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RuiVO December 7, 2011 07:41

OpenFoam/FLUENT difference in cilinder case
4 Attachment(s)
Good day to you all,

I am running the same case file in OpenFoam and in Fluent, with the most similar Boundary Conditions possible. The problem is that pressure field is similar but velocities are totally different, almost 3 times less in OpenFoam. I do not know what the problem is, I have not attached the Fluent Case file since it is too large. I have however attached files of the OpenFoam case. God I love the maximum size of 97 kb for file attach :D

Just a heads up of what I have done:
OpenFoam case is run using rhoSimpleFoam solver in laminar regime with total pressure inlet of 4907 and fixed pressure outlet of 3877. The converged inlet velocity is about 38 to 40 m/s.

Fluent case is runned on a pressure based solver, laminar regime with same boundary conditions and the converged velocity inlet is about 140 m/s.

To my knowledge, both solutions have converged.
Attachment 10355

Attachment 10356

Attachment 10360

Attachment 10361

Best Regards

Rui Oliveira :D

jackpap December 11, 2011 20:44

Are you sure your viscosities and densities are set in the same way?
Also in Fluent are you sure you are comparing the right pressures and that you don't have an offset / "Operating pressure" ?

RuiVO December 12, 2011 15:26

Hi jackpap ! Yes . Anyway I have solved the problem ! :D Now I use rhoPisoFoam with total pressure boundary condition at the inlet as before, but !!! now I assing the following change (boundary conditions are not exact, cant remember the name of exact term since I dont have the file at hand now but you get the picture):

type totalPressure
p0 4907
value 3877
rho rho /*THIS IS WHAT IS MISSING !!!!*/

After I changed the boundary conditions at inlet ... problem solved :D

Best regards

Rui Oliveira :D

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