Burning of wood crib.

[Minku]

Dear sir,

I am new in FDS, i am trying to burn wood cib, to burn wood crib it have placed burner at the bottom of crib say HRRUPA 500 kW/m2.
Wood crib is burning and disappearing also. but the problem is that but i am not getting proper HRR curve instead for whole simulation time HRR shows in result is constant that means no effect of wood burning i am getting.

thanks you sir in advance.
waiting for u r positive response.

[palinda bandara]

Dear Minku

I am also new to FDS. Anyway can I have a look at your input file?

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[Minku]

Dear sir,
pls hav a look on FDS input fire.latest_woodcrib.fds
Generated by PyroSim - Version 2011.1.1219
Dec 4, 2012 10:20:33 PM

&HEAD CHID='latest_woodcrib', TITLE='woodcrib'/
&TIME T_END=1200.0, DT=5.0, RESTRICT_TIME_STEP=.FALSE./
&DUMP RENDER_FILE='latest_woodcrib.ge1', DT_RESTART=300.0/
&MISC TMPA=25.0/

&MESH ID='Room', IJK=60,81,60, XB=0.0,4.0,-1.5,4.0,0.0,4.0/

&REAC ID='WOOD',
      FYI='NFPA Babrauskas',
      C=3.4,
      H=6.2,
      O=2.5,
      N=0.0,
      HRRPUA_SHEET=600.0,
      IDEAL=.TRUE.,
      HEAT_OF_COMBUSTION=1.4025E4,
      CO_YIELD=0.00435655,
      SOOT_YIELD=0.1,
      MASS_EXTINCTION_COEFFICIENT=7600.0/

&MATL ID='YELLOW PINE',
      FYI='Quintiere, Fire Behavior - NIST NRC Validation',
      SPECIFIC_HEAT=2.85,
      CONDUCTIVITY=0.14,
      DENSITY=640.0,
      HEAT_OF_COMBUSTION=1.4025E4/
&MATL ID='GYPSUM',
      FYI='NBSIR 88-3752 - ATF NIST Multi-Floor Validation',
      SPECIFIC_HEAT=1.09,
      CONDUCTIVITY=0.17,
      DENSITY=930.0/

&SURF ID='WOOD',
      RGB=146,202,166,
      TEXTURE_MAP='psm_spruce.jpg',
      TEXTURE_WIDTH=0.67056,
      TEXTURE_HEIGHT=2.4384,
      BURN_AWAY=.TRUE.,
      BACKING='EXPOSED',
      MATL_ID(1,1)='YELLOW PINE',
      MATL_MASS_FRACTION(1,1)=1.0,
      THICKNESS(1)=0.015/
&SURF ID='GYPSUM',
      COLOR='GRAY 80',
      MATL_ID(1,1)='GYPSUM',
      MATL_MASS_FRACTION(1,1)=1.0,
      THICKNESS(1)=0.013/
&SURF ID='ADIABATIC',
      COLOR='GRAY 80',
      ADIABATIC=.TRUE./
&SURF ID='BURNER',
      COLOR='RED',
      TEXTURE_MAP='psm_fire.jpg',
      HRRPUA=681.6/

&OBST XB=1.75,1.8,1.75,2.25,0.301,0.316, SURF_ID='WOOD'/ CS 1
&OBST XB=2.2,2.25,1.75,2.25,0.301,0.316, SURF_ID='WOOD'/ CS 1
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1
&OBST XB=1.675,2.325,1.675,2.325,0.3,0.301, SURF_ID='INERT'/ Obstruction
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2]
&OBST XB=1.75,2.25,2.11,2.16,0.316,0.331, SURF_ID='WOOD'/ CS 1[4]
&OBST XB=1.75,2.25,2.2,2.25,0.316,0.331, SURF_ID='WOOD'/ CS 1[5]
&OBST XB=1.75,2.25,1.75,1.8,0.346,0.361, SURF_ID='WOOD'/ CS 1[1]
&OBST XB=1.75,2.25,1.75,1.8,0.376,0.391, SURF_ID='WOOD'/ CS 1[2]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[3]
&OBST XB=1.75,2.25,1.75,1.8,0.406,0.421, SURF_ID='WOOD'/ CS 1[4]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[5]
&OBST XB=1.75,2.25,1.75,1.8,0.436,0.451, SURF_ID='WOOD'/ CS 1[6]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[7]
&OBST XB=1.75,2.25,1.75,1.8,0.466,0.481, SURF_ID='WOOD'/ CS 1[8]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[9]
&OBST XB=1.75,2.25,1.75,1.8,0.496,0.511, SURF_ID='WOOD'/ CS 1[10]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[11]
&OBST XB=1.75,2.25,1.75,1.8,0.526,0.541, SURF_ID='WOOD'/ CS 1[12]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[13]
&OBST XB=1.75,2.25,1.75,1.8,0.316,0.331, SURF_ID='WOOD'/ CS 1[14]
&OBST XB=1.75,2.25,1.93,1.98,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][1]
&OBST XB=1.75,1.8,1.75,2.25,0.316,0.331, SURF_ID='WOOD'/ CS 1[1]
&OBST XB=1.75,1.8,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2]
&OBST XB=1.75,1.8,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[3]
&OBST XB=1.75,1.8,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[4]
&OBST XB=1.75,1.8,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[5]
&OBST XB=1.75,1.8,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[6]
&OBST XB=1.75,1.8,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[7]
&OBST XB=1.75,1.8,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[7][1]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1]
&OBST XB=1.75,2.25,2.2,2.25,0.376,0.391, SURF_ID='WOOD'/ CS 1[5][2]
&OBST XB=1.75,2.25,2.2,2.25,0.406,0.421, SURF_ID='WOOD'/ CS 1[5][3]
&OBST XB=1.75,2.25,2.2,2.25,0.436,0.451, SURF_ID='WOOD'/ CS 1[5][4]
&OBST XB=1.75,2.25,2.2,2.25,0.466,0.481, SURF_ID='WOOD'/ CS 1[5][5]
&OBST XB=1.75,2.25,2.2,2.25,0.496,0.511, SURF_ID='WOOD'/ CS 1[5][6]
&OBST XB=1.75,2.25,2.2,2.25,0.526,0.541, SURF_ID='WOOD'/ CS 1[5][7]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1][1]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1][2]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1][3]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1][4]
&OBST XB=1.75,2.25,2.2,2.25,0.346,0.361, SURF_ID='WOOD'/ CS 1[5][1][5]
&OBST XB=1.75,2.25,1.84,1.89,0.345,0.36, SURF_ID='WOOD'/ CS 1[2][2]
&OBST XB=1.75,2.25,1.84,1.89,0.375,0.39, SURF_ID='WOOD'/ CS 1[2][3]
&OBST XB=1.75,2.25,1.84,1.89,0.405,0.42, SURF_ID='WOOD'/ CS 1[2][4]
&OBST XB=1.75,2.25,1.84,1.89,0.435,0.45, SURF_ID='WOOD'/ CS 1[2][5]
&OBST XB=1.75,2.25,1.84,1.89,0.465,0.48, SURF_ID='WOOD'/ CS 1[2][6]
&OBST XB=1.75,2.25,1.84,1.89,0.495,0.51, SURF_ID='WOOD'/ CS 1[2][8]
&OBST XB=1.75,2.25,1.84,1.89,0.525,0.54, SURF_ID='WOOD'/ CS 1[2][9]
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][10]
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][11]
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][12]
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][13]
&OBST XB=1.75,2.25,1.84,1.89,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][14]
&OBST XB=1.75,2.25,1.93,1.98,0.346,0.361, SURF_ID='WOOD'/ CS 1[2][1][1]
&OBST XB=1.75,2.25,1.93,1.98,0.376,0.391, SURF_ID='WOOD'/ CS 1[2][1][2]
&OBST XB=1.75,2.25,1.93,1.98,0.406,0.421, SURF_ID='WOOD'/ CS 1[2][1][3]
&OBST XB=1.75,2.25,1.93,1.98,0.436,0.451, SURF_ID='WOOD'/ CS 1[2][1][4]
&OBST XB=1.75,2.25,1.93,1.98,0.466,0.481, SURF_ID='WOOD'/ CS 1[2][1][5]
&OBST XB=1.75,2.25,1.93,1.98,0.496,0.511, SURF_ID='WOOD'/ CS 1[2][1][6]
&OBST XB=1.75,2.25,1.93,1.98,0.526,0.541, SURF_ID='WOOD'/ CS 1[2][1][7]
&OBST XB=1.75,2.25,1.93,1.98,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][1][8]
&OBST XB=1.75,2.25,1.93,1.98,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][1][9]
&OBST XB=1.75,2.25,1.93,1.98,0.316,0.331, SURF_ID='WOOD'/ CS 1[2][1][10]
&OBST XB=1.75,2.25,2.02,2.07,0.346,0.361, SURF_ID='WOOD'/ CS 1[3][1]
&OBST XB=1.75,2.25,2.02,2.07,0.376,0.391, SURF_ID='WOOD'/ CS 1[3][2]
&OBST XB=1.75,2.25,2.02,2.07,0.316,0.331, SURF_ID='WOOD'/ CS 1[3][4]
&OBST XB=1.75,2.25,2.02,2.07,0.406,0.421, SURF_ID='WOOD'/ CS 1[3][5]
&OBST XB=1.75,2.25,2.02,2.07,0.436,0.451, SURF_ID='WOOD'/ CS 1[3][6]
&OBST XB=1.75,2.25,2.02,2.07,0.466,0.481, SURF_ID='WOOD'/ CS 1[3][7]
&OBST XB=1.75,2.25,2.02,2.07,0.496,0.511, SURF_ID='WOOD'/ CS 1[3][8]
&OBST XB=1.75,2.25,2.02,2.07,0.526,0.541, SURF_ID='WOOD'/ CS 1[3][3]
&OBST XB=1.75,2.25,2.11,2.16,0.346,0.361, SURF_ID='WOOD'/ CS 1[4][1]
&OBST XB=1.75,2.25,2.11,2.16,0.376,0.391, SURF_ID='WOOD'/ CS 1[4][2]
&OBST XB=1.75,2.25,2.11,2.16,0.406,0.421, SURF_ID='WOOD'/ CS 1[4][3]
&OBST XB=1.75,2.25,2.11,2.16,0.436,0.451, SURF_ID='WOOD'/ CS 1[4][4]
&OBST XB=1.75,2.25,2.11,2.16,0.466,0.481, SURF_ID='WOOD'/ CS 1[4][5]
&OBST XB=1.75,2.25,2.11,2.16,0.496,0.511, SURF_ID='WOOD'/ CS 1[4][6]
&OBST XB=1.75,2.25,2.11,2.16,0.526,0.541, SURF_ID='WOOD'/ CS 1[4][7]
&OBST XB=2.2,2.25,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2]
&OBST XB=2.2,2.25,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[3]
&OBST XB=2.2,2.25,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[4]
&OBST XB=2.2,2.25,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[5]
&OBST XB=2.2,2.25,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[6]
&OBST XB=2.2,2.25,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[7]
&OBST XB=2.2,2.25,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[1][2]
&OBST XB=2.2,2.25,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[1][3]
&OBST XB=2.2,2.25,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[1][4]
&OBST XB=2.2,2.25,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[1][5]
&OBST XB=2.2,2.25,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[1][6]
&OBST XB=1.84,1.89,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][1]
&OBST XB=1.93,1.98,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][2]
&OBST XB=2.02,2.07,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][3]
&OBST XB=2.11,2.16,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][4]
&OBST XB=1.75,1.8,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][6]
&OBST XB=1.75,1.8,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][7]
&OBST XB=1.84,1.89,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2][1][1]
&OBST XB=1.84,1.89,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[2][1][2]
&OBST XB=1.84,1.89,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[2][1][3]
&OBST XB=1.84,1.89,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[2][1][4]
&OBST XB=1.84,1.89,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[2][1][5]
&OBST XB=1.84,1.89,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[2][1][6]
&OBST XB=1.84,1.89,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][1][7]
&OBST XB=1.84,1.89,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][1][8]
&OBST XB=1.93,1.98,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2][2][1]
&OBST XB=1.93,1.98,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[2][2][2]
&OBST XB=1.93,1.98,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[2][2][3]
&OBST XB=1.93,1.98,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[2][2][4]
&OBST XB=1.93,1.98,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[2][2][5]
&OBST XB=1.93,1.98,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[2][2][6]
&OBST XB=1.93,1.98,1.75,2.25,0.331,0.346, SURF_ID='WOOD'/ CS 1[2][2][7]
&OBST XB=2.02,2.07,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2][3][1]
&OBST XB=2.02,2.07,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[2][3][2]
&OBST XB=2.02,2.07,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[2][3][3]
&OBST XB=2.02,2.07,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[2][3][4]
&OBST XB=2.02,2.07,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[2][3][5]
&OBST XB=2.02,2.07,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[2][3][6]
&OBST XB=2.02,2.06,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2][3][7]
&OBST XB=2.11,2.16,1.75,2.25,0.361,0.376, SURF_ID='WOOD'/ CS 1[2][4][1]
&OBST XB=2.11,2.16,1.75,2.25,0.391,0.406, SURF_ID='WOOD'/ CS 1[2][4][2]
&OBST XB=2.11,2.16,1.75,2.25,0.421,0.436, SURF_ID='WOOD'/ CS 1[2][4][3]
&OBST XB=2.11,2.16,1.75,2.25,0.481,0.496, SURF_ID='WOOD'/ CS 1[2][4][4]
&OBST XB=2.11,2.16,1.75,2.25,0.511,0.526, SURF_ID='WOOD'/ CS 1[2][4][5]
&OBST XB=2.11,2.16,1.75,2.25,0.451,0.466, SURF_ID='WOOD'/ CS 1[2][4][3][1]
&OBST XB=0.0,4.0,0.0,0.2,0.0,4.0, SURF_ID='GYPSUM'/ Wall
&OBST XB=1.8,2.2,1.8,2.2,0.0,0.3, SURF_ID='INERT'/ Obstruction

&HOLE XB=1.5,2.5,0.0,0.2,0.0,2.0/ Door

&VENT SURF_ID='BURNER', XB=1.75,2.25,1.75,2.25,0.316,0.316/ Burner
&VENT SURF_ID='ADIABATIC', XB=0.0,0.0,0.0,4.0,0.0,4.0/ Vent
&VENT SURF_ID='ADIABATIC', XB=4.0,4.0,0.0,4.0,0.0,4.0/ Vent[1]
&VENT SURF_ID='ADIABATIC', XB=0.0,4.0,4.0,4.0,0.0,4.0/ Vent[2]
&VENT SURF_ID='ADIABATIC', XB=0.0,4.0,0.0,4.0,4.0,4.0/ Vent[3]
&VENT SURF_ID='OPEN', XB=0.0,0.0,-1.5,0.0,0.0,4.0/ Vent
&VENT SURF_ID='OPEN', XB=4.0,4.0,-1.5,0.0,0.0,4.0/ Vent[1]
&VENT SURF_ID='OPEN', XB=0.0,4.0,-1.5,0.0,4.0,4.0/ Vent[2]
&VENT SURF_ID='OPEN', XB=0.0,4.0,-1.5,-1.5,0.0,4.0/ Vent[3]

&BNDF QUANTITY='BURNING RATE'/
&BNDF QUANTITY='NORMAL VELOCITY'/
&BNDF QUANTITY='RADIATIVE HEAT FLUX'/

&SLCF QUANTITY='MIXTURE FRACTION', PBX=2.0/
&SLCF QUANTITY='TEMPERATURE', PBX=2.0/
&SLCF QUANTITY='VELOCITY', VECTOR=.TRUE., PBX=2.0/


&TAIL /

[Dave McGill]

Hello Minku,

The wood crib is built with a repeating dimension of 0.015 m. It looks very nice in PyroSim. However, the mesh of your FDS model has a cell size of 0.07 m. If you look at the model in Smokeview, it doesn't have the resolution of what you have built in PyroSim. You will either have to make the pieces of the wood crib much bigger, or make the cell size much smaller. One way or another, the two have to be on the same grid.

I don't think the crib is burning away. The gaps seem in Smokeview are due to the OBSTs aligning with the cell dimensions.  I think this is also resulting in the bulk of the ignition source being covered by obstructions.

The HRR is only from your ignition burner. It is only 55 kW; I have only run the model for 60 s, but I don't think it is big enough to set the wood on fire.

I suggest your first step is to correct the mis-match between the OBST dimensions and the cell size.

Dave McGill





 

[dr_jfloyd]

Have you tested your wood definition by itself?  This should be the first step if you are going to try and model pyrolysis.  Look at the thermoplastic example in the examples\pyrolysis folder and set up a similar case.using your properties for wood. 

[Minku]

Dear Dave,

I have carried an experiment using wood crib as fire source in a compartment of size 4m by 4m and 4 m. The room is made of ordinary brick. The door size in 1m by 2 m (height) and located is at the center of the front wall. I want to simulate this experiment with the help of FDS. The variation of HRR w.r. t time is as follows.

HRR (kW)        TIme (s)
0.0                    0.0
25                      100 .0
35                      200
70                     300
100                    400
160                   500  
 250                  600
280                    700
340                     800
250                    1000
150                  1200
like wise

Kindly advice how to enter variable heat release rate in FDS to get temperature and velocity as various locations in the enclosure.

Thank u for your reply i am trying the simulation as u suggested i will let u know if any problem comes.

On Wednesday, December 26, 2012 11:49:44 AM UTC+5:30, Minku wrote:

[Dave McGill]

Hello Minku,

It is easy to create a burner to reproduce a specific HRR. See section 8.4.1. It describes how to create a burner with a fixed HRR. Then consult section 10 which describes how to ramp a HRR up and down. That will allow you to reproduce the HRR you have described.  This is considerably simpler than trying to model the combustion of wood as in your original example.

Dave