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Setting atmopheric boundary layer for inlet

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Old   June 16, 2016, 10:27
Default Setting atmopheric boundary layer for inlet
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Almond Wong
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Hi,

How can I set up an atmospheric inlet velocity profile?
I am very new to both CFD and OpenFOAM, so a step by step explanation would really be appreciated.

Do I just add this in the 0/U file:
Quote:
inlet
{
type atmBoundaryLayerInletVelocity;
Uref 10.0;
Zref 500;
zDir (0 0 1);
flowDir (1 0 0);
z0 uniform 0.1;
zGround uniform 0.0;
value $internalField;
}
And the surround walls and top wall set to either slip or symmetry?
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Old   June 23, 2016, 05:39
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You can check the turbine siting tutorial. There the atmospheric boundary layer is used. The values that you need to define should be pretty self explanatory. In an earlier version I had two issues with the atmBoundaryLayerInletVelocity:
1. There was a minimum roughness length and any z0 below this value was set to this min value.
2. The reference velocity was set to be equal the gradient velocity. (velocity profile became constant after the height zref)

IDK if this has changed in the recent versions but maybe keep it in mind if the results look weird.
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Old   June 24, 2016, 07:16
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hi bazinga, thanks for the reply!!! Can I ask a few question regarding this?

I set up my profile as in the tutorial and BC as slip/symmetry. However, in the horizontal axis (z axis) there seem to be a built up of a velocity profile as well where it reduces to 0 at the wall. Do you know why??

my ABLCondition file:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  dev                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/

Uref                 10.0;
Zref                 500;
zDir                 (0 0 1);
flowDir              (1 0 0);
z0                   uniform 0.1;
zGround              uniform 0.0;
value                $internalField;

// ************************************************************************* //
0/U file:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  dev                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#include        "include/initialConditions"

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform $flowVelocity;

boundaryField
{
    outlet
    {
        type            inletOutlet;
        inletValue      uniform (0 0 0);
        value           $internalField;
    }

    inlet
    {
        type            atmBoundaryLayerInletVelocity;
        #include        "include/ABLConditions"
    }

    obstacles   
    {
        type            uniformFixedValue;
        uniformValue    (0 0 0);
        value           uniform (0 0 0);
    } 

    ground
    {
        type            uniformFixedValue;
        value           uniform (0 0 0);
        uniformValue    constant (0 0 0);
    }

    #include "include/sideAndTopPatches"
}


// ************************************************************************* //
include/sideAndTopPatches file:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  dev                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/

top
{
    type symmetry;
}

sides
{
    type symmetry;
}

"proc.*"
{
    type            processor;
}

// ************************************************************************* //
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Old   June 24, 2016, 07:20
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Almond Wong
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this is the velocity profile that came out
Attached Images
File Type: png Untitled.png (40.9 KB, 59 views)
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Old   June 24, 2016, 11:40
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this is the velocity profile that i got. the profile is good until it drops suddenly to zero as it reaches the top.
Attached Images
File Type: png ssssss.png (6.2 KB, 70 views)
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Old   September 28, 2016, 04:36
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don't know if this problem has been solved. From the pic you attached, it seems like the side faces and the top are treated like wall type.maybe check your boundary file in polymesh.
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Old   October 21, 2016, 00:47
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I agree with ruby_nuaa. Maybe upload your files and I will have a look.
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Old   January 6, 2024, 04:26
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Marķa Rosales
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Quote:
Originally Posted by ruby_nuaa View Post
don't know if this problem has been solved. From the pic you attached, it seems like the side faces and the top are treated like wall type.maybe check your boundary file in polymesh.

Hi ruby_nuaa, maybe you find already your solution (its been some years after!). I prefer to use as top BC the fixed value that comes from solving the formula of inlet BC at that top height. Hope this helps new foamers if they read this thread
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