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Override not-applicable boundary
Posted Apr 30, 2013, 6:42 p.m. EDT 3 Replies
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Hi,
This may be easy but I don't see how to do it in V4.3a. In V3.5a it was not hard. I would like to apply convective cooling at an interior boundary in my model.
Currently, all the interior boundaries are listed as not-applicable.
How do I override the not-applicable boundary in order to apply a convective film there?
Thanks,
Art
This may be easy but I don't see how to do it in V4.3a. In V3.5a it was not hard. I would like to apply convective cooling at an interior boundary in my model.
Currently, all the interior boundaries are listed as not-applicable.
How do I override the not-applicable boundary in order to apply a convective film there?
Thanks,
Art
Attachments:
3 Replies Last Post May 1, 2013, 2:32 p.m. EDT
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Posted:
1 decade ago
Hi
I believe because it's not considered "physical" to have "convective cooling" at an internal interface. Where does that heat go ? to a constant T sink in the middle of the material ?
In V4 you must use a boundary Heat Source node to exchange explicitly on an internal boundary, so you can too, as in v3.5 have internal convection.
Use the Options preferences show equation view to analyse the internal equations COMSOL uses for the different boundary nodes
--
Good luck
Ivar
I believe because it's not considered "physical" to have "convective cooling" at an internal interface. Where does that heat go ? to a constant T sink in the middle of the material ?
In V4 you must use a boundary Heat Source node to exchange explicitly on an internal boundary, so you can too, as in v3.5 have internal convection.
Use the Options preferences show equation view to analyse the internal equations COMSOL uses for the different boundary nodes
--
Good luck
Ivar
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Posted:
1 decade ago
Hi Ivar,
Thanks for your comments. As they say, a picture is worth a thousand words. Please see attached picture.
The strip is assigned an AC voltage and causing the tissue to heat. What I am modeling is the effect of fluid flow cooling the tissue where the spiral, electrically conductive strip contacts the tissue.
The inlet side on the left is where the fluid enters. The outlets are 8 small holes on the balloon which is in contact with the tissue.
In the two cases that I tried to do, simple forced convection and also fluid flow, Comsol does not allow me to assign the balloon holes as outlets. As I said in my earlier post, in the convection model, Comsol does not allow me to assign the boundary between the balloon and tissue as the convective source.
I am not sure how to implement the suggestions that you made in you reply. Could you please explain further?
Thanks,
Art
Thanks for your comments. As they say, a picture is worth a thousand words. Please see attached picture.
The strip is assigned an AC voltage and causing the tissue to heat. What I am modeling is the effect of fluid flow cooling the tissue where the spiral, electrically conductive strip contacts the tissue.
The inlet side on the left is where the fluid enters. The outlets are 8 small holes on the balloon which is in contact with the tissue.
In the two cases that I tried to do, simple forced convection and also fluid flow, Comsol does not allow me to assign the balloon holes as outlets. As I said in my earlier post, in the convection model, Comsol does not allow me to assign the boundary between the balloon and tissue as the convective source.
I am not sure how to implement the suggestions that you made in you reply. Could you please explain further?
Thanks,
Art
Attachments:
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Posted:
1 decade ago
Hi
Again an inlet and outlet, are normally only definable as external boundaries, otherwise you do not respect the conservation of mass and energy. So you need an "external" outlet somewhere, or you want to pressurise your "ballon"
Normally if you have fluid flow and HT your convection is taken into account by the Navier-Stokes and the HT, you ue convective colling boundaries to mimic all the NS calculations and use simple linear equations instead. Mostly well sufficient
To get your model up, when mixing many physics, it's worth to sketc out all dependent variables and the main BC conditions (one per degree of derivatives in the PDE to ensure you respect them all, including all hypothesis: conservation laws ...
--
Good luck
Ivar
Again an inlet and outlet, are normally only definable as external boundaries, otherwise you do not respect the conservation of mass and energy. So you need an "external" outlet somewhere, or you want to pressurise your "ballon"
Normally if you have fluid flow and HT your convection is taken into account by the Navier-Stokes and the HT, you ue convective colling boundaries to mimic all the NS calculations and use simple linear equations instead. Mostly well sufficient
To get your model up, when mixing many physics, it's worth to sketc out all dependent variables and the main BC conditions (one per degree of derivatives in the PDE to ensure you respect them all, including all hypothesis: conservation laws ...
--
Good luck
Ivar