[granzer]

Hello,
I am a beginner at using OpenFoam and this may be a basic question. I am using totalPressure BC for my inlet, but I don't understand where should I set the value of total pressure.


<patchName>
{
type totalPressure;
rho none;
p0 uniform 0;
value uniform 0;
}

should it be set in the 'p0' parameter or the 'value' parameter? What is the difference between 'p0' and 'value'. Also, since I couldn't find anything on this it would be great help if you could point me to any literature on this.

[granzer]

Any info on the differences between these two?

[Yann]

Hello Granzer,

You have to define your total pressure with the p0 parameter. "value" is a placeholder which will be read when the solver starts but will be overwritten by the value computed by the boundary condition.

This is due to the fact that most of the boundary conditions in OpenFOAM are derived from few basic ones and "value" is an inherited parameter from these basic conditions.

You can probably find more about this on the forum. For instance here.

About the totalPressure boundary condition, you can find some documentation, depending on the version you are using:

• ESI-OpenCFD (OpenFOAM-v2006):
  • User guide
    
  • Boundary condition header
• OpenFOAM foundation (OpenFOAM-8):
  • User guide
  • Boundary condition header

Cheers,
Yann

[granzer]

PressureinletOutletVelocity&Total pressure

[granzer]

Originally Posted by Yann

Hello Granzer,

You have to define your total pressure with the p0 parameter. "value" is a placeholder which will be read when the solver starts but will be overwritten by the value computed by the boundary condition.

This is due to the fact that most of the boundary conditions in OpenFOAM are derived from few basic ones and "value" is an inherited parameter from these basic conditions.

You can probably find more about this on the forum. For instance here.

About the totalPressure boundary condition, you can find some documentation, depending on the version you are using:

• ESI-OpenCFD (OpenFOAM-v2006):
  • User guide
    
  • Boundary condition header
• OpenFOAM foundation (OpenFOAM-8):
  • User guide
  • Boundary condition header

Cheers,
Yann

Thank you Yann! That is exactly what I was looking for.

[Newtonian]

Originally Posted by Yann

Hello Granzer,

You have to define your total pressure with the p0 parameter. "value" is a placeholder which will be read when the solver starts but will be overwritten by the value computed by the boundary condition.

This is due to the fact that most of the boundary conditions in OpenFOAM are derived from few basic ones and "value" is an inherited parameter from these basic conditions.

You can probably find more about this on the forum. For instance here.

About the totalPressure boundary condition, you can find some documentation, depending on the version you are using:

• ESI-OpenCFD (OpenFOAM-v2006):
  • User guide
    
  • Boundary condition header
• OpenFOAM foundation (OpenFOAM-8):
  • User guide
  • Boundary condition header

Cheers,
Yann

So in that sense is it even relevant what value you input for "value"? In may examples I've seen the value for "value" is set equal to the same value specified for "p0". Is matching the two values a requirement? Or is it just a convention that is used but doesn't really matter because "value" will be overwritten?

[Yann]

No this is not a requirement, it should not be relevant. As you said it is more of a convention to use the same value as p0 and it does not really matter.

[buesinaw]

Where in the OpenFOAM documentation is this explained? In general, there seems to be a lot of confusion as how to set up boundary conditions. Good documentation on the topic of how to set up boundary conditions would help a lot of people. Maybe the documentation exits, but I haven't been able to find it, and it seems that threads like this are a substitute for proper documentation.
I hope I'm wrong. However, if good boundary condition documentation does not exist, how do we as an opensource community advocate for making it happen? Thank you.