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Old   March 13, 2018, 21:01
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  #21
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Pablo Higuera
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Hi Chen,

olaFlow is written and tested to work in parallel, if you experience any differences in the unmodified version, please report it, as it would most probably be a bug. However, I have never experience such.

Probably there are some glitches in your new implementation that might need to be programmed to be parallel-aware.

Best,

Pablo
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Old   April 16, 2018, 08:15
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Dear all,

I have just released a library that provides modified versions of k-ε and k-ω SST turbulence models to simulate correctly multiphase systems and mitigate turbulence build-up effect.

You can find all the information in the release post: https://sites.google.com/view/olaflo...ve-simulations

I hope that you find it useful.

Best,

Pablo
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Old   April 16, 2018, 12:28
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Hua Zen
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Quote:
Originally Posted by Phicau View Post
Dear all,

I have just released a library that provides modified versions of k-ε and k-ω SST turbulence models to simulate correctly multiphase systems and mitigate turbulence build-up effect.

You can find all the information in the release post: https://sites.google.com/view/olaflo...ve-simulations

I hope that you find it useful.

Best,

Pablo
Thanks Phicau for your releasing this contribution. Can you give some explanation how your new implementation of turbulence model mitigate turbulence build-up effect?
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Old   April 16, 2018, 20:32
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Pablo Higuera
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Hi Hua Zen,

Check this reference out:

Application of a buoyancy-modified k-ω SST turbulence model to simulate wave run-up around a monopile subjected to regular waves using OpenFOAM
Brecht Devolder, Pieter Rauwoens & Peter Troch
Coastal Engineering (2017), vol. 125, pp. 81–94
https://doi.org/10.1016/j.coastaleng.2017.04.004

Best,

Pablo
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Old   April 17, 2018, 11:17
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Hi Phicau, I've read the paper by Devolder et al. (2017), in which an additional buoyancy term is used to suppress the spurious turbulence generation at the interface. From your blog, two additional turbulence models are implemented(kEpsilonMultiphase, kOmegaSSTMultiphase), what is the difference between these two implementation and that of Devolder et al. (2017)?
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Old   April 17, 2018, 22:37
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Hi Hua Zen,

the problem in OpenFOAM is that incompressible turbulence models are not prepared for multiphase flows. They assume a constant rho, since under the incompressibility assumption, it will go out of the differential operators. In incompressible multiphase flows, the density of each phase is constant, but the density of the system changes throughout the domain depending on the VOF function value in each cell.

kEpsilonMultiphase and kOmegaSSTMultiphase implementations are exactly the same as provided by OpenFOAM, but the density (rho) has been modified so that the one provided by the multiphase solver (e.g. olaFlow) is used.

Best,

Pablo
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