[mhiel]

Hi everyone,

I'm trying to simulate turbulent water flow through a pipe (the pipe is half-filled with water, the upper half is air) using interFoam and cyclic boundary conditions with the goal to examine the velocity profile when the flow is fully developed.

The g file is set to:

value ( 0.01 -9.81 0)

to simulate a slight inclination of the pipe (about 1 per mille) which induces a constant potential on the water.
In ParaView I expected to see an acceleration of the water (increasing U) until the flow reaches developed state.
However the results are quite irritating as the U values in the water region are constantly fluctuating on low magnitudes (as can be seen in the attached image) and never reach fixed values. Moreover the velocities are far too slow for the water phase and there is no acceleration of the water phase as anticipated.

I assume I did something wrong with the cyclic boundary conditions or other settings but I'm new to OF and would appreciate any help/ideas.

Here's a bit more information:

my U file:

internalField   uniform ( 0 0 0 );

boundaryField
{
    inlet
    {
        type            cyclic;
    }
    walls
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    outlet
    {
        type            cyclic;
    }
}

p_rgh:

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            cyclic;
    }
    outlet
    {
        type            cyclic;
    }
    walls
    {
        type            fixedFluxPressure;
        value           uniform 0;
    }
}

g:

value           ( 0.01 -9.81 0 );

I attached the whole case if you'd like to run it yourself.
Note that in the case the orientation of the pipe axes differs from what I've described above (which i did to avoid confusion). Thus in the case g reads: ( 0 0.01 -9.81 )

mhiel