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Multiple outflows with priority

Posted: Mon Feb 03, 2020 6:09 pm
by danguzzo
Hi,

In a given model part, I got one stock with three outflows => second-use, remanufacturing, and disposal. The priority is as written, first, they should get into SU, then reman, then recycling. It happens according to available infrastructures.
The reman outflow is limited by the EEE demand.

When I try to give priority to the flows through intermediate variables or fractions I either get 'Simultaneous initial value' or circular equation (or something like that).

Is there a function in Vensim that permits me to prioritise the flows?

If anyone would like to check the model, please let me know your GitHub user as the model is still on stealth mode :)

Thanks in advance

Re: Multiple outflows with priority

Posted: Mon Feb 03, 2020 7:55 pm
by Administrator
There is no Vensim function to do this. It would help if you uploaded something as we are just guessing if we cannot see something (even just copy/paste the level and three outflows).

To prioritise, you can do something like

stuff = integ (inflow - second use - remanufacturing - disposal , initial stuff)

second use = min ( stuff/time step - desired outflow )

remanufacturing = min ( stuff/time step - second use , desired remanufacturing rate)

disposal = min ( stuff/time step - second use - remanufacturing , desired disposal rate)

Re: Multiple outflows with priority

Posted: Mon Feb 03, 2020 8:19 pm
by danguzzo
Hey, thanks for your reply.

Restrict using this structure did not work for me. Led to simultaneous initial value equations.
Nevertheless, using the Active Initial in one variable solved the issue.

Regards!

Re: Multiple outflows with priority

Posted: Mon Feb 03, 2020 8:45 pm
by Administrator
You shouldn't have simultaneous equations using this. As I said, it would really help if you uploaded something.