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 The information provided may be out of date.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.
calculate the heat flux difference across a boundary using up and down operator ?
Posted 31 gen 2011, 23:25 GMT-5 Parameters, Variables, & Functions Version 4.0 12 Replies
Please login with a confirmed email address before reporting spam
there are two domains, domain 1 and domain 2, they are connected with each other through boundary 1.
the heat flux across the boundary 1 is discontinuous (for example, flux1 in domain 1, flux2 in domain 2, flux1>flux2), and I want to get the difference between these two fluxes.
I read the user's guide, and find that the operators "up", "down" can make it, which one should I use? and I don't know how to use these two operators even after reading the user's guide.
the space dimension is just 1D
Can anybody give me an example?
Thank you!
the heat flux across the boundary 1 is discontinuous (for example, flux1 in domain 1, flux2 in domain 2, flux1>flux2), and I want to get the difference between these two fluxes.
I read the user's guide, and find that the operators "up", "down" can make it, which one should I use? and I don't know how to use these two operators even after reading the user's guide.
the space dimension is just 1D
Can anybody give me an example?
Thank you!
12 Replies Last Post 5 feb 2011, 02:22 GMT-5
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
by default (Finish Union mode) two adjacent boundaries have "continuity" BC between them. You need to select the Assembly mode (+create imprints) and use the Selection list to identify the correct boundary (switch back to geometry mode to see the numbering w.r.t. geometrical objects)
Then you need to define the physics on your boundary to link the discontinuity somehow, and then you have access to the up down. Note the number id of the boundaries appear on the "down/inward side.
Have you tried the coordinate plotting under: Results - Plot Group - More ...
--
Good luck
Ivar
by default (Finish Union mode) two adjacent boundaries have "continuity" BC between them. You need to select the Assembly mode (+create imprints) and use the Selection list to identify the correct boundary (switch back to geometry mode to see the numbering w.r.t. geometrical objects)
Then you need to define the physics on your boundary to link the discontinuity somehow, and then you have access to the up down. Note the number id of the boundaries appear on the "down/inward side.
Have you tried the coordinate plotting under: Results - Plot Group - More ...
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
by default (Finish Union mode) two adjacent boundaries have "continuity" BC between them. You need to select the Assembly mode (+create imprints) and use the Selection list to identify the correct boundary (switch back to geometry mode to see the numbering w.r.t. geometrical objects)
Then you need to define the physics on your boundary to link the discontinuity somehow, and then you have access to the up down. Note the number id of the boundaries appear on the "down/inward side.
Have you tried the coordinate plotting under: Results - Plot Group - More ...
--
Good luck
Ivar
Hi, Ivar, thank you!
I still have questions.
1)"use the Selection list to identify the correct boundary", how to do it? Create a Selection under Definition, and choose the boundary?
2) "define the physics on your boundary to link the discontinuity", what is define the physics on boundary? Is that mean set the boundary condition?
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
you have the selection list window see the small arrow "v" on the first GUI border. This window gives you the list of the ids for the different items, it changes by selecting geoemtry (Objects) or entities (domains, boundaries, edges or points in the view border of the graphics window). This is very usefull for selecting items when you have many, and t sort out the "left and right" or up/down boundaries whith assembly mode on.
then by default interiour domains in "union" modes implies continuity of flux across the boundary. When you use assembly mdoe, there is no default coupling (isolation) between the adjacent boundaries, you must specify thenm expliitely, this means you can add isolation surfaces with your own physics not respecting the continuity of flux (but still respecting phyiscs and PDE in general to allow COMSOL to solve the issue
--
Good luck
Ivar
you have the selection list window see the small arrow "v" on the first GUI border. This window gives you the list of the ids for the different items, it changes by selecting geoemtry (Objects) or entities (domains, boundaries, edges or points in the view border of the graphics window). This is very usefull for selecting items when you have many, and t sort out the "left and right" or up/down boundaries whith assembly mode on.
then by default interiour domains in "union" modes implies continuity of flux across the boundary. When you use assembly mdoe, there is no default coupling (isolation) between the adjacent boundaries, you must specify thenm expliitely, this means you can add isolation surfaces with your own physics not respecting the continuity of flux (but still respecting phyiscs and PDE in general to allow COMSOL to solve the issue
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
you have the selection list window see the small arrow "v" on the first GUI border. This window gives you the list of the ids for the different items, it changes by selecting geoemtry (Objects) or entities (domains, boundaries, edges or points in the view border of the graphics window). This is very usefull for selecting items when you have many, and t sort out the "left and right" or up/down boundaries whith assembly mode on.
then by default interiour domains in "union" modes implies continuity of flux across the boundary. When you use assembly mdoe, there is no default coupling (isolation) between the adjacent boundaries, you must specify thenm expliitely, this means you can add isolation surfaces with your own physics not respecting the continuity of flux (but still respecting phyiscs and PDE in general to allow COMSOL to solve the issue
--
Good luck
Ivar
Hi, Ivar, thank you very much
What is "isolation surface"? How to add isolation surfaces with my own physics on the adjacent boundaries?
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
check the doc and the model for "thin film resistor" case, or look for boundary physics. In COMSOL you can simulate a thin layer as a boundary property to avoid to mesh it in the thickness (assuming you have a constant gradient in the thickness direction
--
Good luck
Ivar
check the doc and the model for "thin film resistor" case, or look for boundary physics. In COMSOL you can simulate a thin layer as a boundary property to avoid to mesh it in the thickness (assuming you have a constant gradient in the thickness direction
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
check the doc and the model for "thin film resistor" case, or look for boundary physics. In COMSOL you can simulate a thin layer as a boundary property to avoid to mesh it in the thickness (assuming you have a constant gradient in the thickness direction
--
Good luck
Ivar
Thank you, Ivar!
I cannot find the model for "thin film resistor" in the Model Library, my comsol verion is 4
where is it? Thank you!
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
if you have 4.0 it's probably not yet in there, I believe its in 4.1 (certainly 3.5) Have you tried a model library update ? but it could be only available in the current 4.1 not sure, no access any longer to 4.0
--
Good luck
Ivar
if you have 4.0 it's probably not yet in there, I believe its in 4.1 (certainly 3.5) Have you tried a model library update ? but it could be only available in the current 4.1 not sure, no access any longer to 4.0
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
if you have 4.0 it's probably not yet in there, I believe its in 4.1 (certainly 3.5) Have you tried a model library update ? but it could be only available in the current 4.1 not sure, no access any longer to 4.0
--
Good luck
Ivar
Okay, thank you, Ivar!
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
by default (Finish Union mode) two adjacent boundaries have "continuity" BC between them. You need to select the Assembly mode (+create imprints) and use the Selection list to identify the correct boundary (switch back to geometry mode to see the numbering w.r.t. geometrical objects)
Then you need to define the physics on your boundary to link the discontinuity somehow, and then you have access to the up down. Note the number id of the boundaries appear on the "down/inward side.
Have you tried the coordinate plotting under: Results - Plot Group - More ...
--
Good luck
Ivar
Thank you, Ivar
"down/up" can only be used in "Assembly mode"?
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
on internal boundaries yes, as what is up down on internal boundaries ?
I just got stuck myself in one of those collisions/limitations ;)
--
Good luck
Ivar
on internal boundaries yes, as what is up down on internal boundaries ?
I just got stuck myself in one of those collisions/limitations ;)
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
on internal boundaries yes, as what is up down on internal boundaries ?
I just got stuck myself in one of those collisions/limitations ;)
--
Good luck
Ivar
Hi, Ivar, thank you!
About the internal boundary, If I create a rectangle, and then add a line at the center of this rectangle to separate it into two new rectangles, does comsol regard this line as the internal boundary by default? or I need to do something to make comsol think this line as a internal boundary?
Thank you!
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
yes if:
- the line is going cleanly from one boundary to the next
- you are in "Finish Union"
but you will not notice it before you re in th ematerial section, and you ask for the "selection view"
you can obtain the same effect inside the geoemtry section by doing an "union" and then a split
--
Good luck
Ivar
yes if:
- the line is going cleanly from one boundary to the next
- you are in "Finish Union"
but you will not notice it before you re in th ematerial section, and you ask for the "selection view"
you can obtain the same effect inside the geoemtry section by doing an "union" and then a split
--
Good luck
Ivar