[Hyllon]

Hello, I'm new to OF. I'm running an axi-symmetric case. It's just a pipe.

Geometry: https://imgur.com/a/YsK1o

The problem is: The velocity varies according to an equation.

This is the equation: https://imgur.com/a/8jDCc

The ONLY variable is ' r ', which is the distance between the center of the tube and any cell in y direction.

I need a boundary condition for that. Any help is appreciated.

Sorry for bad english.

[RobertHB]

You might take a look at the codedFixedValue boundary conditon or the vectorCodedSource entry for the fvOptions dictionary. But i haven't work with any of those and can't tell you if it will work or not.

[einstein_zee]

Originally Posted by Hyllon

Hello, I'm new to OF. I'm running an axi-symmetric case. It's just a pipe.

Geometry: https://imgur.com/a/YsK1o

The problem is: The velocity varies according to an equation.

This is the equation: https://imgur.com/a/8jDCc

The ONLY variable is ' r ', which is the distance between the center of the tube and any cell in y direction.

I need a boundary condition for that. Any help is appreciated.

Sorry for bad english.

Hey,

A subtle way is discussed here. "https://www.youtube.com/watch?v=K-nAF3qAPTc"

[Taataa]

Here is the code that you can put in U file:

inlet
    {
        type            codedFixedValue;
        value           uniform (0 0 0);
        redirectType    parabolaProfile;
        
        code
        #{
            const fvPatch& boundaryPatch = patch();
            const vectorField& Cf = boundaryPatch.Cf();
            
            vectorField& field = *this; 
            scalar Ut = 1;
            scalar C  = 1;
            scalar R0 = 1;
            scalar nu = 1;
            scalar n  = 1;
            
            scalar vel;

            forAll(Cf, faceI)
            {
                scalar dis = Cf[faceI].y() < R0 ? Cf[faceI].y() : Cf[faceI].y() - R0;
                vel = Ut*C*pow(dis*Ut/nu, n);
                field[faceI] = vector(vel, 0, 0);
            }
        #};
    }

Change the variables based on your dimensions. Keep it mind that I assumed that your equation is written considering the origin is at the center of the pipe but you mesh origin is at the bottom of the pipe. If the mesh origin matches the origin of the equation you use the original form of the equation which changes is straight forward.

[Hyllon]

Thanks so much for your help, guys. Im gonna take a look.

[Rvadrabade]

This is very interesting implementation.
If you are familiar with swak4foam/groovyBC ( if not i recommend you/Everyone must learn) .

I am assuming that flow direction is x and radial is y.

Just look at implementation, images are attached.

One can correct mistakes if any.
All the best.

(If swak4foam not compiled, then ask)