device activation

[Ricky]

Hello everyone,

I have a strange problem with FDS. In my simulation, certain opening
is opened after 30 minutes with activation of a vent. I just found
that, after a vent is activated, my simulation is stopped although its
runtime is 45 minutes. Here is the main lines of device activation
from my input file:

&HOLE XB=0.20,35.20,0.0,0.20,3.40,5.00,COLOR='BLUE', DEVC_ID='timer 1'/
Light band

&HOLE XB=35.20,35.40,5.40,10.00,0.00,4.60,COLOR='BLUE', DEVC_ID='timer
2'/Door opening

&DEVC XYZ=17.4,0.2,4.2, ID='timer 1', SETPOINT= 1800.,
QUANTITY='TIME', INITIAL_STATE=.FALSE./
&DEVC XYZ=35.4,7.6,2.4, ID='timer 2', SETPOINT= 1800.,
QUANTITY='TIME', INITIAL_STATE=.FALSE./

I am using FDS 5.3.1 serial version. Has anyone experienced the same
problem? Can anyone tell me what is the problem in my case?

Thanks a lot in advance.

Regards,
Ricky

[Kevin]

We just released FDS 5.5.0. Try this newer version. If you have a
problem, submit a simple example input file to the Issue Tracker that
demonstrates the problem. The information that you have provided in
your post is not sufficient to diagnose the problem.

[Ricky]

Thank you Kevin for your reply. Well, for a small problem, I dont have
this issue. Right now I am simulating a fire in a big industrial hall
(35x15x6 m^3). In this case, I have a big window (35 x 1.6 m^2) that
opens at 1800 s. When this happens, I can see a huge increase in CFL
no in the .out file and then the simulation stops. Here is a snippet
from .out file:

Time Step 47700 April 20, 2010 06:31:34
----------------------------------------------
CPU/step: 8.236 s, Total CPU: 110.10 hr
Time step: 0.08980 s, Total time: 1791.37 s
Max CFL number: 0.41E+00 at (102,101, 5)
Max divergence: 0.26E-01 at ( 63, 86, 1)
Min divergence: -0.19E-01 at ( 82, 86, 1)
Max div. error: 0.59E-06 at ( 3,101, 30)
No. of Lagrangian Particles: 499352
Radiation Loss to Boundaries: 53.035 kW

Time Step 47799 April 20, 2010 06:45:15
----------------------------------------------
CPU/step: 8.223 s, Total CPU: 110.33 hr
Time step: 0.00000 s, Total time: 1800.17 s
Max CFL number: 0.25E+06 at ( 2, 26, 25)
Max divergence: 0.83E+07 at ( 16, 25, 25)
Min divergence: -0.46E+07 at ( 17, 25, 25)
Max div. error: 0.60E-06 at ( 3,101, 30)
No. of Lagrangian Particles: 499354
Total Heat Release Rate: 2592.147 kW
Radiation Loss to Boundaries: 964.619 kW



DEVICE Activation Times

1 LB 1 1800.1 s


So, I think its numerical instability problem. Doesnt FDS displays any
error message for such instabilities?

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[Kevin]

Yes, this appears to be a numerical instability, probably related to
the opening of the vent. There is probably an indication of this at
the end of the .out file.

> For more options, visit this group athttp://groups.google.com/group/fds-smv?hl=en.- Hide quoted text -
>
> - Show quoted text -

[Ricky]

No, the .out file doesn't say anything about this. Here is the last
lines from .out file:
Time Step 42888 April 10, 2010 04:55:27
----------------------------------------------
CPU/step: 5.473 s, Total CPU: 56.85 hr
Time step: 0.00000 s, Total time: 1800.12 s
Max CFL number: 0.65E+07 at ( 2, 26, 25)
Max divergence: 0.36E+09 at ( 21, 28, 25)
Min divergence: -0.17E+10 at (176, 75, 13)
Max div. error: 0.29E-05 at (176, 75, 13)
No. of Lagrangian Particles: 499362
Total Heat Release Rate: 46364.564 kW
Radiation Loss to Boundaries: 19234.475 kW



DEVICE Activation Times

1 timer 1 1800.0 s
2 timer 2 1800.0 s


CPU Time Usage, Mesh 1

CPU (s) %
----------------------------
MAIN 204731.56 100.00
DIVG 32148.22 15.70
MASS 59284.40 28.96
VELO 33045.82 16.14
PRES 21270.02 10.39
WALL 7458.84 3.64
DUMP 2570.11 1.26
PART 11888.89 5.81
RADI 32687.92 15.97
FIRE 4323.42 2.11
COMM 0.15 0.00
SubTot 204677.79 99.97


Time Stepping Wall Clock Time (s): 209217.153
Total Elapsed Wall Clock Time (s): 209221.671

That is all the .out file says.But I was thinking if there is a
numerical instability, fds should display an error message.

On Apr 22, 10:44 pm, Kevin <mcgra...@gmail.com> wrote:
> Yes, this appears to be a numerical instability, probably related to

> the opening of thevent. There is probably an indication of this at

> > > > is opened after 30 minutes withactivationof avent. I just found
> > > > that, after aventis activated, my simulation is stopped although its

> > > > runtime is 45 minutes. Here is the main lines ofdeviceactivation
> > > > from my input file:
>
> > > > &HOLE XB=0.20,35.20,0.0,0.20,3.40,5.00,COLOR='BLUE', DEVC_ID='timer 1'/
> > > > Light band
>
> > > > &HOLE XB=35.20,35.40,5.40,10.00,0.00,4.60,COLOR='BLUE', DEVC_ID='timer
> > > > 2'/Door opening
>
> > > > &DEVC XYZ=17.4,0.2,4.2, ID='timer 1', SETPOINT= 1800.,
> > > > QUANTITY='TIME', INITIAL_STATE=.FALSE./
> > > > &DEVC XYZ=35.4,7.6,2.4, ID='timer 2', SETPOINT= 1800.,
> > > > QUANTITY='TIME', INITIAL_STATE=.FALSE./
>
> > > > I am using FDS 5.3.1 serial version. Has anyone experienced the same
> > > > problem? Can anyone tell me what is the problem in my case?
>
> > > > Thanks a lot in advance.
>
> > > > Regards,
> > > > Ricky
>
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[dr_jfloyd]

Time step = 0.00000 s and Max CFL = 10E6. You have a numerical
instability.

> > > For more options, visit this group athttp://groups.google.com/group/fds-smv?hl=en.-Hidequoted text -