water inject tube, huge different results by icoFoam and Fluent
 

Hi all, I am a beginner to use openfoam. A simple case: water injection into 2D tube, x*y=2*0.4. But the velocity distribution is huge different when use openFOAM and Fluent. Why?

The icoFoam and Fluent were both used to simulate the steady-state process. The BCs are:

openFOAM
left: fixed velocity 0.05 m/s, zeroGrident for p
right: zeroGrident for U, fixed 0 for p
upDown: fixed (0,0,0) for U, zeroGrident for p
frontback: empty

fluent
left: velocity-inlet 0.05 m/s, zeroGrident for p
right: pressure-outlet, fixed for pressure
upDown: wall, no-slip

Attached is the comparisons of the openFOAM and Fluent results. Thanks!

Hi cchuran

what did you set for the turbulence in both cases? it seems that in openFoam you have laminar flow while in fluent the profile looks like turbulent.

Thanks for your reply. The fluent also uses laminar model (the same as openFOAM)

kinematic viscosity of 0.01
 

Have a look into the transportProperties inside constant folder.
The kinematic viscosity of 0.01 is ten thousand times larger than the one of water 1.004e-6. This gives you a perfect parabolic profile even withing this large diameter tube.

Cheers

Fabian

It looks like that you are simulating different Reynoldsnumbers and in assumption that you set the velocity (0,05 m/s) and the viscosity (water=1.04e-06) for both Fluent and OF, there is one left, the scaling of your geometry!

Please, verify that your case in fluent AND in OpenFOAM is set up in meters.

If you want to simulate laminar pipe flow, the critical Reynoldsnumber should be

Re_crit=u*d/<2320

P.S.:
your OF simulation looks for laminar pipe flow right, cause the peak velocity of the parabolic profile should be around 2*u_in = 2*0,05=0,1m/s

you fixed your problem?