Hydrodynamic shock in Rivers: Physical and numerical modeling of flow structures in tsunami-like bores.

This article focuses on the detailed numerical investigation of turbulent hydrodynamics induced by three-dimensional (3D) undular bores propagating upstream against steady flows in rectangular channels, with implications for understanding tsunami-like bores in rivers. Using large eddy simulation (LES) of the Navier–Stokes equations and synthetic eddy method (SEM) to reproduce turbulent inflow conditions, the study compares two- and three-dimensional simulations under various bore generation methods (dam break, fully or partially closed gates) and initial flow conditions. Key findings include the identification of three distinct flow scenarios beneath bores—complete flow reversal, oscillating flow, and no flow reversal—and the critical role of Reynolds number (around 5 × 10^4) in triggering near-bed turbulence and eddy shedding, which significantly alter flow structures despite similar free-surface profiles. The results demonstrate that 3D simulations with turbulent inflow better capture complex flow features such as cross-waves and coherent turbulent structures, highlighting the necessity of incorporating realistic turbulence for accurate modeling of positive surges relevant to tsunami propagation in estuarine and riverine environments.