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Old   August 28, 2009, 04:59
Default Inlet varying with time
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jhegar
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hello everybody!!

I have to simulate a pipe in which the water flow input depends on the time. What Im trying, is to set a velocity in the inlet path that changes with the time (my problem is inkompressible). But I have no idea how I can do this. And by the moment I have not found any usefull information that could help me with this task.

Could any one there help me with this problem??

Thanks for your time and help.
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Old   August 28, 2009, 05:25
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Julien Schaguene
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Hi,
did you make a search on the forum? I think this topic had been discuss before.
From what I read before, there are multiple solutions:
- the one I'm using, modifying inlet velocity at each time step by adding a piece of code in the solver.
- groovyBC should also give a solution
- I also read about timeVaryingInlet but I never tried it.

If you want some advices to "modify" the solver (in fact, just adding an include), you can mp me.

regards,

Julien
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Old   August 31, 2009, 04:59
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Hi,
thank you very much. I will try with groovyBC, anyway Ill ask you for some advices on modifying the solver, because I think that in some moment I will need to do it.
Thank you very much for your help.
Have a nice week.
Jorge
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Old   August 31, 2009, 05:50
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Here's a bc I use for time-varying conditions.

bc_whatever
{
type timeVaryingFlowRateInletVelocity;
fileName "inlet1.dat";
flowRate 0.1944;
outOfBounds repeat;
value uniform ( 0 0 0 );
}

the inlet1.dat file is placed in the case directory and for me it looks like this

(
(0 0)
(13.89e-3 0.1944)
(27.78e-3 0)
(100.0e-3 0)
)

this will produce a triangular inlet wave with 27.83 ms duration, every 100 ms.

copy/paste from the bc-file found at src/finiteVolume/fields/fvPatchFields/derived/timeVaryingFlowRateInletVelocity
Code:
    Example of the boundary condition specification:
    @verbatim
    inlet
    {
        type            timeVaryingFlowRateInletVelocity;
        flowRate        0.2;         // Volumetric/mass flow rate [m3/s or kg/s]
        value           uniform (0 0 0);  // placeholder
        fileName        "$FOAM_CASE/time-series";
        outOfBounds     repeat;           // (error|warn|clamp|repeat)
    }
    @endverbatim

Note
    - The value is positive inwards
    - may not work correctly for transonic inlets!
    - strange behaviour with potentialFoam since the U equation is not solved
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