Author(s)

J. S. Antunes do Carmo & J. L. Carreiras

Abstract

The numerical model MECCA (Model for Estuarine and Coastal Circulation Assessment) – which was developed to simulate tidal currents, density currents or those generated by wind action, in bays or coastal zones (Hess, 1989) – is a \“three-dimensional model”, or a quasi-3D model, which is able to satisfactorily simulate complex three-dimensional flows. The MECCA model algorithm is based on the continuity equation (under the non-compressibility hypothesis), on the Navier-Stokes equations (considering hydrostatic equilibrium and the Boussinesq hypothesis) and on conservation equations for temperature and salinity. It is structured in two modes: the external-mode, obtained by vertical integration of the Navier-Stokes equations, and the internal-mode, obtained by subtracting the equations for the external-mode velocity from the equations for the total velocity. The flow within the bottom boundary layer is alternatively described by a Prandtl type model or by a lDV model of the K-L type. We conducted a rigorous study of its characteristics and hydrodynamic capacities with the aim of extending the MECCA model to sedimentary dynamics applications (suspended and bedload transport). Numerical results were validated by comparisons with laboratory data and other numerical results and theoretical solutions. This work presents various simulations of the flow around structures commonly occurring in the fluvial and coastal environment, like structure pillars, breakwaters and piers. Particular attention has been given to the two-dimensional and three-dimensional structures of the flow characteristics. We also present sensitivity analyses of the model, using different grids, as well as the two implemented boundary layer models.

Keywords