[hemph]

Hi!
I am currently modeling two-phase flow using the twoPhaseEulerFoam-application. As a boundary condition for the velocity of the dispersed phase at the outlet, I set the slip-condition. From the user manual, this boundary condition should limit the velocity normal to the face to 0, and the tangential velocity to zero gradient.

However, I get an outflow of particles/dispersed phase through this boundary!

(snip from the output log at successive time steps)
Dispersed phase volume fraction = 0.0327019 Min(alpha) = -2.2858e-31 Max(alpha) = 0.237186
Dispersed phase volume fraction = 0.0327019 Min(alpha) = -6.25311e-33 Max(alpha) = 0.237186
Dispersed phase volume fraction = 0.0326999 Min(alpha) = -2.19122e-31 Max(alpha) = 0.237179
Dispersed phase volume fraction = 0.0326999 Min(alpha) = -5.10842e-33 Max(alpha) = 0.237179
Dispersed phase volume fraction = 0.032698 Min(alpha) = -2.10048e-31 Max(alpha) = 0.237171
(/snip)

The flux of phia is of non-zero.

(example from phia-output file)
outlet
{
type calculated;
value nonuniform List<scalar>
12
(
2.93748e-10
3.68239e-10
4.54842e-10
5.29354e-10
5.82653e-10
6.10416e-10
6.10416e-10
5.82653e-10
5.29354e-10
4.54842e-10
3.68239e-10
2.93748e-10
)


It is important to the simulation that the particles stay within the domain! Am I misunderstanding something about the slip boundary condition?

Best Regards
Rasmus H