A three-dimensional fixed grid model for shallow-water flow

A three-dimensional fixed grid model for shallow-water flow

Bijvelds, M.D.J.P.

Civil Engineering and Geosciences

Hydraulic Engineering

1998-01-01

In this report the implementation and testing of a numerical model that is based on a Cartesian fixed grid in vertical direction is described. The model uses the shallow-water equations and accounts for effects of stratification. In stratified environments, the terrain-following 0-transformation, which is often used in shallow-watermodels, is known to introduce numerical errors in computing the baroclinic pressure gradient, especially in regions with varying depth. Although quite some research was carried out in the past on the improvement of the implementation of the baroclinic pressure gradient, it still is not entirely clear to what extent the errors related to this problem harm computational results. In order to compare both approaches, i.e. the Cartesian fixed grid and the co-ordinate system based on the o-transformation, in a consistent way, identical discretizations of time and space were employed in both models, This allows to draw conclusions about the errors that are related to the co-ordinate system used, without interference of other uncertainties. It is shown that for relatively simple flow configurations, both models yield comparable results. In case of stratified flow over a rapidly varying bathymetry, significant differences between the models were observed.

flow models
cartesian grid
shallow water equations
srtatification

http://resolver.tudelft.nl/uuid:bc1f6ff8-53d6-45e1-bcb7-ab0b24a8ee23

TU Delft, Department of Hydraulic Engineering

Report 6-98 for Rijkswaterstaat, RIKZ.

Institutional Repository

report

(c) TU Delft, Department of Hydraulic Engineering