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Messages - Dave McGill

Pages: 1 [2] 3 4 ... 9
16
PyroSim / Re: steady fire
« on: September 02, 2015, 07:44:09 am »
Hi Tricia,

I changed your cell size to an even 0.2 m and created 4 meshes. It's running fine for me. The revised file is here.

https://www.dropbox.com/s/y17agojhdcdcjug/Canopy600mm_rev1.psm?dl=0

Dave

17
PyroSim / Re: steady fire
« on: September 01, 2015, 04:53:21 am »
Hi Tricia,

It's hard to diagnose without having the input file. Can you put it on Dropbox?

Dave

18
PyroSim / Re: Smoke Layer Not Descending Past 3 Meters
« on: August 27, 2015, 08:53:32 am »
Hi,

There are a couple of issues at play here. This is reflecting a change in the default settings for Smokeview.

In PyroSim, you can create all sorts of fancy geometry, such as the angled walls in your model. It is also possible to import very complex geometry from REVIT or 3D CAD files.  What you see in PyroSim may not have a very tenuous connection with what is built and modelled in FDS. When a file is exported from PyroSim, the details of the complex geometry are contained in the file jobname.ge1. In the the past, this information was not shown in Smokeview unless it was explicitly loaded (Show/HIde -> Geometry -> Obstacles -> CAD). It is now loaded by default, and can be turned off with the "q" key.

When you load your file the geometry looks like what you saw in PyroSim, but which is not what was modelled. Load up your model in Smokeview and hit the "q" key. Note how the angled walls change to a "stair-step" appearance and the door disappears. The latter reflects the width of the door hole and the cell size used in that area. So, the model you ran does not have a door, and your fire is in a sealed box.

See the attached file with a new door that spans two cells, and the wall.

Dave

19
PyroSim / Re: Fire in Duct
« on: August 18, 2015, 10:39:33 am »
You could use 2D obstructions to create a duct, and put a fan in it. You would need small cells to resolve what was happening in the duct.

Check out the example files that came with the FDS 6 install. I know at least one of the HVAC examples has a duct/ fan shroud created out of 2D obstructions.

20
PyroSim / Re: smoke can't get out from the open surface
« on: August 14, 2015, 03:24:11 pm »
Here's an image at 118 s showing the smoke venting.

21
PyroSim / Re: smoke can't get out from the open surface
« on: August 14, 2015, 10:39:17 am »
Hi Zole,

I think it was working, after a fashion. Your tunnel fire is an unusual situation, as there is a very deep smoke layer that almost fills the tunnel as it progress along the tunnel. I think what is shown in your images is part of the smoke being entrained by the flow of fresh air into the tunnel at floor level.

There is another issue in that the openings to the tunnel are at the boundary of the domain. See the discussion on Open Vents in section 7.3.2 of the FDS Users Guide. It is recommended that openings be several meters from the open boundary of the domain.

I've modified you file to add a mesh at either end of the tunnel, and also added a velocity slice file down the middle of the tunnel. By looking at the slice file, it is clear that air is flowing both in and out of the tunnel. See the attached file and images. The smoke has not yet reached the mouth of the tunnel, and I will post some more images when it does.

Dave

22
PyroSim / Re: smoke can't get out from the open surface
« on: August 13, 2015, 12:55:47 pm »
Hi Zole,

I simplified the file, and the OPEN vent did work. I'm not sure why it is not working in your example. I'll let you know, if and when I figure it out.

Dave

23
PyroSim / Re: smoke can't get out from the open surface
« on: August 12, 2015, 04:30:45 am »
Hi Zole,

Can you supply the input file?

Dave

24
PyroSim / Re: Fire in Duct
« on: August 06, 2015, 07:27:52 am »
If you are referring to a duct that is an HVAC element, then it can't be done. (As an aside, anything entering a node at one end of a duct immediately appears at the other end of the duct; there is no transit time in the duct.)

Dave

25
PyroSim / Re: Video Capability
« on: July 30, 2015, 07:18:55 pm »
PyroSim doesn't, but Smokeview does.

See chapter 13 of the Smokeview Users Guide. It will show you how to take a series of snapshots, and then stitch them into a movie with some open source software. (You have to download and install the software first.)

Dave

26
The quick answer is yes. (This can be done in Smokeview, I can't confirm that the slice file can be imported successfully into Pathfinder.)

I sometimes do that to illustrate a visibility cut-off. As I recall, the trick is something like this.
- in Smokeview select  Show/hide -> data coloring -> colorbars -> Black - white
- in Smokeview select  Show/hide -> data coloring ->flip
- Dialogs -> file/bound, set the minimum to what ever you want

Everything above the minimum will appear black.



Dave

27
PyroSim / Re: Importing DWG/DXF File
« on: July 02, 2015, 09:31:16 am »
What's the ratio of L:W:H in the building? The dimensions in your screen capture suggest 1:1:30, which is very odd, unless it's a tower.

Dave

28
PyroSim / Re: Quantifying HRR & Air Intake Flowrates
« on: July 02, 2015, 09:11:56 am »
Hi,

The easiest thing is to check the jobname_hrr.csv file, which is created automatically. If it indicates that you are still getting a lower value than you think you should get, then make sure there is an adequate air supply, and/or try a finer mesh.

Dave

29
PyroSim / Re: Difficulty modelling sprinkler actuation times
« on: June 10, 2015, 05:25:03 pm »
I think there are two issues at play.

1.  The domain is a sealed box, so a normal plume that entrains cool air and displaces the hot, less dense air to the top of the domain is not occurring.

2. The grid is too coarse.

I simplified your model into a fire, a sprinkler link, a ceiling, and open sides. I ran it with cells sizes of: 2 m, 1 m, 0,5 m, and 0.25 m. I plotted the sprinkler link temperatures.

See the graph. The temperatures converge, and indicate that a cell size of 0.5 m, or less, is required, along with a domain that is not a sealed box.

The graph and the PyroSim files can be downloaded from dropbox.

https://www.dropbox.com/sh/927zseah74zvcxz/AAAMS3oNR9A33kEVR2EWbj6Ia?dl=0

Dave

30
PyroSim / Re: Difficulty modelling sprinkler actuation times
« on: June 09, 2015, 06:26:05 pm »
It's a 10 MW fire with a growth ramp. How big is the fire when the first sprinkler goes off? With that ceiling height, I would expect the sprinklers to go off when the fire is at least several MW in size. The cell size is very coarse. Keep cutting your cell size in 1/2 and see if the activation times converge.

Dave

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