[baS]

Dear foamers,

to keep it simple at first i want to simulate the incompressible flow of air with a suction. Later on i have to simulate the compressible flow of air with a second (hot) gas with suction.

I have a box with the dimension of 0.9m / 0.75m / 3.5m.
On top of the box i have an circular outlet with the diameter of 0.1 m.
On the bottom i have the inlet with the same size.

I have an exhaustion on top. For simplification i want to set a constant velocity at the outlet.

I solve with pisoFoam.
After a short simulation time i receive very high velocities (> 60 m/s, average velocity at the outlet = 3.9 m/s) at the edge of the inlet.
For the interior cells of the inlet i get a backflow out of the domain.

I am not sure if my boundaries are ok. I didn´t find some working examples for suction.

My boundaries are:

epsilon:
boundaryField
{
INLET
{
type fixedValue;
value uniform 14.855;
}
OUTLET
{
type zeroGradient;
}
WALL
{
type epsilonWallFunction;
value uniform 14.855;
}
}

k:
boundaryField
{
INLET
{
type fixedValue;
value uniform 0.375;
}
OUTLET
{
type zeroGradient;
}
WALL
{
type kqRWallFunction;
value uniform 0.375;
}
}

nut
boundaryField
{
INLET
{
type calculated;
value uniform 0;
}
OUTLET
{
type calculated;
value uniform 0;
}
WALL
{
type nutUWallFunction;
value uniform 0;
}
}

p:
boundaryField
{
OUTLET
{
type zeroGradient;
}
INLET
{
type fixedValue;
value uniform 0;
}
WALL
{
type zeroGradient;
}

}

U:
boundaryField
{
OUTLET
{
type fixedValue;
value uniform (0 0 3.9);
}

INLET
{
type zeroGradient;
}
WALL
{
type fixedValue;
value uniform (0 0 0);
}

}

Does anyone have a suggestion how to set the boundaries?
Thank you for your reply and sorry for poor english

Sebastian