour hole more than the circulation in the (X) direction. The ratio between the horseshoe vortex (HV) mean size and the scouring depth (DV/dS) in addition to the location of the maximum bed shear stress are investigated during different stages of the scour development.

Local Scour at Complex Bridge Piers in Bangladesh Rivers: Reflections from a Large Study

“…In this study, the local scour at the bridge pier was estimated using empirical equations. Though numerical simulations and flume experiments are used to understand the scour process, to predict the bed shear stresses due to different pier configurations, and to understand the performance of different countermeasures in reducing the scour potential [13][14][15], the resource (human, technical and financial) and time constraints often do not allow the use of such methods in scour prediction, especially if a large number of bridges are to be studied within a short period. Moreover, the numerical investigation has so far been conducted with a uniform circular pier, square cross-section, and piles of different spacing [14], and no studies are reported on the complex pier.…”