Development And Application Of A Shallow Water Flow Model HDM-2D

Abstract

In this study, an unsteady 2D depth-averaged flow model, HDM-2D was developed by employing the finite element algorithm. The shallow water equations were weighted by SU/PG test function of which the shape is deformed by the current direction to introduce balancing diffusion only in the flow direction. The nonlinearity of the discretized momentum equations was linearized by Newton-Raphson method. Triangular or rectangular element with C0 interpolation function can be mixed together in the construction of geometry and the linear set of equations was solved by frontal method. The HDM-2D features (1) the incorporation of secondary current effect by dispersion stresses; (2) the reproduction of convection-dominated or supercritical flow by SU/PG scheme; (3) the adjustment of the internal wall velocity by Navier-slip condition; (4) the imposition of skewed inflow velocity profiles by beta function; (5) the provision of eddy viscosity by constant, parabolic, and Smagorinsky turbulence models; (6) the inclusion of bottom shear stress by either quadratic Manning’s law or bed friction factor; and (7) the representation of wetting and drying by flux blocking method, which can be extended into inundation analysis model. To increase the applicability and user convenience, the HDM-2D was coupled to a 2D advection-dispersion model, CTM-2D to consider the flow and the transport phenomenon. The flow and transport models were combined into a software suite RAMS (River Analysis and Modeling System) to interface the solvers with the pre- and post-processor. Therefore, RAMS supports the mesh generation, the model control, the result view, and the exportation to SMS geometry or Tecplot data files. Several applications of HDM-2D in RAMS environment have shown that the HDM-2D gives accurate prediction of the flow characteristics in a variety of free surface problems and expected to be served as a useful tool for practical design