Increasing Courant Number OpenFoam

Battousai07 · May 26, 2020, 16:07

Hi. I am working on a nonuniform, curved vessel. I need to solve the case in laminar transient which i've used pimpleFoam and icoFoam so far. The Courant number continiues to increase. I have tried adjustable time step and defined maxCo as 5 so far. This satisfies the condition but time step continiues to decrease very low values to make the condition satisfied. My mesh is OK in terms of skewness and orthogonatily. What can cause this problem?

geth03 · May 27, 2020, 04:34

does the solver crash or does it run really slow with high CFL number?

Battousai07 · May 27, 2020, 06:33

Runs with high CFL number. First it was crashing but i have managed to prevent that by introducing nonOrthogonal correctors and nCorrectors

geth03 · May 28, 2020, 03:03

can you output the courant number for your domain and analyze it with paraview? there is a function for that, which you need to write in controlDict.
you can then see where your CFL number is relatively high.

also execute checkMesh and check if a new directory is created in polyMesh-directory. if your mesh is broken somewhere the directory will be created.
you can then create vtk-files and open it with paraview, so your problematic areas will be highlighted.

HPE · May 28, 2020, 17:28

Hi,

- Could you please execute `checkMesh -allGeometry -allTopology` and inspect the output (or share it here)?
- I think more info is needed to carry out further inspections. Could you please properly elaborate the simulation settings?

May 26, 2020, 16:07	Increasing Courant Number OpenFoam	#1
Battousai07 New Member Can Unsal Join Date: Sep 2019 Posts: 14 Rep Power: 6	Hi. I am working on a nonuniform, curved vessel. I need to solve the case in laminar transient which i've used pimpleFoam and icoFoam so far. The Courant number continiues to increase. I have tried adjustable time step and defined maxCo as 5 so far. This satisfies the condition but time step continiues to decrease very low values to make the condition satisfied. My mesh is OK in terms of skewness and orthogonatily. What can cause this problem?

May 28, 2020, 17:28		#5
HPE Senior Member Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12	Hi, - Could you please execute `checkMesh -allGeometry -allTopology` and inspect the output (or share it here)? - I think more info is needed to carry out further inspections. Could you please properly elaborate the simulation settings? __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

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May 27, 2020, 04:34		#2
geth03 Senior Member Join Date: Dec 2019 Location: Cologne, Germany Posts: 355 Rep Power: 8	does the solver crash or does it run really slow with high CFL number?

May 27, 2020, 06:33		#3
Battousai07 New Member Can Unsal Join Date: Sep 2019 Posts: 14 Rep Power: 6	Runs with high CFL number. First it was crashing but i have managed to prevent that by introducing nonOrthogonal correctors and nCorrectors

May 28, 2020, 03:03		#4
geth03 Senior Member Join Date: Dec 2019 Location: Cologne, Germany Posts: 355 Rep Power: 8	can you output the courant number for your domain and analyze it with paraview? there is a function for that, which you need to write in controlDict. you can then see where your CFL number is relatively high. also execute checkMesh and check if a new directory is created in polyMesh-directory. if your mesh is broken somewhere the directory will be created. you can then create vtk-files and open it with paraview, so your problematic areas will be highlighted.