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How to make a dependent variable does not take negative values?
Posted Oct 19, 2011, 4:17 p.m. EDT Studies & Solvers 3 Replies
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Hello,
I am modeling microorganiamo growth in a bioreactor, using the Chemical Engineering Module.
The question is, as time passes, the organism grows and feeds on a substrate, the substrate concentration goes down to 0. The thing is, if the simulation continues, the concentration is negative and I do not want that to happen.
In short, how do you do for the variable does not acquire negative values?
Sorry for my bad English. Thanks.
I am modeling microorganiamo growth in a bioreactor, using the Chemical Engineering Module.
The question is, as time passes, the organism grows and feeds on a substrate, the substrate concentration goes down to 0. The thing is, if the simulation continues, the concentration is negative and I do not want that to happen.
In short, how do you do for the variable does not acquire negative values?
Sorry for my bad English. Thanks.
3 Replies Last Post Sep 2, 2013, 3:49 p.m. EDT
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Posted:
1 decade ago
Carlos,
in case the dependant variables in a model go to unphysical values (negative concentration in your case) then my assumption would be that the equations or boundary conditions are not suited for the phenomenon you want to model.
Unfortunately I don't have the Chemical Engineering module, so I cannot give more practical advice.
Cheers
Edgar
in case the dependant variables in a model go to unphysical values (negative concentration in your case) then my assumption would be that the equations or boundary conditions are not suited for the phenomenon you want to model.
Unfortunately I don't have the Chemical Engineering module, so I cannot give more practical advice.
Cheers
Edgar
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Posted:
1 decade ago
Thank you Edgar.
I'll wait to see if anyone can help me.
I'll wait to see if anyone can help me.
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Posted:
1 decade ago
Hi,
You can switch to a segregated solver and use "lower limit" option provided. there you can force the lowest value the variable can get and if it goes below that value solver automatically overrides it with the limit you have defined.
I am using this in my problem for continously decreasing unreal concentration values and it is working pretty fine.
Best,
arda
You can switch to a segregated solver and use "lower limit" option provided. there you can force the lowest value the variable can get and if it goes below that value solver automatically overrides it with the limit you have defined.
I am using this in my problem for continously decreasing unreal concentration values and it is working pretty fine.
Best,
arda