simulation stops suddenly

[gforney]

Please complete the following lines...

FDS Version: 6.0.0
SVN Revision Number:
Compile Date: may 14 2014
Smokeview Version/Revision: 6.1.5
Operating System: OSX Mavericks

Describe details of the issue below:
Hi,
I'm trying to run a simulation of a pool of DMDS but simulation stops suddenly and
i get this message (see attachment). I would like to know what does it mean and how
could I fix it.
Thanks for your time 
Eduardo Becerra

Original issue reported on code.google.com by matarielz on 2014-05-15 02:16:12

---

• Attachment: Screen Shot 2014-05-14 at 9.39.11 PM.png
  
• Attachment: prueba.fds

[gforney]

You haven't set a heat capacity for (CH3)2S2.  Therefore FDS is trying to compute the
heat capacity using gamma and the molecular weight.  However, the default gamma is
not appropriate for (CH3)2S2 resulting in a heat capacity of 300 kJ.  This isn't causing
your problem.  Fixing that doesn't solve the crash however which is still happening
with the latest source.  Once we find the cause we might be able to suggest a work
around.

Original issue reported on code.google.com by drjfloyd on 2014-05-15 12:20:38

• Labels added: Application-FDS

[gforney]

The issue is your pool surface.  You have only specified a liquid layer.  When the pool
burns out, FDS doesn't know how to treat that boundary any more.   Add a concrete layer
underneath the liquid.  Based on your default wall (note your 'wall' CONCRETE SURF
has THICKNESS=0.0012.  This is 1.2 mm of concrete.  Is that correct?) change this:

&SURF ID  ='pool', 
        RGB       =200,200,200, 
        MATL_ID   ='DMDSliquido'
        THICKNESS =0.0012 /
        a type of boundary conditions named 'pool'

To this:

&SURF ID  ='pool', 
        RGB       =200,200,200, 
        MATL_ID   ='DMDSliquido','CONCRETE'
        THICKNESS =0.0012,0.0012 /
        a type of boundary conditions named 'pool'

and it runs.

Original issue reported on code.google.com by drjfloyd on 2014-05-15 14:50:22

[gforney]

Thank you very much for taking the time to address this issue. I did add as
you mentioned, a solid surface, however I still can't run a complete
 simulation, as it now stops at time step 33 because of a numerical
instability.

I'm sorry for pressing on the matter, but I can't figure out what's wrong.

I hope you can help me again

Original issue reported on code.google.com by matarielz on 2014-05-16 00:56:30

[gforney]

Did you give a reasonable specific heat for the gas on the SPEC line?

If you have done that and still have problems, we will need your current input file.

Original issue reported on code.google.com by drjfloyd on 2014-05-16 00:58:57

[gforney]

Hi, yes, I did give a specific heat to the gas. here's the input file.

Original issue reported on code.google.com by matarielz on 2014-05-19 12:03:15

[gforney]

No file was attached.  The webpage is indicating your last response was via email. 
You may need to use the web interface to successfully attach a file to tracker.

Original issue reported on code.google.com by drjfloyd on 2014-05-19 12:04:52

[gforney]

ok, here's the input file

Original issue reported on code.google.com by matarielz on 2014-05-19 14:00:31

---

• Attachment: prueba.fds
• Attachment: Screen Shot 2014-05-19 at 9.20.55 AM.png
  

[gforney]

Is your thermal conductivity correct?  You have it as 0.0083 W/m-K.  This is about an
order of magnitude less than fiberglass insulation and seems awfully low for a liquid.
 At that value the surface temperature will swing wildly in response to the heat flux
and I think this is causing your instability.  

Original issue reported on code.google.com by drjfloyd on 2014-05-19 15:49:31

[gforney]

You are absolutely right. That's gas phase thermal conductivity, not condensed phase.

Thanks for your help

Original issue reported on code.google.com by matarielz on 2014-05-19 16:53:56

[gforney]

Thanks for letting us know it is now working.

Original issue reported on code.google.com by drjfloyd on 2014-05-20 12:15:14