[Frenk_T]

Hello Everybody,

I'm working with the solver interFoam (OpenFOAM-2.4.0), trying to reproduce the results shown in "Comparison of experimental and Computational Fluid Dynamics (CFD) studies of slug flow in a vertical riser" by M. Abdulkadir, V. Hernandez-Perez, S. Lo, I.S. Lowndes, B.J. Azzopardi.

I have test several parameters (mesh size, time step, maxCo, cAlpha, fvSchemes) but so far I'm not able to reproduce the results in terms of the rise velocity of Taylor bubble.

Maintaining a sharp and accurate interface is far from trivial. As you can see in the attached figures it seems that I can not avoid the effects of numerical smearing of the interface. The solution depends also on the initial condition (internal field) of k and epsilon (Fig. "instability" is obtained changing only the internal field for k,epsilon ---> Rayleigh-Taylor instability?).

Is there any problem with my settings?

Attached are an image of the mesh, snapshots and a tar.gz file with the 0, System folders and checkMesh output.

Any help is appreciated.

Thanks,

Francesco

[akidess]

I think your mesh is far too coarse. In interFoam (VOF) you should strive to resolve every bubble, otherwise you need to use an Euler-Euler approach. Also, limit your timestep to very small Courant number (see http://dx.doi.org/10.1088/1749-4699/5/1/014016). Using standard k-epsilon for a multiphase simulation might not be ideal either, perhaps you can use LES.

[Frenk_T]

Dear Anton, thank you for your reply.
You are right about the mesh: however in the article that I attached, a similar mesh is employed with good results (they use Star-CCM+). So I was trying to replicate exactly the same case with OpenFoam. For the same reason I am using standard k-epsilon. Anyway I will try your advices.

[Frenk_T]

Just to give an update:
I changed solver and with multiphaseEulerFoam I have interesting results. I attach a screenshot; I can see the formation of a Taylor bubble even with a really coarse mesh. The aspect ratio plays an important role (the two meshes have the same number of cells in the z direction).