- **OpenFOAM Running, Solving & CFD**
(*http://www.cfd-online.com/Forums/openfoam-solving/*)

- - **Physical model: MRF RANS**
(*http://www.cfd-online.com/Forums/openfoam-solving/129249-physical-model-mrf-rans.html*)

Physical model: MRF RANSDear Foamers,
again I have a question. I am simulating a wind turbine, using SIMPLE, the MRF approach with a 120° wedge and cyclic boundaries and RANS (kOmegaSST) turbulence modelling. Currently I am trying to figure out the exact physical equations I am actually using. I do know and understand: - the Navier Stokes equation and its RANS formulation - the formulation of the Navier Stokes equation in its MRF formuation (from here: http://openfoamwiki.net/index.php/Se...RF_development) What I don't understand: - How do both formulations look like in combination? - Does MRFSource in fvOptions only add the Coriolis term? - Would the MRF approach work for unsteady flows? As I understand, for unsteady flow there have to be considered further time-dependent terms. If somebody knows a helpful reference or already has figured it out, I would be greatful for any help. I am not very experienced in reading the source code, but I am also thankful for hints, where in the code to look. Best regards Julian |

Hi,
my current thoughts: The formula looks like the one described in the link above, but instead of kinematic viscosity (nu) I simply have (nu + nut). Does that sound right? Best regards Julian |

as far as I know you can use pimpleFoam (an unsteady solver) with fvOption where you'll be able to add MRF zones. I believe you can use any turbulence model available with pimple.
best |

Dear farhad,
thanks for your reply. Good to know, that fvOptions does work with pimple, too. Any other suggestions, how the Navier Stokes equation looks in the combined MRF + RANS formulation? Best regards Julian |

Quote:
the file MRFZone.C contains a method called correctBoundaryVelocity(). There the velocity at all boundaries within the MRFZone are corrected, i.e. the solid body rotation is applied. Code:
`void Foam::MRFZone::correctBoundaryVelocity(volVectorField& U) const` |

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