Teething Problems

[MrBing]

Hello all

I'm currently undertaking a project of modelling a 9.1MW fire in a retail building with performance based smoke exhaust vents in the roof. The model was built quickly with pyrosim, however if have encountered some problems when running it with FDS.


1. I drew a flat roof with holes for the vents, however i kept getiing an error message saying the vents (smoke exhaust fan) needed to be attached to a solid surface? Should i not have placed the holes in the roof or just provided the smoke exhaust vents alone?

2. When i ran thee model the fire does appear to be working correctly, and i can't see the smoke movement in smoke view.

3. i added a slice file at z = 2.1m for measusrement of smoke layer, but its not giving me correct outputs.

4. Is it possible to have the roof invisible for the scenario in smoke view???



The building is pretty big, it is possible the the model is not working due to the overall size of the building itself?? I have enclosed the file for some feedback.

[Charlie Thornton]

Which version of FDS are you using? I'm using FDS 5.5.3 x64 (serial) rev 7031.

When I try to run the model you attached, it complains that "WARNING: Two VENTs overlap in MESH 1, Cell 101 82 0 . VENT 2 rejected for that cell" (repeated for a total of 16 times). I think this is because the fire vent is on the same plane as the floor vent. You may be able to get rid of the "floor" vent altogether.

For your exhaust vents: It looks like right now you've got that big OPEN vent across the top. There are also some solids that have been canceled out by some holes. Were these solid chucks previously the obstructions to which you attached your exhaust vents? If that's the case, the most common cause of your problem is that the place where the vent was supposed to meet the obstruction did not lie along a grid cell boundary and the vent resolved to a different place than the obstruction (causing them to not be pressed together in the simulator).

I'm hoping questions 2 and 3 fix themselves when you get your vent issues resolved.

To make any vent or obstruction invisible in Smokeview: right-click the object in the tree, then click Hide Object(s).

[MrBing]

For your exhaust vents: It looks like right now you've got that big OPEN vent across the top. There are also some solids that have been canceled out by some holes. Were these solid chucks previously the obstructions to which you attached your exhaust vents? If that's the case, the most common cause of your problem is that the place where the vent was supposed to meet the obstruction did not lie along a grid cell boundary and the vent resolved to a different place than the obstruction (causing them to not be pressed together in the simulator).

I'm hoping questions 2 and 3 fix themselves when you get your vent issues resolved.

To make any vent or obstruction invisible in Smokeview: right-click the object in the tree, then click Hide Object(s).

The chunks in the air were the holes i made in the roof ostruction above the vents, i'll give it another go, thanks for your help.

Its running better now that the floor is gone