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Heat equation in cylindrical coordinate

Posted 22 avr. 2013, 10:52 UTC−4 Heat Transfer & Phase Change Version 4.2a, Version 4.3a 8 Replies

Ruzbeh
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Hi
Does any one know how I can use cylindrical coordinate in 2D (r &theta) in heat trasnfer module for the heat equation? Basically I want to monitor conduction in radial direction only.

Thanks
8 Replies Last Post 26 avr. 2013, 02:26 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 22 avr. 2013, 11:49 UTC−4
Hi

COMSOL solves in cartesian coordinates, but you can easily plot out in other systems, either by defining a local user coordinate system (Model - definition coordinate systems ...) and then refer to the sys2.r sys2.phi or whatever "n" in case of severalcoordinate systems.

Or you just define a variable my_R = sqrt((x-x0)^2+(y-y0)^2) and my_phi = atan2((y.y0),(x-x0))
where x0,y0 is the centre of your cylindrical coordinate (it might be 0,0 hence so much simpler ;)

--
Good luck
Ivar
Hi COMSOL solves in cartesian coordinates, but you can easily plot out in other systems, either by defining a local user coordinate system (Model - definition coordinate systems ...) and then refer to the sys2.r sys2.phi or whatever "n" in case of severalcoordinate systems. Or you just define a variable my_R = sqrt((x-x0)^2+(y-y0)^2) and my_phi = atan2((y.y0),(x-x0)) where x0,y0 is the centre of your cylindrical coordinate (it might be 0,0 hence so much simpler ;) -- Good luck Ivar
Ruzbeh
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Posted: 1 decade ago 22 avr. 2013, 12:31 UTC−4
Hi Ivar

Thanks for the reply. I am trying to switch off conduction around the circumferential direction by altering the heat equation. Being in cartesian corrdinate, heat equation has made the life more difficult for me. Is it possible?
Hi Ivar Thanks for the reply. I am trying to switch off conduction around the circumferential direction by altering the heat equation. Being in cartesian corrdinate, heat equation has made the life more difficult for me. Is it possible?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 23 avr. 2013, 04:47 UTC−4
Hi

have you tried to use anisotropic material definitions, and set the main physics node to use your cylindrical coordinate ?

use the get initial values and plot coordinate systems to check the orientations

--
Good luck
Ivar
Hi have you tried to use anisotropic material definitions, and set the main physics node to use your cylindrical coordinate ? use the get initial values and plot coordinate systems to check the orientations -- Good luck Ivar
Ruzbeh
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Posted: 1 decade ago 23 avr. 2013, 06:27 UTC−4
Hi

I have changed the coordinate system from global to cylindrical in the heat transfer node. It changes the anisotropic thermal conductivity according to the cylindrical coordinate. Still trying to work out how I can switch conduction around the circumference.

Thanks
Syed
Hi I have changed the coordinate system from global to cylindrical in the heat transfer node. It changes the anisotropic thermal conductivity according to the cylindrical coordinate. Still trying to work out how I can switch conduction around the circumference. Thanks Syed
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 23 avr. 2013, 07:07 UTC−4
Hi

I'm not sure I fully understand what you are trying, a drawing or a model could make it easier to catch ;)

--
Good luck
Ivar
Hi I'm not sure I fully understand what you are trying, a drawing or a model could make it easier to catch ;) -- Good luck Ivar
Ruzbeh
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Posted: 1 decade ago 23 avr. 2013, 07:25 UTC−4
hi

Please find attached the drawing of my model. It is just a simple ring. What I am trying is to look at the heat conduction only in radial direction by turning of tangential heat condcution. I have a coupled sturcutal mechanics module with my model. The structural part is not the problem. It is the heat equation I am trying to configure.

Could you please explain what these means:

sys2.T11
sys2.T12 etc..

my dependent variable is T for heat transfer part. If I switch the coordinate to cylindrical the conductivy changes like this:

e.g.: k*(sys2.T11^2+sys2.T21^2+sys2.T31^2)

I am assuming these are coverting k in cylindrical coordinates.
hi Please find attached the drawing of my model. It is just a simple ring. What I am trying is to look at the heat conduction only in radial direction by turning of tangential heat condcution. I have a coupled sturcutal mechanics module with my model. The structural part is not the problem. It is the heat equation I am trying to configure. Could you please explain what these means: sys2.T11 sys2.T12 etc.. my dependent variable is T for heat transfer part. If I switch the coordinate to cylindrical the conductivy changes like this: e.g.: k*(sys2.T11^2+sys2.T21^2+sys2.T31^2) I am assuming these are coverting k in cylindrical coordinates.

Attachments:

Ruzbeh
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Posted: 1 decade ago 24 avr. 2013, 08:47 UTC−4
Still unable to determine heat conduction only in angular/tangential direction. Any suggestions?
Still unable to determine heat conduction only in angular/tangential direction. Any suggestions?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 26 avr. 2013, 02:26 UTC−4
Hi

if you have a simple ring, then you can define a cylindrical coordinate system at the ring centre (Model - Definition Coordinate systems - Cylindrical coordinates) if this is then sys2, you have access to sys2.r (=sqrt((x-x0)^2+(y-yo)^2) if the axis is along Z, and x0,y0 are the centre offset) and to sys2.phi (=atan2(y,x) the angular variable hypotheses as before) and to sys2.z which is as Z

the boundary conditions sys1.n is the normal ,while t1 and t2 are the two tangents vectors, but they are not always easy to orient, as COMSOL decides where and how

--
Good luck
Ivar
Hi if you have a simple ring, then you can define a cylindrical coordinate system at the ring centre (Model - Definition Coordinate systems - Cylindrical coordinates) if this is then sys2, you have access to sys2.r (=sqrt((x-x0)^2+(y-yo)^2) if the axis is along Z, and x0,y0 are the centre offset) and to sys2.phi (=atan2(y,x) the angular variable hypotheses as before) and to sys2.z which is as Z the boundary conditions sys1.n is the normal ,while t1 and t2 are the two tangents vectors, but they are not always easy to orient, as COMSOL decides where and how -- Good luck Ivar

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