# MRF-Boundary Condition U and equivalent for SRF Urel

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 March 4, 2024, 15:09 MRF-Boundary Condition U and equivalent for SRF Urel #1 New Member   Daniel Join Date: Feb 2024 Location: Austria Posts: 5 Rep Power: 2 Hei, i have a hard time bc I have to do a MRF and a SRF Simulation of a pump turbine- in my MRF my U look like this: Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { IF_LAUF_LEIT { type cylindricalInletVelocity; axis (0 0 1); origin (0 0 0); axialVelocity constant 0; radialVelocity constant -10; rpm constant 800;; value uniform (0 0 0); } IF_LAUF_SAUGROHR { type zeroGradient; } "(cP_cyclicA|cP_cyclicB)" { type cyclic; } "(NABE|KRANZ|SCHAUFEL)" { type fixedValue; value uniform (0 0 0); //Wenn hier alle 3 Null stehen dann dreht es sich mit omega } } // ************************************************************************* //``` the simulation looks goof to me. But I don't understand what the radial component exactly is. is the 10 m/s a velocity in Cartesian or cylindrical components? I think in cylindrical bc you have to define axial and radialvelocity. How can I understand the 10 m/s in radial direction? is this an absolut velocity or a relativ? how can I find the equivalent for Urel for the SRF simulation. I found this in on of the tutorials Code: ```dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { IF_LAUF_LEIT { type SRFVelocity; inletValue uniform (-10 0 0); relative no; value uniform (0 0 0); }``` everything else stays the same as in the MRF. what exactly is the inlet value? and do I need to put relativ yes or no? To compare both simulation I need equal BC... But I don't understand if the SRFVelocity Vektor is in cartesian coordinates or also in cylindrical like the BC at the MRF ? Can someone help me please...

 Tags multi reference frame, openf, single reference frame