t squared fire
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Pai
Jul 27, 2009, 6:04:58 AM7/27/09
to FDS and Smokeview Discussions
I am just a new learner with regards to fds/smokeview. I have gone
through 8.5 of the user's guide.
I have an issue in getting the 't squared' fire growth curve. I have
an industrial facility with a fire load spread over a very large area
(15 m x 28 m).
I have used an HRRPUA of 250. The temperature just shoots up to a very
high value and so does the HRR. How can I get something like a 't
squared' fire growth?
I have the initial commands from the fds file;
&MISC SURF_DEFAULT='EMPTY' /
&TIME T_END=3600.0 /
&SURF ID = 'EMPTY'
MATL_ID = 'CERAMIC FIBRE'
COLOR = 'KHAKI'
THICKNESS = 0.04 /
&SURF ID = 'WALL'
MATL_ID = 'CERAMIC FIBRE'
COLOR = 'GRAY'
THICKNESS = 0.04 /
&MATL ID = 'CERAMIC FIBRE'
CONDUCTIVITY = 0.11
SPECIFIC_HEAT = 1.10
DENSITY = 700. /
&MATL ID = 'FOAM'
CONDUCTIVITY = 0.20
SPECIFIC_HEAT = 1.0
DENSITY = 20. /
&SURF ID ='BURNER'
MATL_ID ='FOAM'
HRRPUA =250.
TAU_Q =-4.61
THICKNESS =0.5
BURN_AWAY =.TRUE.
COLOR='RASPBERRY' /
&MESH IJK= 150 ,180 ,40 ,XB=-25,75,-60,60,-16.2,10.0 /
through 8.5 of the user's guide.
I have an issue in getting the 't squared' fire growth curve. I have
an industrial facility with a fire load spread over a very large area
(15 m x 28 m).
I have used an HRRPUA of 250. The temperature just shoots up to a very
high value and so does the HRR. How can I get something like a 't
squared' fire growth?
I have the initial commands from the fds file;
&MISC SURF_DEFAULT='EMPTY' /
&TIME T_END=3600.0 /
&SURF ID = 'EMPTY'
MATL_ID = 'CERAMIC FIBRE'
COLOR = 'KHAKI'
THICKNESS = 0.04 /
&SURF ID = 'WALL'
MATL_ID = 'CERAMIC FIBRE'
COLOR = 'GRAY'
THICKNESS = 0.04 /
&MATL ID = 'CERAMIC FIBRE'
CONDUCTIVITY = 0.11
SPECIFIC_HEAT = 1.10
DENSITY = 700. /
&MATL ID = 'FOAM'
CONDUCTIVITY = 0.20
SPECIFIC_HEAT = 1.0
DENSITY = 20. /
&SURF ID ='BURNER'
MATL_ID ='FOAM'
HRRPUA =250.
TAU_Q =-4.61
THICKNESS =0.5
BURN_AWAY =.TRUE.
COLOR='RASPBERRY' /
&MESH IJK= 150 ,180 ,40 ,XB=-25,75,-60,60,-16.2,10.0 /
Barbro Maria Storm
Jul 27, 2009, 7:03:32 AM7/27/09
to fds...@googlegroups.com
2009/7/27 Pai <arunp...@gmail.com>:
>
> I am just a new learner with regards to fds/smokeview. I have gone
> through 8.5 of the user's guide.
>
> I have an issue in getting the 't squared' fire growth curve. I have
> an industrial facility with a fire load spread over a very large area
> (15 m x 28 m).
>
> I have used an HRRPUA of 250. The temperature just shoots up to a very
> high value and so does the HRR. How can I get something like a 't
> squared' fire growth?
>
> I am just a new learner with regards to fds/smokeview. I have gone
> through 8.5 of the user's guide.
>
> I have an issue in getting the 't squared' fire growth curve. I have
> an industrial facility with a fire load spread over a very large area
> (15 m x 28 m).
>
> I have used an HRRPUA of 250. The temperature just shoots up to a very
> high value and so does the HRR. How can I get something like a 't
> squared' fire growth?
Try using the RAMP and RAMP_Q functions.
--
Barbro Storm
Pai
Jul 27, 2009, 7:52:59 AM7/27/09
to FDS and Smokeview Discussions
In the manual it says, if something other than a t square is required,
then a ramp function needs to be used. Even in case if I use a ramp
function, how do i determine the fracttion of heat release rate at
various times?
then a ramp function needs to be used. Even in case if I use a ramp
function, how do i determine the fracttion of heat release rate at
various times?
Kevin
Jul 27, 2009, 8:05:10 AM7/27/09
to FDS and Smokeview Discussions
The F value in RAMP is the fraction of HRRPUA. Thus, if F=0.5, you get
0.5*HRRPUA.
0.5*HRRPUA.
Pai
Jul 27, 2009, 8:25:31 AM7/27/09
to FDS and Smokeview Discussions
But instead of specifying various ramp values, is it not possible to
get the 't square' naturally? Just by the consumption of the fire laod
and oxygen.
get the 't square' naturally? Just by the consumption of the fire laod
and oxygen.
Kevin
Jul 27, 2009, 9:11:56 AM7/27/09
to FDS and Smokeview Discussions
Naturually? I'll let the fire protection engineers comment on this if
they'd like. Just show me full-scale experimental heat release rate
measurements that exhibit the t-squared behavior and then we can talk
about whether or not such behavior can be modeled "naturally."
they'd like. Just show me full-scale experimental heat release rate
measurements that exhibit the t-squared behavior and then we can talk
about whether or not such behavior can be modeled "naturally."
drjfloyd
Jul 27, 2009, 3:40:29 PM7/27/09
to FDS and Smokeview Discussions
Are you asking how to get FDS to smoothly do a t^2 fire without having
to specify a large number of RAMP lines? Search the user's guide for
TAU_Q
to specify a large number of RAMP lines? Search the user's guide for
TAU_Q
Jens
Jul 30, 2009, 6:50:02 AM7/30/09
to FDS and Smokeview Discussions
Hi Pai,
you have a real short TAU_Q time.
Your total HHR will be 105000 kW.
With an ultra fast t-squared development, this will give a growth time
on: t=sqroot(105000kW/0,19(kW/s^2))=744ss
This will result in TAU_Q=-744s, you have specified TAU_Q=-4.61 s.
I guess you have to reconsider your TAU_Q value.
regards
Jens
you have a real short TAU_Q time.
Your total HHR will be 105000 kW.
With an ultra fast t-squared development, this will give a growth time
on: t=sqroot(105000kW/0,19(kW/s^2))=744ss
This will result in TAU_Q=-744s, you have specified TAU_Q=-4.61 s.
I guess you have to reconsider your TAU_Q value.
regards
Jens
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