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MEFD simulates the dispersive processes of conservative substances in the bidimensional hydrodynamic systems, in which the flow primarily happens on the horizontal plane and there are not present substantial stratification phenomena. The dispersion differential equation varies completely his typology, from a parabolic form to an hyperbolic one, in function of the different relative importance that can assume the convective terms compared to the diffusive ones. For this motive, quite a lot methods of resolution, proposed in the past but still today often used, are not absolutely able to eliminate a wide series of annoying and harmful numerical problems (onset of a diffusion not physical but numerical; oscillations in the solution; influence operated on the results of the model by the orientation of the network in the case of finite difference methods; incapability to preserve correctly mass).
MEFD, following the more recent numerical methods, is able to almost entirely eliminate all the problems cited above, determining the solution with the method of the characteristic lines joined to the method of the finite elements (MMOC). The numerical algorithm allows at first to follow the trajectories of the particles along the characteristic lines of the flow, ignoring the diffusion and overcoming, in this way, the greatest numerical obstacles. The technique of the finite elements is subsequently considered to complete the resolution of the equation. |
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