OpenFoam vs Fluent
I have run several test case with OF and Fluent with similar settings.
I have found that fluent is more stable , accrue and faster than OF
also OF is very sensitive to mesh quality but Fluent not.
I hope it is be useful for anyone who like to compare OF with fluent
I'd like to know in a bit more detail your comparison.
What kind of test cases do you have?
the equivalent of pimpleFoam, in fluent is PISO. therefore ,
I have compared pimpleFoam in OF vs PISO in fluent
my test cases are, flow around airfoil with flap , cylinder + square, ....
setting for both software:
grad========> leastSquares (in OF, I should cellLimited for convergency)
spatial Discretization ===========> linearUpwind and limitedLiniear for OF and second order Upwind for fluent
turbulence =============> kw-SST
convergence criteria in each time step =============> 1e-5
in the case of airfoil I have 430,000 element and this mesh is very orthogonal but for reducing cell numbers I have large aspect ratio up to 200
also the OF results is not smooth as Fluent
Could you please post your fvSchemes and fvSolution files for your OpenFOAM setup.
I have found that the main deficiency of openfoam is that it is very sensitive to mesh quality.
if I divide the mesh quality to very good, good , medium,bad ,very bad then
the OF and Fluent have the same performance on the very good meshes.
OF performance on the good meshes is lower than FLUENT and it can not handle other meshes.
FLUENT can handle medium and bad meshes very well.
OpenFOAM is an open-source CFD tool -- you could optimize for your needs.
I found lot of advantages in OpenFOAM while post processing my simulation data.
in particular --> Tensorial operations.
I agree with you that OF is a good Open Source code
I hope in the future OF remove its dependency to meshes and it become a very powerful
the current deficiency is a big problem. in the complex geometries we can not create a
very good mesh
I may disagree with you mechy, but your post is not "useful for anyone who like to compare OF with fluent", since a lot of things are missing.
If you want to add usefull info, add your full OF case and Fluent case.
Because you don"t give your BC setting for OF, neither Fluent setting, initialization method, etc ...
did you follow Discretisation Best Practice for Industrial CFD with OpenFOAM or s.th like that?
in post reply number 3 and 5 you can find setting for OF and FLUENT
for OF my fvScheme and fvSolution are added to post reply5 ;
the BC are as follow
| OF | FLUENT
inlet | fixedValue | velocityInlet
outlet | inletOutlet |
| or zeroGradient | pressureOutlet
please see my fvScheme , it is equal to recommended setting by JASAK
also I check Gauss for Grad but nothing changed.
This is better, not perfect:
- Did you use hybrid initialisation in Fluent ?
- initial value in OF ?
- about CFL: (i didn't see your controlDict by the way .... upload the full case again) if Fluent use 10x bigger time step, this is probably not Euler fort the temporal discretisation ...
- what maxCo do you use ?
- residus are not the same in OF / Fluent: did you use another convergence criterious, like Cp/ Cl convergence , which is more valid ?
- in your fvsolution, p tolerance should be smaller
- you say you follow the LASAK rules, but use nNonOrthogonalCorrectors=4: you should use 0 in your case.
- you use "zeroGradient" for pressus outlet, while Fluent use "pressurOutlet" : this is _not_ the same BC at all. In your case, the chord length seem to be really too small for a zeroGradient BC (if you look in this forum, you willl see good result with 20 to 40, and use other BC like freestreamPressure and cie.)
This is some critics (in the constructive way) i can make, and i am not an expert here. I use OF and Fluent almost every day, and i disagree with your first post. Sometime, Fluent are faster, sometime this is OF. same for accuracy.
So in short, try to improve your settings ... this take time (a real difference with Fluent), and we can share info about this ...
in both software the initial velocity and pressure is zero and initial k and omega is inlet conditions.
in both software I use constant deltaT=5e-5
for airfoil I use a very good mesh and a good mesh in both mesh fluent give the same result but on good mesh the OF convergence is very slow.
fvSolution with current p tolerance is sufficient on very good mesh and it give the fluent results
also if I use nNonOrthogonalCorrectors=0 the solution convergence become slower
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