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September 1, 2010, 08:17 |
Courant numer
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#1 |
Member
Ovidiu Michiu
Join Date: Apr 2010
Location: Munich, Germany
Posts: 53
Rep Power: 15 |
Hello,
I'm trying to do my first case in OF. I converted a mesh from fluent, an airfoil 2D, compressible flow with M=0.8, Spalart-Allmaras imposed and a Courant Numner=200 in fluent. I adapt an compressible case from tutorials of OF, /sonicFoam/RAS/naca. I can see the mesh without any problems, but I don't know how can I calculate the time step, delta t from /system/controlDict. The second problem regards the thermophysicalProperties definition. I read the tutorial but when i started to write my thermophysicalPropoperties i got stuck; I have sutherland law imposed and perfect gas; how can i calculate all the coefficients to have a good thermoProp correct? Thk, Best Regards, Ovidiu |
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September 1, 2010, 10:50 |
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#2 |
Senior Member
Join Date: Aug 2010
Location: Groningen, The Netherlands
Posts: 216
Rep Power: 18 |
The courant number is defined like this:
C = (U * delta t) / delta x with U = velocity of the liquid/ moving wall what ever delta t you want to calculate and delta x = domain length [m] / Number of Elements in x direction for more details see here: http://www.openfoam.com/docs/user/cavity.php chapter 2.1.1.4 Control It happens to be the first tutorial..... |
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September 1, 2010, 11:42 |
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#3 |
Member
Ovidiu Michiu
Join Date: Apr 2010
Location: Munich, Germany
Posts: 53
Rep Power: 15 |
thk colinB,
i check the tutorial before posting the thread. the problem is that i don't know the cell size, delta x. i receive the mesh from fluent, i didn't do the mesh and i don't have fluent install on my pc to see the cell mesh. Best, Ovidiu |
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September 2, 2010, 04:25 |
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#4 |
Senior Member
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 29 |
After conversion you can run checkMesh, and then get information about cell volumes. For a rough estimate of the Courant number you can take the third root of the cell volume.
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September 3, 2010, 11:55 |
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#5 | |
Member
Sabin Ceuca
Join Date: Mar 2010
Location: Munich
Posts: 42
Rep Power: 15 |
Quote:
you can actually plot the cell Volumes using the variable mesh.V() and then compute the dx you like best Ciao, Sabin |
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