[Bessy]

Dear Foamers,
I've started to work with OpenFOAM recently in order to simulate an hydraulic jump with the interFoam solver in laminar flow (as first step).

The characteristics of the "riverbed" (rectangular section) are:
i = 0.001
B = 5 m
L = 50 m .
Creating the mesh, I divided inlet and outlet in two segments, one where I should have water and one where there should be air (as I saw it was suggested inside this forum), so the inlet height of the water is 0.1 m.

My BC are the following:

U
inlet_water
{
type fixedValue;
value uniform (2 0 0);
}
inlet_air
{
type fixedValue;
value uniform (0 0 0);
}
outlet_water
{
type fixedValue;
value uniform (0.83 0 0); //calculated in order to obtain the height of the water expected
}
outlet_air
{
type fixedValue;
value uniform (0 0 0);
}
lowerWall
{
type fixedValue;
value uniform (0 0 0);
}
atmosphere
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}

p
inlet_air
{
type zeroGradient;
}

inlet_water
{
type zeroGradient;
}

outlet_air
{
type fixedFluxPressure;
value uniform 0;
}

outlet_water
{
type fixedFluxPressure;
value uniform 0;
}

lowerWall
{
type zeroGradient;
}

atmosphere
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;
}

alpha
inlet_air
{
type fixedValue;
value uniform 0;
}

inlet_water
{
type fixedValue;
value uniform 1;
}

outlet_air
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}

outlet_water
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}

lowerWall
{
type zeroGradient;
}

atmosphere
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}

With this setting I obtain an hydraulic jump that is not stationary, indeed the hydraulic jump is pushed from downstream to upstream (please see the video of the simulation here).

I think that the problem is due to the outlet BC of the pressure. I tried also to set a different fixed value for the pressure in outlet, the one that should lead to the equilibrium between the slow and the rapid flows, but nothing changed. It seems that the software doesn't maintain my BC in outlet while doing the simulation.

Do you have any suggestion for obtaining the stationary hydraulic jump?
Thanks in advance.