2D slides (velocity and CO) show values in enclosed areas where there is no air.

[javiercarlos]

Good morning,
I am having trouble running a simulation of CO extraction in a parking garage.
The initial condition is that the air must start with a CO concentration of 50 ppm, for which I have created a rectangular init region that surrounds the parking garage and assigned it 50 ppm of CO.

When I display a 3D view of the velocity, I get this result. You can see that the parking garage is not square.

But when I do the velocity or CO view in PPM at a height of 1.5m, I observe stagnant air or CO in enclosed areas (rooms and stairways enclosed by walls and ceilings), as well as air around the parking lot (external part), despite having carried out the mesh from below the solid floor to above the solid ceiling (this is because air must enter from the lower and upper ramps, as well as from the ceiling to the injection and extraction risers).

In the external areas that do not belong to the parking lot but are part of the grid, there are stains on the edges, which appear to be signs of air leakage. I have thoroughly checked the closed rooms and there are no leaks in their design; both the walls and ceilings are well sealed. That is why I do not understand why Pyrosim considers them to be full of 50 ppm from the outset or with air, when nothing should be shown in those areas. Likewise, in the areas outside the parking lot, there should be no air or CO concentration.

What could be my problem? Below is an image of a simulation that I did not do, but you can see that the ppm or velocity concentrations are only shown in the areas inside the parking lot. In my simulation, on the other hand,
the velocity and concentration planes show the entire mesh frame and not just the structure. Is this because there are air leaks in my design? How can I fix it?

I think my results should look something like this:

Thanks I solved.

[drjfloyd]

You have set:

&INIT ID='Init Region', SPEC_ID='CARBON MONOXIDE', VOLUME_FRACTION=5.0E-5, XB=0.0,49.95,0.0,39.85743,0.0,2.3/

This tells FDS to put 50 PPM into ervery gas cell in that region. This will included any closed rooms.

As to why there is no data in regions 4 + 5, you have not provided an input file corresponding to that image. Do you have MESH lines that cover those regions?

[javiercarlos]

Thank you for your response.

My leakage problem was solved when I placed a large obstruction block on that side, and regarding showing EMPTY areas, without air or concentration in the simulation planes, I solved it in two ways.

1. I used mesh cuts to try to prevent external (rectangular) areas from being displayed. However, it is impossible to eliminate triangular areas, so I converted those areas into obstructions.
2. Similarly, I converted the staircase area and closed rooms into obstructions.
3. Finally, when displaying the cutaway plans in the geometry section, I hid those obstructions and obtained a very clean presentation of my CO velocity and concentration plans.