Modeling flows and sediment concentrations in a sloping channel with a submerged outlet using a hybrid finite-analytic approach

Abstract

This paper presents the development of a hybrid finite-analytic (HFA) based model for simulating flows and suspended sediment concentrations along a sloping channel with a submerged outlet. This model solves Reynolds-averaged Navier–Stokes equations and sediment transport equation in a staggered grid system. The spatial discretization of the hybrid finite-analytic expression is formulated using the locally linearized analytical solutions. The performance of HFA scheme in terms of the damping and diffusion effects is examined through the analytical procedure of the von Neumann stability analysis. The model is first tested with several selected cases and the results are shown to compare well with analytical solutions. The model is then extended to simulate the flows in a reservoir with a sloping bottom and a submerged two-dimensional (2-D) orifice downstream. The computed horizontal velocity vectors and the reattachment length show reasonable agreement with Jin’s (1990) [26] experimental measurements. Comparisons of computed sediment concentrations are made with other published numerical results. The model is also applied to study the three-dimensional (3-D) flows in a reservoir with a scouring funnel like bottom topography and a 3-D orifice outlet. The complicated 3-D flow pattern in front of the orifice is presented and discussed.