Questions about the inletOutlet and outletInlet boundary conditions

 Register Blogs Members List Search Today's Posts Mark Forums Read

Rate this Entry

Questions about the inletOutlet and outletInlet boundary conditions

Posted August 2, 2011 at 22:27 by tfuwa

Quote:
Originally Posted by Fransje
Ok.

Let's try to explain inflowOutflot and outflowInflow simply. Let's consider the following code:
Code:
```U:
outlet
{
type inletOutlet;
inletValue uniform (-2 0 0);
value (0 0 0);
}```
With this boundary condition, we have that:
• If the velocity vector at the outlet points out of the domain, then the boundary condition will be of the Neumann type, ie, zeroGradient.
• If the velocity vector points into the domain, then we can imagine that the outflow is no longer an outflow, but an inflow, and that we therefore would like to specify a Dirichlet boundary condition, ie, with constant value. In our case the boundary condition would take the value (-2 0 0), ie, Ux = -2, Uy = 0, Uz = 0.
From what I've read, the value (0 0 0) option is a dummy option needed for paraFoam/paraview and should not further be considered. Please correct me if I'm wrong.

Similarly, if, for some reason, we were to specify:
Code:
```k:
outlet
{
type outletInlet;
outletValue uniform 5;
value 0;
}```
we would have that
• If the velocity vector at the outlet was to point out of the domain, then the boundary condition would be of the Dirichlet type, with value 5.
• If the velocity vector at the outlet was to point into the domain, then the outflow conditions would switch from fixedValue to zeroGradient, and become a Neumann boundary condition.

this seems very good.
Posted in Uncategorized