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BC for MRF simpleFoam

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Old   July 28, 2014, 17:36
Default BC for MRF simpleFoam
  #1
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M. C.
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Hi all,

I have the following case to simulate with OF 2.3.0.

https://www.dropbox.com/s/19eranpb56...WHOLE_CASE.png

It's about a radial fan inside a complex geometry, where you can see on following picture that: red are patches for inlet, while blue are patches for outlet, other are wall. plus there's a rotating frame (cellZone) for the fan.

Considering no turbulent model at all I set up following BC:

U:

Code:
boundaryField
{

    inlet


    {
       type     pressureInletVelocity;
       phi      phi;
       value    uniform (0 0 0);
    }
   
    outlet
    {
        type            inletOutlet;
    phi          phi;
        inletValue      uniform  (0 0 0);
        value           uniform  (0 0 0);
    }


    wallComp
    {
        type            fixedValue;
        value        uniform (0 0 0);

    }

    boccaglio
    {
        type            fixedValue;
        value        uniform (0 0 0);
        
    }
    blade
    {
        type            fixedValue;
        value        uniform (0 0 0);
    }

    wallAsp
    {
        type            fixedValue;
        value        uniform (0 0 0);
    }

    wallMan
    {
        type            fixedValue;
        value        uniform (0 0 0);
    }

    tubi
    {
        type            fixedValue;
        value        uniform (0 0 0);
    }

    wallExt
    {
        type            fixedValue;
        value        uniform (0 0 0);
    }
       
        
}
and p:

Code:
boundaryField
{
  inlet
 

   {
        type            totalPressure;
        p0              uniform 0;
        phi             phi;
        U               U;
        rho             none;
        psi             none;
        gamma           1.4;
    }
    outlet


    {
        type            fixedValue;
    
    value           $internalField;
    }

   wallComp
    {
        type            zeroGradient;

    }

    boccaglio
    {
        type            zeroGradient;
        
    }
    blade
    {
        type            zeroGradient;
    }

    wallAsp
    {
        type            zeroGradient;
    }

    wallMan
    {
        type            zeroGradient;
    }

    tubi
    {
        type            zeroGradient;
    }

    wallExt
    {
        type            zeroGradient;
    }
        
}
I set up 100 rad/s as rotational speed for the fan.

Just below the fan there's the suction chamber for the fan.
I would expected a (-p) value on this volume, but the pressure plotted is equal to 0; while on discharge line I would expected a (+p) value.

https://www.dropbox.com/s/8ea57zltlyrd8kk/SLICE_P.png

Experimentally if I perform a measure with a differential pressure gauge between suction and discharge, I'm able to measure the overall static pressure for the fan: so the total Dp.

Are results consistent with the BC I set up at inlet & outlet, so pressure shall reach zero value according to the mathematical model? or should I change my BC because effectively, as there's no physical meaning for this solution?

Last edited by student666; July 29, 2014 at 02:24.
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Old   July 29, 2014, 10:12
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is there anybody who can help me, please?

To ask in other way, I would like to understand, after setting rotational speed for the fan, how much is the pressure loss on air channel due to several bends, ecc...

My doubt is to understand if the BC I applied are consinstent with the solution, and which are the excpected BC to obtain what the total static pressure for the fan inside this particular channel.

Thanks a lot.
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Old   July 30, 2014, 13:20
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anybody can help me with this?
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