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Author Topic: Different types of modeling fire and fire propagation  (Read 297 times)

n_moniri

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Different types of modeling fire and fire propagation
« on: May 21, 2020, 10:15:04 am »

Dear all,
I have confusion about different possible ways for modeling fire.
As I understand, we can have a fire with a burner surface and an ignitor.
what is the difference between these two options?
Thanks
« Last Edit: May 21, 2020, 10:14:48 pm by n_moniri »
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Dave McGill

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Re: Different types of modeling fire
« Reply #1 on: May 21, 2020, 01:11:12 pm »

A burner can be a vent, or the face of an obstruction. It ejects fuel. With the default simple chemistry mixing model, if the fuel mixes with oxygen in the correct proportions, then combustion will occur. This is modelled on a cell-by-cell basis. No ignition source is required.

It is possible to specify an ignition temperature for a fuel or an initialization region. In those cases, a source of heat to ignite the fuel/oxygen mixture is required. That can be supplied by an ignitor, which is essentially a hot particle, placed above the source of fuel.
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Dave McGill
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n_moniri

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Re: Different types of modeling fire
« Reply #2 on: May 21, 2020, 10:13:29 pm »

Hello Dave,
Thank you so much for your great and quick response.

I also have another confusion about the propagation of fire. I'm modeling a room with a wooden box in front of a door that is supposed to be burnt away. Also, I defined all the required information like materials of all the components, reaction, surfaces, and mesh.  Although I can see the smoke and the fire on the box, after 120s simulation I still can not see the propagation of fire. I attached my Pyrosim file to this post.

I would be appreciated if you help in this regard.
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Dave McGill

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Re: Different types of modeling fire and fire propagation
« Reply #3 on: May 22, 2020, 05:22:25 am »

Hi,

The most obvious issue is that your domain is a sealed box.
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Dave McGill
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n_moniri

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Re: Different types of modeling fire and fire propagation
« Reply #4 on: May 22, 2020, 12:06:26 pm »

Thanks Dave for your response.
By saying sealed box, you mean my model does not have any inside air flow?
If I want to address this issue I should put open vent on the wall or I should open the boundary?
When my model is imported from Revit through IFC extension to Pyrosim, does the software tool recognize that the meaning of the object? for example what is the wall or what is the door?
Thanks
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Dave McGill

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Re: Different types of modeling fire and fire propagation
« Reply #5 on: May 23, 2020, 10:23:15 am »

If you want the doors to "burn away", then you will have to have the combustion governed manually by the surface properties.

Until that happens, the room is still a sealed box. There might not be enough air in the room to support enough combustion to burn away a portion of the door.

If there is, then you need to expand the domain by a couple of meters on the side with the door on fire, and you need to put an open vent on that boundary of the domain.

I suggest you read about all of these features in the FDS Users Guide.

PyroSim recognizes that a surface has been labelled in Revit, but the surfaces created from the Revit file have no relevant properties.
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Dave McGill
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n_moniri

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Re: Different types of modeling fire and fire propagation
« Reply #6 on: June 04, 2020, 08:46:22 am »

Hello Dave,

Thank you so much for your precious guidance. The problem is solved. 
 
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