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steady-state MRF with Rushton Turbine mixing vessel verification

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Old   July 25, 2022, 04:15
Default steady-state MRF with Rushton Turbine mixing vessel verification
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hi all,

since 2 monthes i am trying to reproduce a paper https://www.sciencedirect.com/scienc...92687506001075 to verify the MRF-model for a mixing vessel with a 6 blade rushton turbine impeller (see pic 1 for geometry).

my main focus in the beginning was first to achieve a good result regarding the Power Number and then check the velocity and turbulence field. However, the results i achieved with various turbulence models were 20% lower than the literature number and the deviation with the Ansys Fluent solver results were also around 15%.

Additionally, i could not achieve any convergence for the majority of meshes/cases i created. the only time i achieved convergence was with the k-Epsilon model.

Nowhere i found a case that tries to validate the MRF for simpleFoam in a closed domain!

Here is a list of things about what i tried:

- solver: simpleFoam -> SIMPLE and SIMPLEC algorithms
- space discretization: for the start of the simulation first order for convection, then switch to 2nd order upwind for U and for tubulence 2nd order upwind/TVD/NVD. laplacian according to my mesh quality.
- turbulence models: k-Epsilon/realizable k -Epsilon/LaunderSharmaKE/kOmegaSST
- mesh: cell shape: complete hexahedral/complete polyhedral/polyhedral prism layer and hexahedral core / with and without prism/inflation layers (3/5/10) -> so that wall resolved or y+ in log-Layer
- boundary conditions: fluid initially at rest, top of tank is free surface (slip/symmetry). turbulence parameters: wall function or fixed Value (10e-12) for wall resolved models.

convergence check: residual plots, sample Points for p and U at 9 locations, Torque and forces at impeller+shaft and also walls.

does anybody know if there exists a publication regarding verification of MRF-approach for a mixing vessel for single-phase flow?
i know that there are two-phase mixing vessels, but that makes it hard to verify the single-phase approach.

any hint/help is appreciated!
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Last edited by geth03; July 28, 2022 at 03:38.
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Old   July 29, 2022, 10:41
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My colleague Darrin conducted this study a bunch of years ago and published the results in a webinar with Pointwise. You can access the material here:

https://info.pointwise.com/webinar-c...er-requirement

You have to provide you name and email to get access to the page. The slides have all the case setup details and results. The case is included as well. If you don't want to jump through the registration hoops, send me a DM and I'll send you the slides through email.

-Chris
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Old   July 29, 2022, 11:36
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hi Chris,
thanks for reaching out.

i already saw this video on youtube. did download the files now, unfortunately i don't have access to pointwise, is there a way to extract the mesh data from .pw-file directly to openfoam format without access to pointwise software?

regards
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Old   July 29, 2022, 11:45
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I can pack it up for you. Send me a DM.
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