Author(s): Nelson Cely-Calixto; Alberto Galvis; Gustavo Carrillo-Soto; Melquisedec Cortes-Zambrano

Linked Author(s): Alberto Galvis

Keywords: Longitudinal walls; Scour; Flow3D; Computational model

Abstract: Longitudinal walls are structures installed in riverbeds as a means of protection and containment. However, being structures that obstruct the flow in the channel, they are susceptible to cause erosive processes in their vicinity, generating failures and progressively increasing scour problems. The phenomenon of subsiding on hydraulic structures, such as longitudinal walls, which are considered complex processes, where turbulence is generated by the collision of the flow with the structure, causing the formation of vortices, which produce exposure in the foundations of the hydraulic structure. In recent years, a significant number of studies have been conducted on scour in hydraulic structures, especially for bridge abutments and piers. However, studies concerning longitudinal walls have been developed to a lesser extent. In the present study, a set of experiments were run in a physical model, where typical river conditions with well-graded granular bed were simulated in a test channel HM 162 where a longitudinal wall was installed without flow incidence at the entrance edge, to generate values of the maximum scour depth at the base of the longitudinal structure. The measurement of the pit produced by scour in the bed was developed using a scanner with which the bed material was recorded before and after the passage of the flow. Due to the interaction between the three-dimensional (3D) flow pattern and the bed material, the scour process in the wall of a longitudinal wall is complex. The particular use of the empirical scour formula may not be sufficient to evaluate scour under turbulent flow conditions. The objective of this study was to calibrate and validate the numerical model of the scour processes in longitudinal walls in rivers with well-graded granular beds by using a computational fluid dynamics software, Flow3D, as it uses the Reynolds Average Navier Stokes (RANS) equation closed with a k-ԑ turbulent model. The computational model has implemented a stable and convergent solution for various forms of hydrodynamic structures, taking into account a constant time interval and a fixed bed load coefficient. The model also provided accurate information on flow velocity, bed shear stress, and water surface.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221636

Year: 2022