3D Numerical Modeling of Flow and Sediment Transport in Open Channels

TLDR

A 3D numerical model for calculating flow and sediment transport in open channels is presented. The model solves the full Reynolds‑averaged Navier–Stokes equations with a k‑ε turbulence closure, uses a 2D Poisson equation for free‑surface elevation, simulates suspended load by a convection‑diffusion equation with empirical settling velocity, and models bed load with a nonequilibrium approach, all discretized by a finite‑volume method on an adaptive, non‑staggered grid. The suspended‑load model was tested for net entrainment and deposition, and the full 3D total‑load model was validated in a 180° channel bend with movable bed, showing generally good agreement with measurements.

Abstract

A 3D numerical model for calculating flow and sediment transport in open channels is presented. The flow is calculated by solving the full Reynolds-averaged Navier-Stokes equations with the k − ε turbulence model. Special free-surface and roughness treatments are introduced for open-channel flow; in particular the water level is determined from a 2D Poisson equation derived from 2D depth-averaged momentum equations. Suspended-load transport is simulated through the general convection-diffusion equation with an empirical settling-velocity term. This equation and the flow equations are solved numerically with a finite-volume method on an adaptive, nonstaggered grid. Bed-load transport is simulated with a nonequilibrium method and the bed deformation is obtained from an overall mass-balance equation. The suspended-load model is tested for channel flow situations with net entrainment from a loose bed and with net deposition, and the full 3D total-load model is validated by calculating the flow and sediment transport in a 180° channel bend with movable bed. In all cases, the agreement with measurements is generally good.