[Mateus Elias]

I running a SA turbulent model, and would like to confirm if my boundary conditions of nut and nuTilda are ok.


nut
BoundaryField
{
inlet
{
type freestream;
freestreamValue uniform 0.14;
}

outlet
{
type freestream;
freestreamValue uniform 0.14;
}

lowerWall
{
type slip;
value uniform 0;
}

frontAndBack
{
type slip;
value uniform 0;
}

upperWall
{
type nutLowReWallFunction;
value uniform 0;
}

cpolaina
{
type nutLowReWallFunction;
value uniform 0;
}
}

***********************
nuTilda
boundaryField
{
inlet
{
type freestream;
freestreamValue uniform 0.14;
}

outlet
{
type freestream;
freestreamValue uniform 0.14;
}

lowerWall
{
type slip;
value uniform 0;
}

frontAndBack
{
type slip;
value uniform 0;
}

upperWall
{
type fixedValue;
value uniform 1e-20;
}

cpoliana
{
type fixedValue;
value uniform 1e-20;
}

}

Are these values right?

Kind regards.

[HPE]

Hi,

- You can estimate the initial conditions, and designate the boundary conditions for the SpalartAllmaras model by using the NASA Turbulence Website: https://turbmodels.larc.nasa.gov/spalart.html#sa
- Please search the page for "boundary conditions", and you will see them.
- Or even better, please read the whole page - it is very good quality.

Hope it helps.

[Mateus Elias]

Thank you HPE.
To be honest, your messages don`t help. I was expecting something more practical, a way to introduce in the files U, p, nut and nuTilda.
As I am starting my journeyin OpenFoam and CFDs by now, and still working to discover how to put this boundary conditions in practice in OpenFoam.
I`ve already read this paper from NASA. It is really very good.

But I`m very thankfull for your wish to help a starting student in OpenFoam.
Regards.

[HPE]

Hi,

We don't know the physical domain that is going to be modelled - therefore, it is virtually impossible to comment on whether the boundary conditions, the only parameter determining flow behaviour in the field of interest, are viable.

Anyways.

In NASA website, for example, it states that the boundary condition for nuTilda is 0. nuTilda condition in `lowerWall` was set to `slip`. So this boundary condition you set is either wrong or correct. To determine this, we need to know what `lowerWall` is, which we don't know. If you model a wall flow, you need to set it to 0 with `fixedValue`. If you don't care what the flow should be like around `lowerWall`, `slip` condition might be OK. Yet there is a certain and crucial lack of information - so the question above is not well constructed.

Hope my example clears things out.

Thumbs up for your learning, and instead of giving negative comment on a free help here, please do consider to ask another clarifying question.