Candle flame

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Gan

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Oct 8, 2008, 10:05:49 AM10/8/08
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Hi ,
I am actually trying to write an input file for a candle flame in a
room. I have written an input, but I am getting some errors in it
like Poisson initialisation error and coarse pressure computation. I
am including the input file with this mail. I have considered the
candle wax to be a rectangle instead of a cylinder. It will be very
helpful, If you could please help me get the coding straight. Thank
you for spending your time in this matter.

&HEAD CHID='real candle',TITLE='candle flame in a room'/
&MESH IJK=8,8,8,XB = 0.0,40.0,0.0,100.0,0.0,80.0/mesh 1 away from
candle
&MESH IJK=4,4,8,XB = 40.0,60.0,0.0,100.0,0.0,80.0/mesh 2 near the
candle
&MESH IJK=8,8,8,XB = 60.0,100.0,0.0,100.0,0.0,80.0/mesh 3 away from
candle
&MISC PRESSURE_CORRECTION=.TRUE./
&TIME T_END=10.0/

&MATL ID = 'BRICK'
CONDUCTIVITY = 0.69
SPECIFIC_HEAT = 0.84
DENSITY = 1600.0 /
&MATL ID = 'FIBRE'
CONDUCTIVITY = 0.25
SPECIFIC_HEAT = 2.5/

&MATL ID = 'WAX'
CONDUCTIVITY = 0.25
SPECIFIC_HEAT = 2.5
DENSITY = 930.0/
&SURF ID = 'BRICK WALL'
MATL_ID = 'BRICK'
COLOR = 'RED'
BACKING = 'EXPOSED'
THICKNESS = 5.0 /
&SURF ID = 'CANDLE'
MATL_ID = 'WAX'
COLOR = 'BROWN'
THICKNESS = 20.0 /
&SURF ID = 'WICKCANDLE'
MATL_ID = 'FIBRE'
COLOR = 'BLUE'
THICKNESS = 2.0 /
&OBST XB=0.0, 5.0, 0.0, 100.0, 0.0, 80.0, SURF_ID='BRICK WALL' /wall
on left side
&OBST XB=95.0, 100.0, 0.0, 100.0, 0.0, 80.0, SURF_ID='BRICK WALL' /
wall on right side

&OBST XB=45.0, 55.0, 45.0, 55.0, 0.0, 20.0, SURF_ID='CANDLE' /wax of
candle
&OBST XB=48.0, 52.0, 48.0, 52.0, 20.0, 32.0, SURF_ID='WICKCANDLE' /
wick of candle
&SURF ID='FIRE',HRRPUA=1967.0 /flame of the candle
&OBST
XB=45.0,55.0,45.0,55.0,24.0,32.0,SURF_IDS='FIRE','INERT','INERT' /
&SLCF PBZ= 42.0,QUANTITY='VELOCITY', VECTOR=.TRUE. /
&SLCF PBZ= 42.0,QUANTITY='DENSITY', /
&SLCF PBZ= 42.0,QUANTITY='PRESSURE', /
&SLCF PBZ= 42.0,QUANTITY='TEMPERATURE', /
&SLCF PBX= 50.0,QUANTITY='VELOCITY', VECTOR=.TRUE. /
&SLCF PBX= 50.0,QUANTITY='DENSITY', /
&SLCF PBX= 50.0,QUANTITY='PRESSURE', /
&SLCF PBX= 50.0,QUANTITY='TEMPERATURE', /
&SLCF PBY= 50.0,QUANTITY='VELOCITY', VECTOR=.TRUE. /
&SLCF PBY= 50.0,QUANTITY='DENSITY', /
&SLCF PBY= 50.0,QUANTITY='PRESSURE', /
&SLCF PBY= 50.0,QUANTITY='TEMPERATURE', /
&TAIL/

Yours sincerely,
Gan

dr_jfloyd

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Oct 8, 2008, 10:19:55 AM10/8/08
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Distance units are in meters so you have a candle that is 5 m x 5 m x
20 m.
Try increasing the number of grid cells.

Sivaramakrishnan

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Oct 8, 2008, 11:55:37 AM10/8/08
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Hi,
I increased the number of grid cells.  I wanted to know if other than the meshing, is there any other problem with the program? I tried plotting the temperature in a plane using SLCF command, but it gives me a constant temperature throughout inspite of the candle flame in the middle. Do you know how I can fix it? Thank you for your help.
Gan

dr_jfloyd

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Oct 8, 2008, 12:43:00 PM10/8/08
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Does your grid resoltution and OBST defintion result in having a wall
cell present for the FIRE boundary condition? Do you get a non-zero
HRR in the hrr.csv file?
> > > Gan- Hide quoted text -
>
> - Show quoted text -

Sivaramakrishnan

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Oct 8, 2008, 12:53:32 PM10/8/08
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Hi,
I do get a wall cell with the fire boundary condition.  I think there are no zero in the csv file.  The values in the hrr.csv file are as follows.
s kW kW kW kW kg/s atm
FDS_HRR_Time HRR RAD_LOSS  CONV_LOSS  COND_LOSS  BURN_RATE  ZONE_01
0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 9.99E-01
2.14E+00 0.00E+00 0.00E+00 1.89E-04 1.62E-04 0.00E+00 9.99E-01
4.27E+00 0.00E+00 0.00E+00 1.11E-04 1.11E-04 0.00E+00 9.99E-01
6.41E+00 0.00E+00 0.00E+00 7.77E-05 1.27E-05 0.00E+00 9.99E-01
8.55E+00 0.00E+00 0.00E+00 6.49E-05 -2.10E-04 0.00E+00 9.99E-01
1.07E+01 0.00E+00 0.00E+00 7.13E-05 -2.69E-04 0.00E+00 9.99E-01
1.28E+01 0.00E+00 0.00E+00 6.24E-05 -3.95E-04 0.00E+00 9.99E-01


Thank you for your help.
Gan

dr_jfloyd

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Oct 8, 2008, 1:03:36 PM10/8/08
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Did you examine the HRR as a function of time?

Time (s), HRR (kW)
0 , 0
2.14, 0
....
12.8, 0

You have no HRR and thus no temperature rise. Suggest you simplify
your input file to nothing but the OBST with the fire and see what you
get and then add in the additional OBST.



On Oct 8, 12:53 pm, Sivaramakrishnan <bganesh...@gmail.com> wrote:
> Hi,
> > > - Show quoted text -- Hide quoted text -

charlie.thornton

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Oct 9, 2008, 11:03:53 AM10/9/08
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Gan,

You might want to re-check your meshes. Using the following mesh
lines, I got a reasonable-looking (i.e. it wasn't constant)
temperature slice from your original posted input file.

&MESH ID='Grid', IJK=8,20,16, XB=0.00,40.00,0.00,100.00,0.00,80.00/
&MESH ID='Grid03', IJK=8,20,16,
XB=60.00,100.00,0.00,100.00,0.00,80.00/
&MESH ID='Grid02', IJK=8,40,32, XB=40.00,60.00,0.00,100.00,0.00,80.00/

- Charlie

(bummer that we can't attach images...)

Bryan Klein

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Nov 5, 2008, 3:38:24 PM11/5/08
to FDS and Smokeview Discussions
Actually you can attach images, if you email your reply to the
discussion group and attach the image to the email.
You cannot attach in the web interface though, and that is a bit of a
bummer.

Make sure you are sending the email from the same address that is a
member of the group.

-Bryan

On Oct 9, 10:03 am, "charlie.thornton" <charlie.thorn...@gmail.com>
wrote:
> > > > > temperature throughout inspite of thecandleflame in the middle. Do you
> > > > > know how I can fix it? Thank you for your help.
> > > > > Gan
>
> > > >  > On Wed, Oct 8, 2008 at 10:19 AM, dr_jfloyd <drjfl...@gmail.com> wrote:
>
> > > > > > Distance units are in meters so you have acandlethat is 5 m x 5 m x
> > > > > > 20 m.
> > > > > > Try increasing the number of grid cells.
>
> > > > > > On Oct 8, 10:05 am, Gan <bganesh...@gmail.com> wrote:
> > > > > > > Hi ,
> > > > > > > I am actually trying to write an input file for acandleflame in a
> > > > > > > room.  I have written an input, but I am getting some errors in it
> > > > > > > like Poisson initialisation error and coarse pressure computation.  I
> > > > > > > am including the input file with this mail.  I have considered the
> > > > > > >candlewax to be a rectangle instead of a cylinder.  It will be very
> > > > > > > helpful, If you could please help me get the coding straight. Thank
> > > > > > > you for spending your time in this matter.
>
> > > > > > > &HEAD CHID='realcandle',TITLE='candleflame in a room'/
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