Author(s): Michele Palermo; Sahameddin Mahmoudi Kurdistani; Stefano Pagliara

Linked Author(s): Michele Palermo, Stefano Pagliara

Keywords: bed morphology; hydraulics; rock sills; scour; unsteady flows

Abstract: Recently, rock sills have been widely used as an eco-friendly means of stabilizing rivers, but there has been very little systematic research to define their performance and produce design guidance. To the best of authors’ knowledge, most of studies present in the literature focus on the analysis of the equilibrium configuration under steady flow condition. However, in practical applications, it is extremely useful to understand scour mechanism during flood events, i.e., under unsteady flow condition. To narrow this gap of knowledge, tests were conducted at the hydraulic laboratory of the University of Pisa. Namely, linear rock sills were simulated in a dedicated channel with a uniform bed material. Two different sill configurations were tested by varying the inclination of the structure in plan view relative to the channel wall. Furthermore, reference tests were initially conducted under constant discharge (steady case), up to the equilibrium condition. Then, tests were repeated under unsteady flow condition, by simulating different inflow hydrographs, characterized by the same maximum discharge as corresponding reference tests. More specifically, unsteady tests were performed by varying the discharge increment and their duration, allowing us to understand the effect of such parameters on the resulting equilibrium morphology. Overall, it was observed that scour features and their evolution are affected by inflow conditions. Finally, we also provide insights on the erosion process and corroborate the applicability of the phenomenological theory of turbulence-based approach recently developed by Bombardelli et al. (2018).

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

Year: 2024