# I want to set normal velocity 0 at boundary

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 November 21, 2019, 15:15 I want to set normal velocity 0 at boundary #1 New Member   Join Date: Sep 2019 Posts: 18 Rep Power: 6 Hi, I have a cylinder (axisymetric in z direction) as computational domain. Inlet and outlet are periodic. I want to to set normal velocity 0 at the sides. The slip condition just do not allow velocity to go outwards. But it can point inwards with non 0 normal component. I do not want this. The noSlip condition could works but I do not need to give a 0 value to the tangent components. I tried with directionMixed writing the following: Code: ``` sides { type directionMixed; refValue uniform (0 0 0); refGradient uniform (0 0 0); valueFraction uniform (0 0 0 0 0 1); }``` But I just get 0 in z component, which is the opposite that I want. I want 0 in radial direction and whatever in azimutal and z direction. Could anyone help me?

 November 27, 2019, 16:19 #2 Senior Member     Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12 How would 'slip' condition allow non-zero inward velocity? __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

 November 27, 2019, 18:16 #3 New Member   Join Date: Sep 2019 Posts: 18 Rep Power: 6 Hi HPE, thanks for answering. Perhaps it is intentionated, I mean, that the own OF only prevents the normal vector out with the slip condition. I attached a picture that demonstrates it. There you will see the value of the velocity field vectors on the cylinder walls. They should be tangential but it seems that the slip condition simply removes the normal components pointing outwards. Does anyone know if directionMixed can eliminate both the normal component pointing outwards and inwards? slipConditionCylinder.0001.png

 November 27, 2019, 23:12 #4 Senior Member     Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12 Hi, There is no way that 'slip' condition can introduce flow into the domain unless a setup or postprocessing issue. Is there any chance for you to share your case minimally? __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

 November 28, 2019, 18:07 #5 New Member   Join Date: Sep 2019 Posts: 18 Rep Power: 6 Hi, Here you have the case with the solver and the function for initial profile for B. Thanks!, David. cylinderSmallBzSlip_ (3).zip

 Tags directionmixed bc, normal velocity, noslip, slip b.c.