Spread_rate and VENT control logic

[Fredrik (Wuz)]

Hi everyone

I am running a case where I want to ramp the fire with the
'spread_rate' function instead of TAU_Q or the ordinary ramp function.
I am also interesting in starting the fire at a certain time using the
control functions available in FDS 5. I have used two different
control function, none of the worked:

&RAMP ID='CTRL_F1_RAMP', T=84.75, F=-1.00/
&RAMP ID='CTRL_F1_RAMP', T=85.25, F=1.00/

&CTRL ID='CTRL_F1', FUNCTION_TYPE='CUSTOM', RAMP_ID='CTRL_F1_RAMP',
LATCH=.FALSE., INPUT_ID='TIME'/

&VENT XB=62.80,64.00,36.40,37.40,1.00,1.00, SURF_ID='FIRE',
XYZ=63.4,36.40,1.0, CTRL_ID='CTRL_F1', SPREAD_RATE=0.01053 / Fire 1

The output shows that VENT activates at time=85 s and uses the default
ramp up time of 1 s before the hole vent is fully involved in the
fire. The FDS behaviour is the same with my other attempt to activate
the vent:

&VENT XB=62.80,64.00,36.40,37.40,1.00,1.00, SURF_ID='FIRE',
XYZ=63.4,36.40,1.0, DEVC_ID='timer_F1', SPREAD_RATE=0.00471 / Fire 1

&DEVC ID='timer_F1', XYZ=0.00,0.00,0.00, QUANTITY='TIME',
SETPOINT=85.00, INITIAL_STATE=.FALSE. /

Do anyone out have any clue on how to activate a vent at a certain
time and the get the 'spread_rate'-function to control the fire
growth?

Regards
Fredrik

[Chris]

To activate a vent you do it like in the activate_vent-example-case:

&SURF ID='BLOW1', VEL=xxx/
&VENT XB=x1,x2,y1,y2,z1,z1, SURF_ID='BLOW', DEVC_ID='timer 1'/ or with
CTRL_ID='controller 1'/
&DEVC XYZ=x,y,z, ID='timer 1', QUANTITY='TIME', SETPOINT=5.0/

or you make a ramp directly at the SURF-Line which also works.
Cheers
Chris

[Fredrik (Wuz)]

Chris,

Thanks for your advice. Activating a vent is however not my problem.
My issue is that the 'spread_rate' function does not work with the
control logic that I have been using. My VENT is activated, but the
spread_rate command is ignored.

So again:

Do anyone have a clue on how to activate a vent at a certain time and

the get the 'spread_rate'-function to control the fire growth?

Regards
Fredrik

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[Bryan Klein]

Please create a short FDS input file that reproduces your problem and
attach it to a new Issue on the Tracker:
http://code.google.com/p/fds-smv/issues/list

For more information on support options and submission procedures, please see:
http://fire.nist.gov/fds/support.html

Regards,
Bryan Klein

--
Bryan Klein
bryan...@nist.gov

National Institute of Standards and Technology
100 Bureau Drive, Mail Stop 8663
Gaithersburg MD 20899
Phone: 301 975 5171
Fax: 301 975 4052

[Forest]

Hello!

&RAMP ID='CTRL_F1_RAMP', T=84.75, F=-1.00/

Here ,F indicates the fraction of the HRR, wall
temperature,velocity,mass fraction,etc. so F >0 , NOT F=-1.00 <0.

In guide pp 60 , it is indicated that be sure that the prescribed
function starts at T=0.0.
I think that you may add a line as below:
&RAMP ID='CTRL_F1_RAMP', T=0.0, F=0.0/

Please have a try.

Forest


..

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[Fredrik (Wuz)]

The issue has been reported through the issue tracker.
Thanks
/Fredrik

On 17 Dec, 13:22, "Bryan Klein" <bryanwkl...@gmail.com> wrote:
> Please create a short FDS input file that reproduces your problem and
> attach it to a new Issue on the Tracker:http://code.google.com/p/fds-smv/issues/list
>
> For more information on support options and submission procedures, please see:http://fire.nist.gov/fds/support.html
>
> Regards,
> Bryan Klein
>

> bryan.kl...@nist.gov

>
> National Institute of Standards and Technology
> 100 Bureau Drive, Mail Stop 8663
> Gaithersburg MD 20899
> Phone: 301 975 5171

> Fax: 301 975 4052- Dölj citerad text -
>
> - Visa citerad text -