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Author Topic: NUMERICAL INSTABILITY  (Read 3092 times)

Senid

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NUMERICAL INSTABILITY
« on: June 20, 2014, 06:23:08 am »

Helo,

a have problem (numerical instability)with this model. How can I solve

thanks
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Dave McGill

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Re: NUMERICAL INSTABILITY
« Reply #1 on: June 20, 2014, 10:31:41 am »

Hi Senid,

Something is very odd. The HRRmax should be 1667 kW/m^2 x 6 m^2 = 10 MW. However, the reported HRR is 400 MW at the time of the numerical instability.

I don't see any obvious reason why, but that is the place to start.

See the attached file. I turned off everything but the burner and it runs with a HRR fluctuating around 11 MW. Something that i have disabled is causing the exaggerated HRR. Add things back in one  at a time.

Dave
« Last Edit: June 20, 2014, 11:01:39 am by Dave McGill »
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Dave McGill
firemodel.ca

Lishi

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Re: NUMERICAL INSTABILITY
« Reply #2 on: June 22, 2014, 10:10:53 pm »


Hello,

Maybe you can change the numerical method from LES to DNS.

Good luck  :)!

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Senid

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Re: NUMERICAL INSTABILITY
« Reply #3 on: June 23, 2014, 04:27:03 am »

Helo Lishi and Dave

when I use DNS for numerical method, simulation (numerical instabillity start) stop at 35,92 s. HRR picture is attached. I dont have new verzion of software Dave and i cannot open your rev. example. Can you save rev. example in PyroSim 2014.1.0110. Thanks you in advance. Stay we in contact.
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Dave McGill

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Re: NUMERICAL INSTABILITY
« Reply #4 on: June 23, 2014, 07:03:04 am »

I can't save to an earlier version of PyroSim. I've attached the .fds file. You can accomplish the same thing with your version of PyroSim by disabling everything but the fire, the obstructions and the open vents.

Dave
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Dave McGill
firemodel.ca