[voingiappone]

Hello everybody,

I'm forced to ask here a very common question... already being asked many times, but I cannot realize how to get started in the right way. Please be patient.....

Situation:
I want to run a simulation in a bubble column (cylinder) with a somewhat complicated geometry. To make things easy, I started running the tutorial provided and everything goes (of course) fine. Browsing the files I realized that the p, alpha, Ua and Ub profiles are already given in the definition folder.

Problem:
In my case the fluid will be steady when I will start bubbling air in, so this definition of the variables simply doesn't work. Moreove, how can I fugure out a distribution of U,p and alpha before actually running the calculations?!?!

What I did was to purge from the files the data from the examples and correct the parameters for having a steady fluid, and a 0.1 m/s gas inlet. My config files are these.

Alpha

dimensions [0 0 0 0 0 0 0];

internalField uniform 0;

boundaryField
{
Inlet
{
type fixedValue;
value uniform 0.5;
}

Outlet
{
type fixedValue;
value uniform 0;
}

Walls
{
type zeroGradient;
}

}

pressure

dimensions [1 -1 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
Inlet
{
type zeroGradient;
}

Outlet
{
type fixedValue;
value uniform 0;
}

Walls
{
type zeroGradient;
}


}

Ua

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
Inlet
{
type fixedValue;
value uniform (0 0 0.1);
}

Outlet
{
type zeroGradient;
}

Walls
{
type fixedValue;
value uniform (0 0 0);
}


}

Ub

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
Inlet
{
type zeroGradient;
}

Outlet
{
type zeroGradient;
}

Walls
{
type fixedValue;
value uniform (0 0 0);
}


}

I'm making the fluid move along the z axis (±not like in the example, along y).

I don't know what's going on in the simulation but as I look at the results in the paraview, I see that alpha is already non-zero after 1 second almost everywhere in the column, Ua and Ub start rising in value from the top and other strange behaviours like this.

I also tried to reply wat was written in this forum post but without any luck...

I don't know what I am getting wrong even if I strongly suppose that it resides in these configuration files. If somebody could help me getting out from this....

Thank you in advance for your help

Luca