Porous surfaces

[iker23]

Hi group!!

I have been reading de User guide Searching something about porous
surfaces, and if is posible to create a surface with a prosity degree.
I want to say that if it is posible to create an obstruction without
holes and if it is possible that the smoke crosses across it because
the obstruction have porosity degree.

this is a image to understand better:

___
------------->| |----->
------------->| |----->
------------->| |-----> 10% SMOKE
------------->|__|----->
100% obst
SMOKE


REGARDS

[dr_jfloyd]

Not currently, but it is a good idea and as we attempt to extend the
current framework to deal with more soot physics it is something to
keep in mind. Please post your idea to the issue tracker as an
enhancement request so we have a reminder of it.

[iker23]

I'VE JUST POSTED THIS COMENT IN THE ISSUE TRACKER BUT I DON´T KNOW HOW
TO POST AS AN ENHACEMENT REQUEST AND I POSTED IT AS AN ISSUE, CAN YOU
POST AS AN ENHACEMENT PLEASE?

THANKS A LOT

REGARDS!!

[dr_jfloyd]

thanks.

[kok leong chin]

This is really a good idea as I think lot of user want to have this option. I will bring the simulation more realistic to some perforated surface.

[Randy McDermott]

I wanted to point out that the formulation Ruddy Mell uses for his
wildland fire simulations (http://www2.bfrl.nist.gov/userpages/wmell/
public.html) can already handle this by using what we call a "Material
Point Method"... Lagrangian particles are used in place of obstacles
and these particles possess properties such as: position, velocity
(zero for an obstacle), volume, projected area, porosity, etc. These
particles can be linked together via Hookean force laws to model
structural mechanics and they interact with the fluid via drag laws
and momentum source terms. Tentative plans are to incorporate this
formulation more generally in FDS 6.0.

On Dec 23, 12:21 pm, "kok leong chin" <kokleo...@gmail.com> wrote:
> This is really a good idea as I think lot of user want to have this option.
> I will bring the simulation more realistic to some perforated surface.
>

[Hostikka Simo]

Randy, would it be somehow possible to take into account the actual volume of the particles
and thus the effect on pressure field?

Simo

> > > > > > ------------->|    |----->   10% SMOKE __|----->
> > > > > >  100%      obst
> > > > > > SMOKE
> >
> > > > > > REGARDS
> >
> >
> >
>

[fde]

Updating an old discussion. 

I was reading the part 15.4.8 Screens, in the example, a 0.0003 m wire diameter mesh is given. However, THICKNESS in SURF line is 0.00015 m. I do not understand why are they not the same.

A second point, since it is now possible to model a porous screen with particles for pressure drop, would it be possible in the future to adopt a function for these screens to act as radiation screens?

[Kevin]

THICKNESS is the wire radius.

[Kevin]

Back to the larger discussion, the use of Lagrangian particles to mimic the action of a screen works OK for relatively open screens. As the porosity decreases, the current algorithm becomes unstable. We see this in the few verification cases. The problem has to do with the interaction of the pressure solver and the large drag term necessary to create a barrier of low porosity. As the porosity goes to zero, in theory the flow should to, but there is no mechanism for this in the model.

I think we should use the HVAC machinery to make this transition more smoothly.

[fde]

 Thank you for the reply. 

[dr_jfloyd]

It should be possible to include radiation. If you open a feature request on the issue tracker we can continue the discussion there.

On Tuesday, January 9, 2018 at 4:27:47 AM UTC-5, fde wrote: