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general question

Franziska Gebhard, modified 2 Years ago.

general question

Youngling Posts: 18 Join Date: 4/20/17 Recent Posts


two general question:

IMod works with the finite difference method. The area is divided into cells. In each cell there is a node where the calculations take place.
1.) WHERE are the nodes in iMOD? In the middle of the cell or at the interfaces of the grid lines?

2.) And how does iMOD handle the calculations when a layer boundary passes exactly through a cell? For example, one half of the cell has the transmissivity of 34 m/d and the other half has a transmissivity of 10 m/d.

I would appreciate an answer.

Best regards


Frans Roelofsen, modified 2 Years ago.

RE: general question

Padawan Posts: 99 Join Date: 11/11/13 Recent Posts

Hi Franzi, 

1. iMOD models are calculated using the standard MODFLOW concepts/sourcecode. This means that also in iMOD, the nodes are in the middle of a cell

2. Perhaps the explanation in the manual in chapter 12.4 (KDW Transmissivity) and especially figure 12.3 can help you on how MODFLOW handles transmissivity.
If I understand your question correctly: a layer boundary cannot pass through a cell. There are 2 situations: 1) or the TOP/BOT is given in the Run file as the z interface between layers or 2) no TOB/BOT is given (use KDW for transmissivity) and than a layer/cell characteristic is binary; active or in-active.
In case your question is about the iMODFLOW run and the boundary conditions; you need to use the same top/bot boundary definition as in the iMODFLOW run.


Kind regards, Frans