numerical instability error

[kale]

Hello , 

I modelled a  tunnel  and set the simulation time as 200s. while it was in process it stopped suddenly and gave a numerical instability error .

I checked all details and they seemed ok. But,  I suspect to be used inappropriate fire parameters.Therefore, In the first model I had set t^2 fire that ramps up in 1 s. It was wrong and system gave numerically instability error. After that, I set the  t^2 fire and used ram  up time as 30 ,38, 10, 100 for different solutions and even I tried to use default value of the ramp up time option.  However, numerical instability error was given again.

My fire source is a circular porous burner with 0.1 m diameter and 16.7 kW size . So I calculated HRRPUA=2126 kW/m2 . 

I attach some data about this model whose ramp up time 38s.. Could you please help me to understand whether there is any problem of determining of the HRRPUA value and ramp up time or not. And What caused that error?

Thank you so much.

[Anass]

Hi kyle,

Could you attach the fds file because if we don't have pyrosim we cannot open your file?

Regards,

Anass

[MERVE ALTAY]

Here is the FDS file of the model Anass.

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[Randy McDermott]

First, thank you for working with the latest code!  If there are hidden issues this is the only way we can find them.

If this case was working in a version prior to v6.4, it is possible that our increase of the default VN number (in an attempt to speed up the code) is at fault (but no guarantee).  Try setting VN_MAX=0.5 and VN_MIN=0.4 on MISC.  This change is discussed in the release notes:

https://github.com/firemodels/fds-smv/wiki/FDS-Release-Notes

Option B is to tighten your velocity tolerance at a mesh boundary.  See the user guide.

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[MERVE ALTAY]

Thank you McDermott. I have been  trying to find the problem for a week. But i have just noticed my fault. My simulation works smoothly now.

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[MERVE ALTAY]

Mr. McDemort,

Everything was okay but analysis suddenly stopped at 45.simulation time. My ramp up time was 38. s. I set the model changing the VN number as you recommended. I hope it will fix this time.

[MERVE ALTAY]

Mr. McDemort,

Everything was okay but analysis suddenly stopped at 45.simulation time. My ramp up time was 38. s. I set the model changing the VN number as you recommended. I hope it will fix this time.

2016-04-15 13:20 GMT+03:00 Randy McDermott <randy.m...@gmail.com>:

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