Influence of Scour Development on Turbulent Flow Field in Front of a Bridge Pier

Abstract

This study concerns the turbulent flow field influenced by the scour development around a bridge pier. The scour hole evolution as well as the temporal variation of scour depth around the pier were firstly analyzed. Subsequently, the flow fields in front of the pier at different instants during the scour process were measured using particle image velocimetry (PIV). It shows that the scour depth at the pier front exceeds that of the pier side at the later scouring stage. The temporal development of scour depth can be well predicted by a simple practical engineering model based on an exponential function with a change in the two adjustable coefficients. The flow field indicates that with the development of scour hole, the downward flow in front of the pier becomes more prominent, meanwhile the flow becomes more turbulent. The variation tendency for both velocities and turbulence intensities along the streamwise direction in front the pier shows similarity. The Reynolds shear stress generally increases with developing scour hole, and the region with large value enlarges and moves upstream of the scour hole.

Experimental Characterization of the Flow Field around Oblong Bridge Piers

“…2U Ebed. This finding is consistent with the results from the measurement of Dey and Raikar [8] and Li et al [21]. Downstream of the oblong bridge pier models, w decreases with x/h for all experiments (Exp.…”

“…To sum up, the mean flow velocities for the six fixed experiments indicate that with the developed scour hole, the downward flow in front of the oblong bridge pier model becomes more prominent, and the flow becomes more turbulent due to the effect of a turbulent horseshoe vortex within the scour hole, as documented by previous researchers [21,43], among others.…”

“…Ataie-Ashtiani and Aslani-Kordkandi [18] investigated the ADV measurements of turbulent flow field around single, side-by-side and tandem pile groups with and without a scour hole. Their results corroborated that the in-depth understanding of the flow and turbulence influenced by the scour hole is essential to improving the prediction of scour depth, see [19][20][21] and references therein.…”

“…2U Ebed. This can be explained that as the scour evolves upstream, the bed slope increases due to the formation of the scour hole, and the flow velocity increases correspondingly [21]. In Figures 10a, 11a and 12a, the downstream vertical profiles of u (from J half-plane in Figure 5) are characterized by increasing magnitudes as they move away from the oblong bridge pier models.…”

“…2U Ebed, where a value of 0.40 ms −1 was considered. Unlike in other flow field experimental studies, see [21] and references therein, the velocity measurements were also allowed within the scour hole of the eroded bed experiments, which explains the negative values for elevations z below the initial flat bed level (see . As can be observed, vertical profile "1" of A is situated outside the upstream border of the scour hole in all experiments.…”