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Is it possible to override a dependent variable?
Posted 20 janv. 2012, 14:31 UTC−5 Version 4.2a 2 Replies
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Hi everyone,
I've have a model in which I solve a number of coupled phenomena including temperature using a time-dependent solver. I then want to cool down my model to see the deformation at room temperature but I don't need to see the transition. Right now this is really slowing down my model because it is require so many time-steps to model.
Ideally I would like to be able to:
Run a Transient model.
Stop it.
Run a second transient model with the temperature at a different value. (without the temperature physics mode)
Does anyone have any ideas how to override the value of a dependent variable for part of the model? I could make an additional variable like T_fix to do it and use that everywhere instead, but that would require very substantial changes to the model so I'm look for a more elegant solution.
Is overriding a variable even supported by Comsol? All my attempts produce a duplicate variable name error.
I've have a model in which I solve a number of coupled phenomena including temperature using a time-dependent solver. I then want to cool down my model to see the deformation at room temperature but I don't need to see the transition. Right now this is really slowing down my model because it is require so many time-steps to model.
Ideally I would like to be able to:
Run a Transient model.
Stop it.
Run a second transient model with the temperature at a different value. (without the temperature physics mode)
Does anyone have any ideas how to override the value of a dependent variable for part of the model? I could make an additional variable like T_fix to do it and use that everywhere instead, but that would require very substantial changes to the model so I'm look for a more elegant solution.
Is overriding a variable even supported by Comsol? All my attempts produce a duplicate variable name error.
2 Replies Last Post 5 juil. 2012, 13:41 UTC−4
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Posted:
1 decade ago
Hi
you can run a transient model for a given time, then link to a sationary one, and then relaunch a tranisnt one. by getting the initial conditions of one to be loaded from the preceding one. But today (it's supposed to be improved in the future releases once, I have heard) you have to update your BC conditions accordingly. Among others the "t" variable becomes undefined when you exit a time series, and relaunch a stationary case.
For that define a Parameter t=whatever_fits_you[s], COMSOL will overwrite it when you run a time series, and just use it for the other cases.
It requires some inventive action, but it works nicely ;) Check the settings of the solver Derived variable sub-nodes
--
Good luck
Ivar
you can run a transient model for a given time, then link to a sationary one, and then relaunch a tranisnt one. by getting the initial conditions of one to be loaded from the preceding one. But today (it's supposed to be improved in the future releases once, I have heard) you have to update your BC conditions accordingly. Among others the "t" variable becomes undefined when you exit a time series, and relaunch a stationary case.
For that define a Parameter t=whatever_fits_you[s], COMSOL will overwrite it when you run a time series, and just use it for the other cases.
It requires some inventive action, but it works nicely ;) Check the settings of the solver Derived variable sub-nodes
--
Good luck
Ivar
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Posted:
1 decade ago
I just wanted to say that I found a way to do this in 4.3 in case anyone comes across this post when searching.
I used two time-dependent steps. For each of the steps you can now enable and disable model tree items. So, I made a set of variables/equations which are disabled in the first one and enabled in the second one, and I disabled the physics module in the second one.
In my specific case I'm doing heat transfer in the first time-step and this is disabled in the second one. I then enable a set of variables with the same name as the dependent variable thus taking its place.
This new feature seems extremely powerful!
I used two time-dependent steps. For each of the steps you can now enable and disable model tree items. So, I made a set of variables/equations which are disabled in the first one and enabled in the second one, and I disabled the physics module in the second one.
In my specific case I'm doing heat transfer in the first time-step and this is disabled in the second one. I then enable a set of variables with the same name as the dependent variable thus taking its place.
This new feature seems extremely powerful!