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large_eddy May 29, 2013 14:55

BuouyantBoussineqLES pressure problem
 
2 Attachment(s)
Hello Foamies,

I'm trying to implement a turbulent flow field using the BuouyantBoussinesq solver.
My boundary conditions are at first as follows:

dimensions [0 1 -1 0 0 0 0];
internalField uniform (0 0 0);
boundaryField
{
left
{
type cyclic;
}
right
{
type cyclic;
}
top
{
type zeroGradient;
}
bottom
{
type fixedValue;
value uniform (0 0 0);
}
back
{
type cyclic;
}
front
{
type cyclic;
}
}


I'm using funkysetFields afterwards to write an initial wind- and pressure field.
Now the problem: After the first solver iteration the original pressure scales changes rapidly, even into negative scale. After a couple iterations this leads to singularities of unreal high numbers at the bottom corners of the flow domain. I attached two pictures for illustration purpose. The first shows the initial pressure field, second shows the build-up of the singularities.

Has anybody overcome similar problems with LES, or can give any advise on how to set the boundary conditions for the simulation of turbulent fields?

Thanks in advance,
edit

large_eddy May 31, 2013 05:55

Problem solved
 
The pressure singularities were eleminated by using funkySetFields to set the right pressure levels to the flow domain. Afterwards I decreased the timesteps to 0.25 sec to keep Courant numbers low. After a couple of minutes timesteps were increased up to 1.0 sec. The pressure field was stable throughout the simulation run.


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