wood crib reaction in fds

Mohamed Abd elkarim

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Mar 18, 2018, 10:08:12 AM3/18/18

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Hello fds users

in the simulation of burning wood crib with dimensions as attached image .

stick 3 and 5 in the bottom layer were made of fibre-board and soaked in heptane

and wood crib weight is 1.3 kg.

i draw the wood crib as s sticks obstruction

but fds show error in the the SURF cannot apply to thin obstruction !

dcdc.png

~test1.fds

Salah Benkorichi

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Mar 18, 2018, 10:23:10 AM3/18/18

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Please don't upload such big file, when you have specific issue. Try to simplify your case before uploading it as this save time for the person looking into your case. With that being said,

I have tested your case, you first need to fix the mesh alignment between each meshes. Check the mesh alignment section in user guide.

As for type of error, you seem to be using coarser mesh, on a think obst, read section 7.2.2 of user guide.

If you are going to re-upload it again, put only one single mesh, with your crib obst. Don't put all these stuff in together.

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Mohamed Abd elkarim

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Mar 18, 2018, 10:33:46 AM3/18/18

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i read User guid sec 7.22 and i have tried to writ THICKEN_OBSTRUCTIONS.TRUE in th MISC line

the result is that wood crib geometry deformed in order to prevent thin obstruction

How can i test mesh alighnment if i use one single mesh ?

On Sunday, March 18, 2018 at 4:23:10 PM UTC+2, Salah Benkorichi wrote:

Please don't upload such big file, when you have specific issue. Try to simplify your case before uploading it as this save time for the person looking into your case. With that being said,
I have tested your case, you first need to fix the mesh alignment between each meshes. Check the mesh alignment section in user guide.

As for type of error, you seem to be using coarser mesh, on a think obst, read section 7.2.2 of user guide.

If you are going to re-upload it again, put only one single mesh, with your crib obst. Don't put all these stuff in together.

On 18 March 2018 at 14:08, 'Mohamed Abd elkarim' via FDS and Smokeview Discussions <fds...@googlegroups.com> wrote:

Hello fds users
in the simulation of burning wood crib with dimensions as attached image .
stick 3 and 5 in the bottom layer were made of fibre-board and soaked in heptane
and wood crib weight is 1.3 kg.
i draw the wood crib as s sticks obstruction
but fds show error in the the SURF cannot apply to thin obstruction !

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Salah Benkorichi

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Mar 18, 2018, 10:42:40 AM3/18/18

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Upload a simple file case with one mesh that reproduce the error.

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Mohamed Abd elkarim

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Mar 18, 2018, 1:43:49 PM3/18/18

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please , knowing that wood crib made of stickes

the option "bulk density" is for single stick obstruction or for the total wood crib ??

mass of crib = 3.6 kg , volume of total crib = 0.015 m^2 , Number of sticks = 84

volume of single stick = 8.8E-5 m

which bulk density written in fds " single stick " or total sticks ??

Salah Benkorichi

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Mar 18, 2018, 3:27:38 PM3/18/18

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Well,

if you are planning to use the Bulk density on the OBST lines, then the mass will be measured based on the OBST volume multiplied by the bulk density.

&OBST ID='Obstruction', XB=0,1,0,0.1,0,0.1, SURF_ID='WOOD', BULK_DENSITY=500./

Then the mass should be 5kg.

You can use a device to track it, as the following

&DEVC XB = 0,1,0,1,0,1, QUANTITY = 'DENSITY', SPEC_ID='MY FUEL', STATISTICS = 'VOLUME INTEGRAL' ID = 'Mass fuel'/

You should also be careful with the ratio between the heat of combustion of malt and the gas phase. If HoC is specified on the MALT and REAC then, it would expect something like

5xHoC_matl/HoC_Reac

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Mohamed Ahmed

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Mar 19, 2018, 4:15:04 PM3/19/18

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In verification guide room fire.fds

&REAC FUEL = 'POLYURETHANE'

FYI = 'C_6.3 H_7.1 N O_2.1, NFPA Handbook, Babrauskas'

SOOT_YIELD = 0.10

N = 1.0

C = 6.3

H = 7.1

O = 2.1 /

SURF ID='BURNER', HRRPUA=1000., COLOR='RASPBERRY' /

&MATL ID = 'FABRIC'

FYI = 'Properties completely fabricated'

SPECIFIC_HEAT = 1.0

CONDUCTIVITY = 0.1

DENSITY = 100.0

N_REACTIONS = 1

NU_SPEC = 1.

SPEC_ID = 'POLYURETHANE'

REFERENCE_TEMPERATURE = 280.

HEAT_OF_REACTION = 1000.

HEAT_OF_COMBUSTION = 15000. /

&MATL ID = 'FOAM'

FYI = 'Properties completely fabricated'

SPECIFIC_HEAT = 1.0

CONDUCTIVITY = 0.05

DENSITY = 40.0

N_REACTIONS = 1

NU_SPEC = 1.

SPEC_ID = 'POLYURETHANE'

REFERENCE_TEMPERATURE = 300.

HEAT_OF_REACTION = 800.

HEAT_OF_COMBUSTION = 30000. /

i know that the red line is known as Heat transfere (physical ) properties and the blue line is known as Reaction characteristics (pyrolysis properties)

my issue about the blue lines , How can i get such values of REFERENCE_TEMPERATURE and HEAT_OF_REACTION for a given material ?

is it from cone calorimeter test ??

Salah Benkorichi

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Mar 19, 2018, 4:19:08 PM3/19/18

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They are properties of the material. Reference temperature works as an alternative to A and E. where A is the exponential factor and E is the energy of activation.

They represent the pyrolysis model of the material, i.e. usually taken from apparatus such. as TGA.

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From: fds...@googlegroups.com <fds...@googlegroups.com> on behalf of Mohamed Ahmed <mohamedabd...@gmail.com>
Sent: Monday, March 19, 2018 8:15:03 PM
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Subject: Re: [fds-smv] wood crib reaction in fds

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