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