[keepfit]

Dear Foamers,

I want to make a simple dam break test with a lifting gate. The gate is lifted with a velocity of 0.5 m/s at Z+ direction. I was wondering if it is possible to realize this without dynamic mesh.



The gate could be implemented as a zero thickness wall or baffle in OpenFOAM, the problem is that, how to "move" this baffle according to the lifting velocity without using dynamic mesh, since all we need is to set some fixed internal faces as walls.

The first idea comes to my mind is that: at every 0.1 sec, use the "createBaffles" command to update the gate position. But the baffle can only be created once at the beginning, do we have any method to change these faces that consist of the gate baffle?

Any idea?

Best regards,

David

[wyldckat]

Quick answer: Without dynamic mesh, then:

1. The baffle cannot move on its own. At least the top will never move.
2. The closest you can have is an effect similar to it dissolving. This can be done with a "porous baffle". Google:
   

   openfoam "porousBaffle*"

3. The problem is that currently there isn't one in OpenFOAM that is able to do change the porous values in function of height and time. You will have to code one yourself, where the Darcy coefficients change in function of height and time, where the height is also in function of time.

[zfaraday]

Maybe activeBaffleVelocity may help you, although I am not sure about it... Here you can find a little bit of information.

Best regards,

Alex

[wyldckat]

Hi Alex,

Originally Posted by zfaraday

Maybe activeBaffleVelocity may help you, although I am not sure about it... Here you can find a little bit of information.

I thought about that as well, but that boundary condition requires a special PDR mesh, which only PDRFoam uses at the moment.

Either way, a new boundary condition will have to be coded.

Best regards,
Bruno

[zfaraday]

Originally Posted by wyldckat

Hi Alex,

I thought about that as well, but that boundary condition requires a special PDR mesh, which only PDRFoam uses at the moment.

Either way, a new boundary condition will have to be coded.

Best regards,
Bruno

I don't even know what a PDR mesh is... :P


By the way, maybe groovyBC has something to say about this problem! Just to avoid the hard work of coding a whole new BC... However, if it was possible I have no clue on how to do it...

[wyldckat]

Originally Posted by zfaraday

I don't even know what a PDR mesh is... :P

The one example that uses the PDR mesh is "activePressureForceBaffleVelocity"... I studied it sometime ago for fixing a bug: http://www.openfoam.org/mantisbt/view.php?id=1793#c5281 - the one you mentioned, namely "activeBaffleVelocity", is a simpler form of this boundary condition.

[keepfit]

Originally Posted by wyldckat

Hi Alex,

I thought about that as well, but that boundary condition requires a special PDR mesh, which only PDRFoam uses at the moment.

Either way, a new boundary condition will have to be coded.

Best regards,
Bruno

Originally Posted by zfaraday

Maybe activeBaffleVelocity may help you, although I am not sure about it... Here you can find a little bit of information.

Best regards,

Alex

Thanks @wyldckat and @zfaraday for the tips, it seems that its not an easy task. If the dynamic mesh is used in this case, does the faceID, CellID change over time? since the zero-thickness baffle is moving vertically.

I could not find any example with "activeBaffleVelocity" BC in tutorials folder, nor in the OpenFOAM forum. It would be great if someone can give some advice on how to use this BC.

Can we first use Createbaffles to create the gate, and then apply activeBaffleVelocity BC like this:

Gate
{
	type     activeBaffleVelocity;
	p      p;
	cyclicPatch     myCyclic;  // change the position
	orientation     -1;
	openFraction     0.2;
	openingTime     0.05;
	maxOpenFractionDelta     0.1;
}

As for the porousBafflePressure BC, how can we change some properties of this BC over time? For example to increase the permeability at the bottom with a very high value to mimic the opening.

[Bodo1993]

Hello David,
I am wondering if you figured out a way to solve your problem without dynamic meshing. Thanks.

[uosilos]

Originally Posted by wyldckat

Hi Alex,

I thought about that as well, but that boundary condition requires a special PDR mesh, which only PDRFoam uses at the moment.

Either way, a new boundary condition will have to be coded.

Best regards,
Bruno

Hi Bruno,


Can't activePressureForceBaffleVelocity be used with a "normal" mesh, for instance one imported .msh??

[mrozki]

Hi foamers,

Did anyone managed to do a dam-break in openFoam and controling the gate velocity lifting ?