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Author Topic: smoke can't get out from the open surface  (Read 3343 times)

Zole Yang

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smoke can't get out from the open surface
« on: August 12, 2015, 01:01:55 am »

Hi?guys
I got a question while simulating the tunnel fire?i set a open vent at the end of the my tunnel model?i think the smoke can get through the vent?because it just act as a door or a window?but in the smokeview?smoke fall down and backflowed.
i dont understand this phenomenon,i need help,please.
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Dave McGill

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Re: smoke can't get out from the open surface
« Reply #1 on: August 12, 2015, 04:30:45 am »

Hi Zole,

Can you supply the input file?

Dave
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Dave McGill
firemodel.ca

Zole Yang

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Re: smoke can't get out from the open surface
« Reply #2 on: August 12, 2015, 06:59:21 pm »

Hi Zole,

Can you supply the input file?

Dave
Hi Dave.
this is my model.Thanks for your help .
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Dave McGill

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Re: smoke can't get out from the open surface
« Reply #3 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
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Dave McGill
firemodel.ca

Zole Yang

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Re: smoke can't get out from the open surface
« Reply #4 on: August 13, 2015, 08:08:04 pm »

Morning,Dave.
How did you modify the model?
Can you put some pictures about the smoke flow through the open vent in your simulation?
I need to solve this problem,i tried but i didn't work.
Or,can you tell me how to simulate the tunnel fire ,the boundary condition,maybe some profiles,or books,anything will help.
Thanks very much.
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Dave McGill

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Re: smoke can't get out from the open surface
« Reply #5 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
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Dave McGill
firemodel.ca

Dave McGill

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Re: smoke can't get out from the open surface
« Reply #6 on: August 14, 2015, 03:24:11 pm »

Here's an image at 118 s showing the smoke venting.
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Dave McGill
firemodel.ca

Zole Yang

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Re: smoke can't get out from the open surface
« Reply #7 on: August 16, 2015, 07:24:04 pm »

Hi,Dave.
Thanks for help,it works and i know how to fix my model.
Have a good day.
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