Author(s): Tommaso Lazzarin; Lei Xu; Saiyu Yuan; A. J. F. Hoitink; Daniele P. Viero
Linked Author(s): Saiyu Yuan
Keywords: Secondary flow; Density gradient; River confluence; Free-surface flow; SWEs
Abstract: At river confluences, transversal secondary currents generated by both streamline curvature and transversal density gradients influence the flow field and sediment transport. Thus, properly accounting for their effects in two-dimensional (2D) numerical models is important for accuracy. In this study, the 2D hydro-morphodynamic model of Lazzarin & Viero (2023) is enhanced with additional dispersive terms to account for secondary currents effectively in both fixed and mobile bed simulations. The proposed model solves the shallow water equations (SWEs) for the water flow, coupled with advection-diffusion equations for the temperature and for the intensity of secondary currents (i.e., helical flow) driven by channel curvature and transverse density gradients. A morphodynamic module computes sediment transport and bed evolution, incorporating specific dispersive terms that account for the non-uniform vertical profile of suspended sediment concentration. The model is applied to the Yangtze River and Poyang Lake confluence, and validated using ADCP field data (Yuan et al., 2021). Mobile-bed simulations are then conducted to assess the model ability in predicting the bed evolution.
Year: 2025