FVM code diverge when the gravity is included

k.gonski · June 12, 2018, 22:09

Hi All,

I have an in-house code which is based on FVM for incompressible flows. I used it to solve liquid flow in a vertical pipe. The code was working if the gravity was omitted or not considered. The inclusion of the gravity led to the divergence of the code.

I tested the code based on the codes from Ferziger and Peric's book. The same problem occurred.

I would appreciate that you could suggest how to solve this problem.

Regards,
Gonski

FMDenaro · June 13, 2018, 03:06

Quote:

Originally Posted by k.gonski

Hi All,

I have an in-house code which is based on FVM for incompressible flows. I used it to solve liquid flow in a vertical pipe. The code was working if the gravity was omitted or not considered. The inclusion of the gravity led to the divergence of the code.

I tested the code based on the codes from Ferziger and Peric's book. The same problem occurred.

I would appreciate that you could suggest how to solve this problem.

Regards,
Gonski

Assuming you are using the Bousinnesq model, I can think about a numerical instability, a source term change the constraint on the time step. Have you tried to use a smaller dt?

k.gonski · June 14, 2018, 09:53

I am not using Bousinnesq. My specific case needs the explicit consideration of gravity. Also, I solved a steady problem.

Eifoehn4 · June 19, 2018, 02:09

It would be helpful, if you can give us some more details about the implementation.

k.gonski · June 21, 2018, 22:03

Quote:

Originally Posted by Eifoehn4

It would be helpful, if you can give us some more details about the implementation.

My implementation is as below:

the gravity (density*acceleration) was added as the source term into the momentum equations. There are no other treatments. For gas flow, the solution is ok. But for liquid flow, the code blew up rapidly.

June 12, 2018, 22:09	FVM code diverge when the gravity is included	#1
k.gonski New Member Gonski Join Date: Jun 2018 Posts: 3 Rep Power: 7	Hi All, I have an in-house code which is based on FVM for incompressible flows. I used it to solve liquid flow in a vertical pipe. The code was working if the gravity was omitted or not considered. The inclusion of the gravity led to the divergence of the code. I tested the code based on the codes from Ferziger and Peric's book. The same problem occurred. I would appreciate that you could suggest how to solve this problem. Regards, Gonski

June 19, 2018, 02:09		#4
Eifoehn4 Senior Member - Join Date: Jul 2012 Location: Germany Posts: 184 Rep Power: 13	It would be helpful, if you can give us some more details about the implementation. __________________ Check out my side project: A multiphysics discontinuous Galerkin framework: Youtube, Gitlab.

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June 14, 2018, 09:53		#3
k.gonski New Member Gonski Join Date: Jun 2018 Posts: 3 Rep Power: 7	I am not using Bousinnesq. My specific case needs the explicit consideration of gravity. Also, I solved a steady problem.