[al0909]

Hello Foamers!!

I'm a newbie to OpenFOAM and i'm struggling a bit with a case I have to run for my PhD.

The idea is the following:
We are dealing with half a pipe (Diameter: 0.05m - Lenght: 0.4m) and we want to simulate the flow passing inside it and compare it with experimental data.

We are using air (which we consider to be following the perfect gas law), the exit Mach number should be 0.65 (so we go for a compressible solver --> rhoSimpleFoam), and the static pressure at the outlet should be the ambient pressure (98916Pa).
The walls of the pipe are considered adiabatic.

I measure a total pressure at the inlet as well as a total temperature.


Therefore: I am setting up the following files for my case:

0/p
----------------------------------------------
dimensions [1 -1 -2 0 0 0 0];

internalField uniform 98916;

boundaryField
{
inlet
{
type totalPressure;
p0 uniform 131392;
gamma 1.4;
}
lateralwall
{
type zeroGradient;
}
symmetrywall
{
type symmetryPlane;
}
outlet
{
type fixedValue;
value uniform 98916;
}

0/U
----------------------------------------------
dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 -217);

boundaryField
{
inlet
{
type fixedValue;
value uniform (0 0 -217);
}
lateralwall
{
type fixedValue;
value uniform (0 0 0);
}
symmetrywall
{
type symmetryPlane;
}
outlet
{
type zeroGradient;
}
}

0/T
----------------------------------------------
dimensions [0 0 0 1 0 0 0];

internalField uniform 277;

boundaryField
{
inlet
{
type totalTemperature;
T0 uniform 300;
gamma 1.4;
}
lateralwall
{
type zeroGradient;
}
symmetrywall
{
type symmetryPlane;
}
outlet
{
type zeroGradient;
}
}


I'm using a k-omega SST turbulence model, and running with rhosimpleFoam solver.
I don't get any error messages, but I cannot manage to make this computation converge.
My pressure distribution after some iterations increases and makes no sense (values close to 1.3e5 Pa) and neither does the velocity.
Is something wrong with my boundary conditions? Am I over-constraining or under-constrainig the problem?

Any help would be much appreciated.
Thanks in advance