freestreamPressure & freestream BCs
 

Hi,

i'm still wondering, what freestreamPressure and freestream Boundary Conditions do. I studied the sourcecode, but I think I'm missing something...

What is the difference between

U freestream (derived from inletOutletFvPatchField<Type>)
p freestreamPressure (derived from zeroGradientFvPatchScalarField)

and

U inletOutlet
p zeroGradient

?

Luise

Hi,

i finally ran a simple case to compare the two settings.

The case is a 2d-flow over a cirular cylinder with a Reynolds-number of 5, thus stationary. I used the icoFoam solver for that. The outer boundary patch is also circular and goes coherently around the whole domain, so the boundary conditions are not seperatly defined for inflow and outflow.

The attached graph is a plot of Ux on the outer boundary patch. A difference is clearly visible.

I guess, after reading the sourcecode, that the two settings entail a different schedule for the evaluation of the inletOutlet member functions.

Can anybody confirm that? Other explanations are welcome! Maybe somebody has a deeper knowledge of the code and can give a more elaborate reasoning...

Luise

About freestream/freestreamPressure
 

Hello Luise,

Sorry I can't bring any elaborated explanation on the difference, but I am very interested in this topics. Did you find any further information?

I am running a case with a shaped tube ending with a radiating hemisphere.

I have an inlet with U defined, p zeroGradient, and the outlet I hesitate with U inletOutlet and p zeroGradient, or U freestream, p freestreamPressure... It's supposed to be an open atmosphere outlet.

If you have any advice, it would be more than welcome :)

Regards,

Bertrand

Hi Bertrand,
I am also confused with these boundary conditions, do you have now a clear understanding of the difference between zerogradient pressure and freestreamPressure?
regards
YOng