Numerical investigation of the scour around a diamond- and square-shaped pile in a narrow channel

In this paper, a numerical investigation is conducted to study the scour dynamics around vertical squareand diamond-shaped piles in clear-water and live -bed conditions. The focus is particularly on cases involving narrow channels, aiming to examine the differences compared to more extensively studied scenarios, such as wide channels with circular piles. This work employs a Large Eddy Simulation (LES) model to simulate the turbulent flows around the structures. The hydrodynamic model is based on the Navier-Stokes equations in sigma-coordinate, and the bed evolution is simulated by solving the Exner-Polya equation. The governing equations are solved using a second -order unstructured finite-volume method. The model is initially validated through a comparison with experimental data and numerical results found in the literature. Subsequently, it is applied to conduct a comprehensive study, enhancing our understanding of the various conditions influencing the scour process. The results indicate that the shape of the piles has different effects on the scour depth under clear-water and live -bed conditions. In live -bed conditions, the simulations reveal a deeper scour around the square-shaped pile compared to the diamond-shaped pile at the equilibrium stage. Conversely, an opposite behavior is observed in clear-water conditions, with a deeper scour around the diamond pile. Moreover, this behavior is consistent across both narrow and wide channels. It is discovered that, in clear-water conditions, the evolution of the scour in a narrow channel reaches equilibrium faster than in a wide channel, leading to a deeper equilibrium scour hole in the wide channel scenario.