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I want to set normal velocity 0 at boundary

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Old   November 21, 2019, 15:15
Default I want to set normal velocity 0 at boundary
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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?
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Old   November 27, 2019, 16:19
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How would 'slip' condition allow non-zero inward velocity?
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Old   November 27, 2019, 18:16
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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
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Old   November 27, 2019, 23:12
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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?
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Old   November 28, 2019, 18:07
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Hi,

Here you have the case with the solver and the function for initial profile for B.

Thanks!,
David.

cylinderSmallBzSlip_ (3).zip
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directionmixed bc, normal velocity, noslip, slip b.c.

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