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How to specify a concentration in a cell without complete mixing?

Javier García Alba, modified 5 Years ago.

How to specify a concentration in a cell without complete mixing?

Youngling Posts: 12 Join Date: 1/4/12 Recent Posts
Hi,

We want to specify a concentration value in a cell (surface discharge). When we run the delwaq, the model do a complete mixing in the cell ((discharge flow*discharge concentration + cell concentration*volume cell)/(discharge flow+volume cell)), but we want to impose the concentration value in the whole cell without a complete mixing process. Actually, we want to impose initial dilution concentration directly in the cell. Is it possible?

Javi
Christophe Thiange, modified 5 Years ago.

RE: How to specify a concentration in a cell without complete mixing?

Jedi Knight Posts: 125 Join Date: 11/15/12 Recent Posts
Hi Javi,

You cannot use a simple load to impose a concentration on a particular segment because there will always be other fluxes to/from that segment.

The user-defined wasteload functionality (Appendix E of the user manual) allows you to program a load based on the concentration in a given segment at each time step. If the volume of your target segment does not change, you could define such a wasteload to add (or remove) the required mass to obtain the desired concentration in your segment.
As far as I know, there no way to access a segment's volume from the user-defined wasteload routine, hence if the volume of your segment does change over time you'll have to be creative (like hardcoding a time series of that segment's volume in your wasteload routine).

Can I ask why you want to impose a concentration inside a segment? Maybe there are other means to that end.

Regards,
Christophe
Javier García Alba, modified 5 Years ago.

RE: How to specify a concentration in a cell without complete mixing?

Youngling Posts: 12 Join Date: 1/4/12 Recent Posts
Hi Christophe,

Thank you for your quick response. I want to couple the results of a initial dilution model with the far-field (using delwaq). The problem is that delwaq model calculates a complete mixing in the dicharge cell and I want to impose the obtained concentration with the initial dilution model.

I think it could be an improvement, if the user can impose a fix concentration directly in the discharge cell with the GUI.

Regards,

Javi