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Author Topic: Can I defy a new surface by myself?  (Read 708 times)

faker

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Can I defy a new surface by myself?
« on: August 08, 2018, 12:55:01 pm »

I did a simulation of the tunnel.Centralized smoke extraction is adopted at the top of the tunnel.The tunnel exit is set to OPEN surface,and The tunnel entrance is set to SUPPLY surface to provide additional wind speed.But natural ventilation is not allowed on the surface of SUPPLY just like OPEN.How do I get SUPPLY to provide an extra wind speed while allowing natural ventilation.Or how can I simulate induced wind speeds in tunnels?I really hope to get your help.Thank you?
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christofer.wickmark

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Re: Can I defy a new surface by myself?
« Reply #1 on: August 10, 2018, 02:16:53 am »

The WIND namelist line was introduced in FDS 6.6.0 and is described in FDS User Guide Chapter 10. However, for modelling of tunnels I would suggest the method described in FDS User Guide Chapter 9.4. Using OPEN vents where you apply a dynamic pressure to the side where the wind enters the tunnel and on the opposite side you simply keep the OPEN vent as you described. This will create an airflow from one tunnel entrance to the other. This requires a little testing if you want to achieve a specific wind speed as it depends on how large the tunnel is and so on. I have achieved a wind speed of approximately 1 m/s with a dynamic pressure of 2,6 Pa, so I suggest using that as a very rough reference.
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faker

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« Reply #2 on: September 02, 2018, 06:35:37 am »

The WIND namelist line was introduced in FDS 6.6.0 and is described in FDS User Guide Chapter 10. However, for modelling of tunnels I would suggest the method described in FDS User Guide Chapter 9.4. Using OPEN vents where you apply a dynamic pressure to the side where the wind enters the tunnel and on the opposite side you simply keep the OPEN vent as you described. This will create an airflow from one tunnel entrance to the other. This requires a little testing if you want to achieve a specific wind speed as it depends on how large the tunnel is and so on. I have achieved a wind speed of approximately 1 m/s with a dynamic pressure of 2,6 Pa, so I suggest using that as a very rough reference.
Thank you for your reply.I have another question I would like to ask you.When I used pyrosim to model curved tunnels, there were inevitably many zigzag obstacles due to grid size limitations, which made the simulation very slow.Do I have any way to simulate this model better?What is the use of "smooth" in obstruction properties?I hope I can get your help. Thank you.
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jharbold

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Re: Can I defy a new surface by myself?
« Reply #3 on: September 08, 2018, 08:45:10 am »

Perhaps look into justifying the use of a straight tunnel as opposed to incorporating the use of a non-straight model.
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