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Setting If statement in COMSOL ODE

Posted Oct 5, 2015, 9:21 p.m. EDT Version 5.0 4 Replies

JY Chan
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Hi, I am trying to solve an ODE in COMSOL (time-dependent) but i want the ode to be initiated only if the temperature is below certain value, say 272K. Is it possible to implement this in comsol?

Thanks
4 Replies Last Post Oct 7, 2015, 4:50 a.m. EDT
Walter Frei COMSOL Employee

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Posted: 9 years ago Oct 6, 2015, 9:23 a.m. EDT
Hello,
You may want to look at this material, it may point you towards an alternative approach to what you are attempting:
www.comsol.com/blogs/implementing-a-thermostat-with-the-events-interface/
www.comsol.com/blogs/using-the-previous-solution-operator-in-transient-modeling/
www.comsol.com/blogs/tracking-material-damage-with-the-previous-solution-operator/
Hello, You may want to look at this material, it may point you towards an alternative approach to what you are attempting: http://www.comsol.com/blogs/implementing-a-thermostat-with-the-events-interface/ http://www.comsol.com/blogs/using-the-previous-solution-operator-in-transient-modeling/ http://www.comsol.com/blogs/tracking-material-damage-with-the-previous-solution-operator/
JY Chan
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Posted: 9 years ago Oct 6, 2015, 9:45 a.m. EDT
Alright thanks :)
Alright thanks :)
JY Chan
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Posted: 9 years ago Oct 7, 2015, 12:49 a.m. EDT
If I want to apply a specific ODE in the region with temperature < 272K, like du/dt = F, but in other region where T>272, I wish to implement another ODE, du/dt=0. This means that depending on the temperature in that particular region, the ODE will switch. Can this be done in comsol?

Thanks
If I want to apply a specific ODE in the region with temperature < 272K, like du/dt = F, but in other region where T>272, I wish to implement another ODE, du/dt=0. This means that depending on the temperature in that particular region, the ODE will switch. Can this be done in comsol? Thanks
Gunnar Andersson COMSOL Employee

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Posted: 9 years ago Oct 7, 2015, 4:50 a.m. EDT
Use the following expression in the Source Term in the Distributed ODE node: ut-if(T<272,F,0)
Use the following expression in the Source Term in the Distributed ODE node: ut-if(T

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