Usage of obstruction holes and obstruction overlapping

[Florian Kiersch]

Hello everyone,

I'm still new to FDS and I therefore have two questions regarding the
topics mentioned above.

First I would like to know what the correct usage of obstruction holes
would be as you can actually create holes in two ways. One way would
be to use the mentioned function and the other one would be to "build
around" your opening. As I have already seen both ways in the FDS
examples I'm wondering in which scenario each method is used
correctly.

Just to give you an idea why I'm interested: I have to recreate a
building with rooms of different (under-) pressure levels and I would
like to check different scenarios with doors opened/closed and until
now I used obstruction holes to carve out my door ways which I will
now have to close with doors. And now I'm not sure if I did it
correctly this way.

My other question is about the overlapping of obstructions such as
walls. As I did not find any information about it I would like to know
if there is any difference in creating a room with overlapping or non-
overlapping walls (corners) for example in computing time or regarding
material/surface calculations.

Best regards,
Florian Kiersch

[David Mcgill]

Hi Florian,

In my opinion, it is a bit easier when you are starting out to create
holes by leaving gaps in the obstructions and then filling them. It
doesn't make any difference if you overlap obstructions.

Dave

--
Dave McGill
School of Fire Protection
Seneca College
1750 Finch Ave E.
Toronto, ON
M2J 2X5

416-491-5050, ext, 6186

[Kevin]

Just remember the parameter PERMIT_HOLE=.FALSE. on the OBST line that
defines a door that fills a HOLE. This prevents FDS from cutting a
HOLE in the door.

In general, build a simple model of a wall and door and then ensure
that the logic to open and close the door works. This is a very common
mistake -- people create an entire building and then learn that they
have done something fundamentally wrong. Build a little test house
first.

On Nov 1, 10:09 am, Florian Kiersch <florian.kier...@googlemail.com>
wrote:

[Florian Kiersch]

Hello David, hello Kevin,

thank you very much for your fast responses. As I already created most
of the building by cutting holes I'll try to go on the way Kevin
described as I'll otherwise have to redo several walls. But for the
future I'll keep the other option in mind as well.
And regarding the doors opening and closing I already set up a test
scenario where I can try out all the new stuff and ideas without
having to run fds on the real thing. But thank you for pointing it out
as well!

Kind regards,
Florian