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Why is the result non-symmetric

Posted Feb 4, 2015, 12:41 p.m. EST Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 5.0 1 Reply

John
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Hi, I made a small change to a bouyancy model online, basically to create a geometry that I thought would be symmetric - along y=0 I put a cold blob on one side and a warm blob on the other side. The COMSOL formulation is using the Boussinesq approximation which (I thought) was "reversible".

But looking at the results, the velocity and temperature are not close to being symmetric. Any thoughts?
1 Reply Last Post Feb 4, 2015, 12:51 p.m. EST
John
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Posted: 9 years ago Feb 4, 2015, 12:51 p.m. EST
Aha. Apparently all I have to do is post and immediately I understand my problem... Please ignore the post.

I now realize that because of the effective "rigidity" of the bounding domain, the cold fluid puts downward pressure on that part of the boundary near the cold blob whereas there is no similarly symmetric response from the warm blob - it just goes up in impeded. So the problem is not symmetric. So neither is the answer.

Oh well. I learned something today :-)


Hi, I made a small change to a bouyancy model online, basically to create a geometry that I thought would be symmetric - along y=0 I put a cold blob on one side and a warm blob on the other side. The COMSOL formulation is using the Boussinesq approximation which (I thought) was "reversible".

But looking at the results, the velocity and temperature are not close to being symmetric. Any thoughts?


Aha. Apparently all I have to do is post and immediately I understand my problem... Please ignore the post. I now realize that because of the effective "rigidity" of the bounding domain, the cold fluid puts downward pressure on that part of the boundary near the cold blob whereas there is no similarly symmetric response from the warm blob - it just goes up in impeded. So the problem is not symmetric. So neither is the answer. Oh well. I learned something today :-) [QUOTE] Hi, I made a small change to a bouyancy model online, basically to create a geometry that I thought would be symmetric - along y=0 I put a cold blob on one side and a warm blob on the other side. The COMSOL formulation is using the Boussinesq approximation which (I thought) was "reversible". But looking at the results, the velocity and temperature are not close to being symmetric. Any thoughts? [/QUOTE]

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