PhreeqcUsers Discussion Forum

Processes => Reactive transport modelling => Topic started by: Nicolas Jacquemet on 03/04/26 11:18

Title: Different lengths for cells ?
Post by: Nicolas Jacquemet on 03/04/26 11:18

Hi David,

With -lengths under TRANSPORT, it is possible to define cells with different lengths (Delta x). But, obeying to the 'Courant condition' (equation 108 of the version 2 user's guide) implies that for a given time step and pore water flow velocity, Delta x has a unique value. Thus, can you explain why it is possible to define different Delta x's ?

Many thanks for your answer,

Nicolas J.

Title: Re: Different lengths for cells ?
Post by: dlparkhurst on 03/04/26 14:35

The cell volume is generally the same for each cel, regardless of the cell length. The cell volume is replaced each time step by the volume in the upstream cell. So, the velocity of the water in the cell is length divided by time step. Cells with different lengths have different velocities.

Title: Re: Different lengths for cells ?
Post by: Nicolas Jacquemet on 08/04/26 13:03

OK, thank you David for your answer.

Nicolas