Contaminant Transport Module: A dynamic Initial Inventory

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Jackson White

• December 15, 2025 06:34

Hi Jason/Rick, 

I am trying to build a model using the contaminant transport module. For a few of my cell pathways I have an Initial Inventory, which is connected to a function that converts a parameter linked to the dashboard to a load. Gold Sim doesn't seem to like that... as you can see below:

Originally, I had his conversion in a subsystem container as shown:

But now I've moved this whole part of the model out:

Is there a workaround this kind of problem? I do need to keep this part of the model connected to the dashboard.

Thanks in advance, 

Jackson

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  Rick Kossik

  • December 15, 2025 15:51

  So the Dashboard controls a Data element, you have an Expression that is a function of that Data element, and it will not accept that in the Initial Inventory field?  That should work.  Can you send (via our Help Desk) a simplified version of this that illustrates the problem? Also, I did not understand your discussion regarding the Container this was in.  Can you elaborate on that?

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  Jackson White

  • December 15, 2025 22:29
  • Edited

  Hi Rick, 

  Thanks for your response. I'll pass the problem on to the Help Desk.

  Regarding the discussion on the container, I have created a sketch below:

  

  For some context on what I'm working on:

  This part of my model is in a container, to keep the overall model tidy. What I am aiming to achieve in this container is to scale a vector with concentration data ("Chem_vector") by a scalar ("Chem_scalar") which is connected to the dashboard. To do so, "Chem_scalar" is converted to a parameter that is contained in "Chem_vector", using the expression named "Conversion". The output from "Conversion" then scales "Chem_vector" using the expression named "Scale_vector". This concentration is converted to a load via the "Initial_Inventory_input" expression and is used as an input in the Cell Pathway.

  When I run the model, I get the "Error in element: Cell Pathway" message. If I understand the message correctly, the cell pathway is not recognizing the "Initial_inventory_input" expression as an input (1), because the expression is in a container (2) and (3). 

  I did find this message strange because I have the same approach in a different container: Data connected to a dashboard, some expressions converting the data to a load, and the load is used as an input to a cell pathway. There have been no issues in those containers so far.

  I'll forward a more elaborate request to the Help Desk.

  Thanks Rick and kind regards, 

  Jackson 

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  Jackson White

  • December 15, 2025 22:09

  I forgot to add; I did try taking this part of the model out of the container and running it, but I still got the same message.

  Kind regards, 

  Jackson 

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  Jackson White

  • December 18, 2025 06:19

  I thought I would post how I solved my own problem. It was very simply fortunately; I had a cell pathway set with an input rate flowing into another cell pathway with set with an initial inventory. I believe this set up was creating conflicts in the software. I set both cells to a constant input rate, but I suspect that as long as both cells have the same cell inventory there should be no conflict.

  Kind regards, 

  Jackson 

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  Rick Kossik

  • December 18, 2025 14:56

  It appears that your Initial Inventory input is a function of the Reservoir element named "Pool"?  This is the cause of the problem.  An Initial Inventory cannot be a function of time.  All of the outputs of a Reservoir element can change with time.  Hence, GoldSim would throw an error when you made the Initial Inventory a function of the Reservoir element.

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