Three-dimensional non-hydrostatic modeling of free-surface turbulent flows and transport of cohesive sediment.

摘要

A new three-dimensional finite-element model for the incompressible Navier-Stokes equations is developed and validated by comparisons with analytical solutions and experimental data. The model is specifically designed to simulate turbulent free-surface flow. Effects of buoyancy and thermally driven currents are also included. The finite element formulation is based on a Petrov-Galerkin scheme in conjunction with tri-quadratic interpolating functions. The equations are solved in true physical space without the use of a ;A companion finite element model is developed for the three-dimensional advection-diffusion equation and used to predict the fate and transport of cohesive sediments. The model accounts for flocculation and break up of colloidal particles by relating these mechanism to flow characteristics. In particular, the computed flow shearing rate is used to calculate the formation of flocs, their settling and resuspension.;The model is validated by numerous comparisons to analytical solutions for laminar flow in both confined and free-surface configurations. Comparisons are also made with experimental observations for both channel flows and cohesive sediment transport. Applications are presented for laminar and turbulent flow under the influence of thermal gradients, a gradually expanding channel with a free-surface, the recirculation resulting from an abrupt expansion and solute transport from a point source. The results are presented in variety of graphical forms including velocity vector fields, contour maps, and three-dimensional surfaces.