pressure correction or mesh quality

michel2008 · February 7, 2013, 06:47

Dear all,

I am trying to simulate laminar flow in micro-cylinders embedded in a rectangular microchannel so I simplified the model with a unit cell which is a square microchannel including a micro-cylinder with an inlet and outlet by apply periodic boundary condition in the inlet and outlet (I used mass-flow rate for inlet boundary condition).
The point is when I applied periodic boundary condition in Fluent, an error just appeared before the first iteration calculating solution "divergence detected in AMG solver-pressure correction" . Although I tried to overcome this problem by reducing under relaxation factor and change some parameters in solution control, unfortunately I could not be able to solve it.
In the other hand when I want to make periodic region in inlet and outlet in mesh utility, but the coordinate system light yellow prevent to well define it.

I suggest maybe it is related to mesh quality and i have to make a finer mesh, do you have any suggestion about the mesh or solving this problem.
Any help would be greatly appreciated.

Regards
Michel

mrenergy · February 7, 2013, 07:28

Hi michel

I think it is not mesh quality related problem ... the convergence happens before the solution at all ...

It seems to be a problem in the boundary conditions ...
review ALL your boundary conditions CAREFULLY, and check that is physically consistent and acceptable.

GOOD LUCK

Mamdouh

michel2008 · February 7, 2013, 10:57

Dear Mamdouh

Thanks for your reply.

I have checked and it seems there is not anything wrong in boundary condition. But when I tried to change to a finer mesh, the solution give me the same error after 2 iteration. Do you think this problem would be solved with a special mesh or you have any idea about it?

Regards
Michel

February 7, 2013, 06:47	pressure correction or mesh quality	#1
michel2008 New Member michel Join Date: Nov 2012 Posts: 7 Rep Power: 13	Dear all, I am trying to simulate laminar flow in micro-cylinders embedded in a rectangular microchannel so I simplified the model with a unit cell which is a square microchannel including a micro-cylinder with an inlet and outlet by apply periodic boundary condition in the inlet and outlet (I used mass-flow rate for inlet boundary condition). The point is when I applied periodic boundary condition in Fluent, an error just appeared before the first iteration calculating solution "divergence detected in AMG solver-pressure correction" . Although I tried to overcome this problem by reducing under relaxation factor and change some parameters in solution control, unfortunately I could not be able to solve it. In the other hand when I want to make periodic region in inlet and outlet in mesh utility, but the coordinate system light yellow prevent to well define it. I suggest maybe it is related to mesh quality and i have to make a finer mesh, do you have any suggestion about the mesh or solving this problem. Any help would be greatly appreciated. Regards Michel

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February 7, 2013, 07:28		#2
mrenergy Member Mamdouh Join Date: Dec 2012 Location: Calgary, Alberta, Canada Posts: 39 Rep Power: 13	Hi michel I think it is not mesh quality related problem ... the convergence happens before the solution at all ... It seems to be a problem in the boundary conditions ... review ALL your boundary conditions CAREFULLY, and check that is physically consistent and acceptable. GOOD LUCK Mamdouh

February 7, 2013, 10:57		#3
michel2008 New Member michel Join Date: Nov 2012 Posts: 7 Rep Power: 13	Dear Mamdouh Thanks for your reply. I have checked and it seems there is not anything wrong in boundary condition. But when I tried to change to a finer mesh, the solution give me the same error after 2 iteration. Do you think this problem would be solved with a special mesh or you have any idea about it? Regards Michel