Sebastien Lahaye, Remy Baraille, and Yves Morel, SHOM/CMO
A barotropic model has been designed, first in 1D then in 2D, to take into account the possibility of drying or wetting some areas. The model numerics are based on what exists in HYCOM to deal with vanishing layers (Zalesak scheme for the continuity equations and averaging of the pressure gradient terms for the momentum equations in particular). The model has been tested in academic configurations using exact analytical solutions where gravity wave oscillations induce periodic wetting/drying of part of a basin. The model is stable and performs well as far as the water depth is concerned. The velocity field seems more problematic, and seems to diverge from the analytical solution when the coriolis term is taken into account : a mean geostrophic current develops in the area where wetting and drying occurs.
To deal with the barotropic tide in some areas, the HYCOM model has been transformed using the previous results. The new schemes allowing wetting/drying has been implemented in the barotp.f subroutine. Some tests have been performed in realistic configurations in the French/English Channel, which are promising : the model is stable and the comparison between the results and observations of shoreline displacements are good.