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-   -   Underexpanded Jets - code crash - Help (http://www.cfd-online.com/Forums/openfoam-solving/73093-underexpanded-jets-code-crash-help.html)

sankarv February 26, 2010 08:06

Underexpanded Jets - code crash - Help
 
Hello OpenFoamers

I need some help with the boundary conditions desperately. As I have mentioned in my previous post, I am trying to simulate an under-expanded jet. I have successfully simulated the same problem using Fluent. Now
I am trying to use OpenFoam to compare the two solvers. (BTW,
This is my first ever OpenFoam simulation.....)
I am using rhoCentralFoam. It is a 2D grid I imported from Fluent using fluentMeshtoFoam.

Here is the configuration.
_________________________________
| free-stream |
| |
| wall_inlet |
| |Outflow
| |
! |
! jet_inlet axis |
!-------------------------------------|


Here is my 'p' file
dimensions [1 -1 -2 0 0 0 0];
internalField uniform 10000.0;
boundaryField
{
Jet_inlet
{
type totalPressure;
value uniform 300000.0;
p0 uniform 300000.0;
U U;
phi phi;
rho none;
psi psi;
gamma 1.4;
}
wall_inlet
{
type zeroGradient;
}
axis
{
type zeroGradient;
}
outflow
{
type pressureTransmissive;
value 10000.0
}
top_boundary
{
type pressureTransmissive;
value 10000.0
}
}
// ************************************************** *********************** //

For the outflow and top_boundary (freestream) I have tried wave transmissive, zeroGradient,pressureTransmissive boundary conditions.
But the simulation always crashes when the initial transient shock reaches the outflow.

Here is my 'U' file
dimensions [0 1 -1 0 0 0 0];
internalField uniform (0 0 0);
boundaryField
{
Jet_inlet
{
type fixedValue;
value uniform (319.2 0 0);
}
wall_inlet
{
type fixedValue;
value uniform (0 0 0);
}
axis
{
type zeroGradient;
}
outflow
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
top_boundary
{
type zeroGradient;
}
}

Here is my 'T' file
{
Jet_inlet
{
type totalTemperature;
value uniform 300;
T0 uniform 300;
U U;
phi phi;
rho none;
psi psi;
gamma 1.4;
}
wall_inlet
{
type zeroGradient;
}
axis
{
type zeroGradient;
}
outflow
{
type zeroGradient;
}
top_boundary
{
type totalTemperature;
value uniform 300;
T0 uniform 300;
U U;
phi phi;
rho none;
psi psi;
gamma 1.4;
}
}

For the outflow and top_boundary (freestream) I have tried wave transmissive, zeroGradient,pressureTransmissive boundary conditions for
pressure.
But the simulation always crashes when the initial transient shock reaches the outflow.

I must admit I am using the boundary conditions by looking at similar files in the rhoCentralFoam. I would sincerely appreciate if someone can
tell me what is wrong with my set-up and also if possible tell me the
meaning of the various keywords in the b.c files 'p','U' and 'T'. I can
make an educated guess about some of them, but I would be more comfortable hearing that from experts out there...


Please help

Thanks
Vaidya


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