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Solver asking for variables in domain it is not supposed to solve for in Nonisothermal Flow
Posted Oct 6, 2019, 6:45 p.m. EDT Version 5.4 3 Replies
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Hi all!
I have been working on a model for a while now and keep getting the same kind of errors over and over. It is probably a stupid mistake, as I am a novice in COMSOL (as a student), but I cannot figure it out.
In my model, there are two steps, one for computing a turbulent flow through one domain and one for computing the heat flow through the entire model, as well as convection in one domain that has no initial flow (but is seperated from the other domain). I have included a picture of the problem to this post, as well as a .mph file of my model.
The model is perfectly able to compute the step for the turbulent flow. However, it keeps failing on the second step computing the heat flow. In the second study step, it gives an error that says that the Nonisothermal Flow interface that has the turbulent flow interface (over domain 5) selected for Fuid Flow under Coupled Interfaces, lacks a velocity component in a domain it is not even supposed to solve for (domain 8). I included a picture of the error to this post (Error_Domer.png).
To try and counteract the error, I tried to first have the model solve for a Laminar Flow in the domain the Nonisothermal Flow is asking for, but it seems unable to solve for a stationary domain which should display no flow, or zero velocity (Error_Domer_2.png).
Can anyone pinpoint what is going wrong?
All help is welcome. Thank you in advance!
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For anyone with the same problem, now or in the future, defining a second Fluid in the the Heat Transfer interface and choosing the correct inputs for T, p_A and velocity u solves the problem.
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Hi,
A workaround is nice, but it's better to understand what is wrong.
And as you pointed out "u" is not defined on domain "8" so COMSOL should not even try it. But looking at the COMSOL "equation view" of "nitf3" I see that u,v,w, and p (and even T) are flagged as "Global" while I believe they should be restricted to the domain "5" in your case.
This could be a bug within COMSOL, so I would strongly suggest that you report this to COMSOL Support and have them identify why. As this could then lead to a bug fix that would help us all. With the X thousand equations under the hood of COMSOL one newer know what subtile error is intruduces by adding in a "quick work round".
Sincerely Ivar
-------------------Have fun COMSOLing,
Sincerely,
Ivar
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Hi Ivar,
Thank you for pointing that out! I appreciate the fact that you dug into the problem after it was solved, for the sake of improving the software for all users.
I was not aware of the fact that this could be a problem that could've arised 'under the hood'. The solution was given to me by the COMSOL support, but I will forward your idea of the possibility of this being a bug to them.
Kind regards, Maarten