pressure or porous jump boundary condition
 

Dear Foamers,

Does any one know if OF supports pressure or porous jump boundary condition?

Hi,
I do not know if this is the answer to what you are looking for but...

1. a positive pressure jump can be set using the fan BC.
2. a porous jump is usually modelled using porousSimpleFoam or its variation (see here)

cheers,

mad

Thanks for reply. I'm trying to model a thin porous screen using experimental pressure loss values. I'm using porousInterfoam in which a porous zone should be defined in the computational domain. But this is not consistent with the physics. I mean the pressure loss values K=(p2-p1)/(0.5*rho*U^2) are based on a jump in the pressure and a horizontal approach velocity U in a distance from the screen. Therefore something like a pressure jump condition like in Fluent is more physical than introducing a negative source in the momentum equation that we have in OpenFoam. Apparently it is available in a non-official version of Openfoam. I'll wonder if you know where I can get that version.

Regards,
Reza

Is that not the fan bc?
What non official version are you referring? 1.6-ext? if so, it is here: http://extend-project.de/

mad

Hi,

there is a new BC in 2.0 called porousBafflepressure which looks like the one in Fluent.

Actually if you look into the code it is the same thing as in fluent. it is employed in the interFoam tutorial called damBreakwithporousbaffles.

I tried to use it in my case, by it is highly instable when coupled with a fan BC (like in fluent)

Sylvain

Hi Sylvain,

thanks for sharing the experiences.

Did you made some progress with the porousBafflepressure BC? I made similar experience with this BC: It seems to work for rather low pressure losses across the patch. But if the resistance becomes large and dominates the pressure field I didn't manage to get any stable solution. This happens also with very easy in- and outflow conditions. For my applications (filters etc.) I think I have to back to volumues zones.

Best regards

Stawrogin

sorry, may I know where is the tut for porousBafflepressure
 

is it in Openfoam 2.0.0?

I can not find it under the path: opt/openfoam200/tutorial/multiphase/interfoam/laminar...

thanks.:D

Hi Chen,

this example comes along with 2.0.x (not 2.0.1or 2.0.0) and can be found in the interFOAM ras-Dir.

You also have to add an entry for the lib to make use of this BC in your controlDict (see example case).


Stawrogin

Hi Stawrogin,


I used the porous baffles to model an heat exchanger in a wind tunnel.

It worked well, but the the flow is uniform and the pressure loss quite low at the location of the baffle.

From my previous experience in fluent, those BC are very instable, but they are very handful. So i understand your problem; I'm not familiar with the porousZone, but I think I will take a closer look at it.

Sincerely

Sylvain

Hey everyone !

I'm new on this forum and quite beginner on Openfoam.

I have exactly the same problem as described upper.
I want to simulate a pressure loss as for a filter and I try to use the porousBafflePressure BC on a simple case (for the moment).

This cas is simple, to start, with an incompressible flow, no heat transfer, one phase, etc... It's just a cylinder with a surface supposed to act as a filter.
This model works fine with the fan BC with simpleFoam but I am unable to make it work with the porousBafflePressure BC under porousSimpleFoam...

I have modified my controlDict file by adding a lib refernce as in the example of the dambreakPorousbaffle but it doesn't wotk.

My questions are :
- Do have I to use interFoam to use this porousBaffle BC, even with a so simple case ?
- If not, where can I find a detailed explanation of what to do to use it ?

Thank you very much for your answers or help !!
I used to work with Fluent or Star-CD and my first experiences with OpenFoam are very encouraging but now, I can't go further...

Laurent

Hello,

I have also been trying to use porous jump. It works well when jump values are small, but for larger value case diverges. Anyone knows what to do when pressure jump values are large?

-Yogesh

porousBafflePressure boundary condition for foam-extend-3.1
 

Hi foamers,

I would like to employ the porousBafflePressure as a boundary condition for my simulation in extended version of OpenFOAM: foam-extend-3.1. As you know this boundary condition is not available in this version, so I would like to ask if one of you has compiled the boundary condition on this version and if so, what are the requirements to consider.

Thanks for your response in advance and Best,
Mahdi

Hi,
Same problem in my case..

Anyone who could give some advices?

Regards
JW

Hi everybody,

Yes, if you prescribed a pressure jump too large the calculation is likely to explode.

My trick is too increase step by step the pressure jump ( or the inlet velocity). Once your calculation is stabilized you slightly increase the pressure jump. You iterate till you got the pressure jump you want.

You might want use the changeDictionnay tool to easily change the value of the pressure jump between each calculation.

Hope it will be useful!

Sylvain

Thank you very much!

I already tried it, but with quite large steps. I am going to try it again with smaller steps for the pressure drop. Maybe that helps :)