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jorgehegar August 28, 2009 03:59

Inlet varying with time
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.

Schag August 28, 2009 04:25

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.



jorgehegar August 31, 2009 03:59

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.

niklas August 31, 2009 04:50

Here's a bc I use for time-varying conditions.

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

    Example of the boundary condition specification:
        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)

    - 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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