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Old   July 3, 2012, 08:09
Default buoyantBoussinesqSimpleFoam
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Primoz Ternik
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Hi,

using the buoyantBoussinesqSimpleFoam (in Open Foam 2.1.1) I am trying to solve the laminar Rayleigh-Benard convection (laminar natural convection in a square cavity heated from bellow) for Pr=10 and Ra=1e05. I have set up the case, run the solver...

Unfortunately, results for the dimensionless temperature and horizontal velocity along the vertical mid-plane (i.e. along x/L=0.50) are "not good"! They are compared with the results of

O. Turan, N. Chakraborty, R.J. Poole (2012). Laminar Rayleigh-Benard convection of yield stress fluids in a square enclosure, Journal of Non-Newtonian Fluid Mechanics, Vol. 171-172, p. 83-96

and with the results obtained with "commercial" code!

Can someone please check if I have done any obvious mistakes in setting up the case or is the problem with the solver??

In addition, I have the following question. Why is it necessary to have the following files (required for a turbulent flow) in a 0 directory - alphat, epsilon, k, kappat, nut??? If I run the case without these files (in a 0 directory) I get the following message:

--> FOAM FATAL IO ERROR:
cannot find file

file: /home/ternik/OpenFOAM/ternik-2.1.1/Cavity_RayleighBenard/0/kappat at line 0.

From function regIOobject::readStream()
in file db/regIOobject/regIOobjectRead.C at line 73.

FOAM exiting


Cheers,
Primoz
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File Type: png Temperature.png (5.6 KB, 69 views)
File Type: png Velocity.png (5.7 KB, 54 views)
Attached Files
File Type: gz Cavity_RayleighBenard.tar.gz (4.0 KB, 35 views)
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Old   July 3, 2012, 10:09
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Anton Kidess
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They have a non-Newtonian fluid - you don't.
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Old   July 3, 2012, 11:10
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Quote:
Originally Posted by akidess View Post
They have a non-Newtonian fluid - you don't.
Yes, they do. But the results are compared for the "newtonian case"...
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Old   July 6, 2012, 09:09
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Quote:
Originally Posted by ternik View Post
Yes, they do. But the results are compared for the "newtonian case"...
Dear Foamers,

is there anybody willing to help (assist) to correctly set up and solve this "test case"!?

i think we will all benefit from this...

Enjoy,
Primoz
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Old   July 6, 2012, 10:25
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Dear Primoz,

can you evaluate the attached modified case? I think convergence is much better and at a first glance results look fine...

I think the most important change is the relaxation factor for p_rgh.

Martin
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Old   July 7, 2012, 17:50
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Quote:
Originally Posted by MartinB View Post
Dear Primoz,

can you evaluate the attached modified case? I think convergence is much better and at a first glance results look fine...

I think the most important change is the relaxation factor for p_rgh.

Martin
Dear Martin,

thanks a lot for your tip(s). i have run your case and although that the convergence is much better the results are still not O.K.! As a matter of fact they are similar to the one I have presented in my original post.

Since te velocity field is almost zero, I have started to question the boundary conditions for the pressure (especially for p_rgh). What do you think? If you will find time, please check this link

https://unihub.ru/tools/ofservice/br.../buoyantCavity

and associated b.c. for the pressure.

All the best,
Primoz
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