Menu

Discussion Forum

New Discussion
Filtern

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

How I can appropriate / set a variable for temperature distribution on border?

Posted 26.09.2011, 03:51 GMT-4 Parameters, Variables, & Functions Version 4.2 4 Replies

Mikhail Polous
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello everybody!
I have already got a temperature field of the model. How I can appropriate / set a variable for temperature distribution on border?

Attachments:

4 Replies Last Post 29.09.2011, 03:10 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 26.09.2011, 07:09 GMT-4
Hi

the value you give is the value taken for eaxh mesh elements by COMSOL so if you give a function as variable ie. a T(z) and define this function via a Define Function ... then you will get a variable imposed temperature value depending on "z" (this applies to most variables and to all dimensions, COMSOL is fundamentally generalised)

--
Good luck
Ivar
Hi the value you give is the value taken for eaxh mesh elements by COMSOL so if you give a function as variable ie. a T(z) and define this function via a Define Function ... then you will get a variable imposed temperature value depending on "z" (this applies to most variables and to all dimensions, COMSOL is fundamentally generalised) -- Good luck Ivar
Mikhail Polous
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 28.09.2011, 08:55 GMT-4
Thank you for quick response, Ivar.
But the thing is that I don’t have to define the function T(z), as it is unknown in the very beginning – it can be acquired only as a result of calculation. I have to assign a variable to the still uncalculated temperature distribution on the element boundary. And then I'd like to use this variable for another function in a section (definition --> function), which depends on it.

Here is an example from another physics field:
We have a diod (2 parallel plates). I need to define the current density as a function of potential distribution on the plate boundary (this potential is initially unknown, as it can be acquired only as a result of calculation, but the dependence of current density on the potential variable on the boundary is given). That is why I need to assign a variable (for example, 'v') to still uncalculated potential distribution on the plate boundary, so I can define a variable to current density j=f(v) in the section “definition->function”.

Do you have any ideas how to put this into life? I guess we should use “probe” here, but I don’t know how and if it’s going to work.
Thank you for quick response, Ivar. But the thing is that I don’t have to define the function T(z), as it is unknown in the very beginning – it can be acquired only as a result of calculation. I have to assign a variable to the still uncalculated temperature distribution on the element boundary. And then I'd like to use this variable for another function in a section (definition --> function), which depends on it. Here is an example from another physics field: We have a diod (2 parallel plates). I need to define the current density as a function of potential distribution on the plate boundary (this potential is initially unknown, as it can be acquired only as a result of calculation, but the dependence of current density on the potential variable on the boundary is given). That is why I need to assign a variable (for example, 'v') to still uncalculated potential distribution on the plate boundary, so I can define a variable to current density j=f(v) in the section “definition->function”. Do you have any ideas how to put this into life? I guess we should use “probe” here, but I don’t know how and if it’s going to work.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 28.09.2011, 14:49 GMT-4
Hi

A constant Temperature boundary is to allow COMSOL to calculate the heat flux through the boundary such that the temperature is as desired.

So, if you do not know the temperature, you must know something about the heat flux/exchange to allow COMSOL to estimate the Temperature

It's one ot the other,for me

--
Good luck
Ivar
Hi A constant Temperature boundary is to allow COMSOL to calculate the heat flux through the boundary such that the temperature is as desired. So, if you do not know the temperature, you must know something about the heat flux/exchange to allow COMSOL to estimate the Temperature It's one ot the other,for me -- Good luck Ivar
Mikhail Polous
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 29.09.2011, 03:10 GMT-4
Hi, Ivar.
It is clear, that I need to know the value of T or flux/exchange on the boundary, but I have a vague situation over here: I know a flux that is dependent on the T at the boundary of the element... That is why at first I want to assign a variable to a still unknown T on the element boundary, and then to put flux by means of this variable. That is the thing I don't know how to do.. any ideas? :)
Hi, Ivar. It is clear, that I need to know the value of T or flux/exchange on the boundary, but I have a vague situation over here: I know a flux that is dependent on the T at the boundary of the element... That is why at first I want to assign a variable to a still unknown T on the element boundary, and then to put flux by means of this variable. That is the thing I don't know how to do.. any ideas? :)

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content