THE MODELING OF THE FREE-SURFACE FLOW OF WATER OVER TOPOGRAPHY

A numerical model is developed for the flow of water over a bottom topography that is characteristic of sandwaves found in the coastal and river estuary environment. Turbulence closure is achieved at the level of the turbulence energy equation and the Reynolds stresses are parameterised in terms of a gradient transfer law and an assumed partitioning of the turbulence energy between different components of the flow. The pressure derives from both hydrostatic and hydrodynamic contributions. An experiment is performed for steady-state flow over a sequence of asymmetrical sandwaves and it is shown that there is flow separation over the lee slope of a sandwave. In this case, it is shown further that flow separation is a consequence of the inclusion of the hydrodynamic pressure contribution. A comparison is also made between non-hydrostatically and hydrostatically determined values of other mean and turbulent flow quantities.