Advection

In the advection phenomena, we suppose that a chemical transported by a mobile phase mixes instantaneously with the chemical already present in the cell:

 

 fig8a.jpg (17782 byte)  fig8b.jpg (17912 byte)

                        (a)                                                              (b)

Fig. 1: Inflow of the chemical C in the cell (a); outflow of the chemical C form the cell (b)

 

The variation in the amount of chemical within the cell is given by the difference between the chemical that comes into the cell (Fig. 1a) and the chemical that flows out from the cell (Fig. 1b). The amount of chemical QC ([m]) in the phase a that in a step of CA flows in (or out) the cell in the direction i is:

 figM.jpg (1529 byte)

where J?,i is the flow ([l3 t-1]) of the phase ? in the direction i in the cell and Ci is the concentration of the chemical in the cell i of the neighbour ([m l-3]).