Tidal averaging and models for anisotropic dispersion in coastal waters

Abstract

Several methods for the computation of long-term approximate solutions of the advection-diffusion equation in tidal waters are discussed. The time step used is a tidal period and the effect of tidal fluctuation is represented by a space-varying diffusion tensor. Further, a new method is presented that allows for more complicated dispersion patterns than can be obtained by the anisotropic diffusion operator. The method is applied to the Dutch Coastal waters, where horizontal and vertical density gradients cause anisotropic and irregular dispersion. Numerical results are compared with a solution, computed with small timesteps and tidal velocities.