High Courant No. Issue.

ajwad.turjo · March 17, 2023, 02:39

Hi,
I am running a blood flow simulation using pulsatile BC. My Courant No. gets high up to 100+. I am using pisoFoam and the simulation does not crash. But I am confused about the reliability of the results. Is it normal to have such high Co. in blood flow simulation?

I am using a timestep size of 0.5e-4. My whole domain is (0.023 x 0.012 x 0.009 m) and mesh size is 0.5e-3 m. I am meshing with cfMesh 1.1 and for this sizing Co gets high up to 20. There are some small cells which are making such high Co. No.

Although my simulation keeps running, how can I control my Co no.?
Should I worry about such high Co? Or just proceed to my next simulation?

Thank you.

jenc24 · March 19, 2023, 13:29

You can control your Co number by enabling adjustTimeStep an setting maxCo in your controlDict.

Is it possible you have set nOuterCorrectors > 1? If so, your solver is actually running in PIMPLE mode, which can run with higher Co numbers.

March 17, 2023, 02:39	High Courant No. Issue.	#1
ajwad.turjo New Member Md. Ajwad Mohimin Join Date: Jul 2020 Posts: 1 Rep Power: 0	Hi, I am running a blood flow simulation using pulsatile BC. My Courant No. gets high up to 100+. I am using pisoFoam and the simulation does not crash. But I am confused about the reliability of the results. Is it normal to have such high Co. in blood flow simulation? I am using a timestep size of 0.5e-4. My whole domain is (0.023 x 0.012 x 0.009 m) and mesh size is 0.5e-3 m. I am meshing with cfMesh 1.1 and for this sizing Co gets high up to 20. There are some small cells which are making such high Co. No. Although my simulation keeps running, how can I control my Co no.? Should I worry about such high Co? Or just proceed to my next simulation? Thank you.

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March 19, 2023, 13:29		#2
jenc24 New Member Join Date: Nov 2022 Location: Slovenia Posts: 12 Rep Power: 4	You can control your Co number by enabling adjustTimeStep an setting maxCo in your controlDict. Is it possible you have set nOuterCorrectors > 1? If so, your solver is actually running in PIMPLE mode, which can run with higher Co numbers.