Multiple outflows with priority

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danguzzo
Junior Member
Posts: 12
Joined: Wed Jan 22, 2020 12:10 pm
Vensim version: DSS

Multiple outflows with priority

Post 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
Administrator
Super Administrator
Posts: 4573
Joined: Wed Mar 05, 2003 3:10 am

Re: Multiple outflows with priority

Post 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)
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391

Units are important!
http://www.bbc.co.uk/news/magazine-27509559
danguzzo
Junior Member
Posts: 12
Joined: Wed Jan 22, 2020 12:10 pm
Vensim version: DSS

Re: Multiple outflows with priority

Post 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!
Administrator
Super Administrator
Posts: 4573
Joined: Wed Mar 05, 2003 3:10 am

Re: Multiple outflows with priority

Post by Administrator »

You shouldn't have simultaneous equations using this. As I said, it would really help if you uploaded something.
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391

Units are important!
http://www.bbc.co.uk/news/magazine-27509559
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