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Author Topic: Simulation errors!!!  (Read 1404 times)

kale

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Simulation errors!!!
« on: April 19, 2016, 05:21:29 am »

Hi,
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 asked lots of people and run the simulation test cases again and again changing the different parameters of the model but nothing worked and gave the same numerical instability error again. I think the problem is engaged with the time step parameters.
So, In the last simulation study i readjusted CFL number and initial time step. But this time my model gave a different error again . All the datum was attached below, Please help me to find what i should do?

Note: I know the time step size is automatically determined by the CFL condition. So there is no need to type a initial time step . Since i didn't find a solution, I wanted to try that way.

https://www.dropbox.com/s/lcf5cllpib0oqty/time.step.numerical_study_of_effect_of_b.rar?dl=0,

https://www.dropbox.com/s/zmxcfeubpbvv4b4/error.time.step.numerical.study%20of%20effect.log?dl=0


Best Regard
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dar123

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Re: Simulation errors!!!
« Reply #1 on: April 20, 2016, 03:20:21 am »



I've had simulation errors sometimes in points where velocity is very high.

I guess you have jet fans in the tunnel, you can check the velocity vectors to see if there are big velocities that lead to numerical instability. I never touch the time step.

One problem is sometimes that we put a jet fan very near a mesh join and it must be more difficult to the program to make the calculation. The same with the fire source, if is near a "mesh  change".

Well, I hope it is useful for you.

Guillem.
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dar123

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Re: Simulation errors!!!
« Reply #2 on: April 20, 2016, 03:22:53 am »


You can also take a look to the .out file.

In the every step calculation, it gives you where is the max CFL error or something like that, it gives you an advise to see where's the problem.

Regards.
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