Author(s): T. I. Eldho; Gaurav Misuriya

Linked Author(s): Eldho T.I.

Keywords: Pressure flow; Hydrodynamics; Bridge submergence; Scour; Vertical contraction; PIV

Abstract: The likelihood of bridge submergence has increased as the frequency of occurrence of flood increased due to climate change. During a submergence event, the flow vertically contracts, accelerating upto the transition from atmospheric to pressure flow beneath the bridge. The pressure flow increases the bed-shear stresses and velocity gradient, which raises the risk of bridge failure due to scouring. For a fair estimation of scour depth, a detailed understanding of the turbulence related to physical phenomenon is necessary. Therefore, this study investigates various turbulent characteristics and scour under a submerged deck supported by a circular pier over plane rigid bed and sand bed conditions and results are compared with the open flow condition (without submerged deck). The 2-dimensional instantaneous velocity components were measured using Particle Image Velocimetry (PIV). The variation of the average turbulent strength in terms of turbulent kinetic energy and Reynolds shear stress was studied to locate the deviation of possible critical location for scour under pressure flow condition when compared with open flow condition. Further, the characteristics of scour hole in the sand bed are analysed for similar flow conditions. It has been noted that determining the maximum scour depth beneath a bridge deck in the presence of piers is not as straightforward as combining scour depths calculated separately for the deck and pier conditions. Nevertheless, it has been observed that the point of maximum pressure scour aligns with the location of maximum turbulent intensity when the flow conditions are identical.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024