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Time Step decreases after a long time of running, why? |
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#1 |
New Member
Nidal
Join Date: Nov 2018
Posts: 17
Rep Power: 7 ![]() |
Hi,
My time step starts out at ~1e-9 which is acceptable since my model is basically a 2mm block. After many time steps, almost 1500, my time step decreases to ~1e-15. Anyone knows the reason why this might happen? Thanks a lot ![]() |
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#2 |
Senior Member
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 8 ![]() |
Which simulation you are using? What kind of solver?
Please go through the following link. How to give enough info to get help Assuming that you are using a transient solver, check your CFL(courant number), also, the solver settings and quality of the mesh you are using. If something is not ok please fix it |
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#3 |
New Member
Nidal
Join Date: Nov 2018
Posts: 17
Rep Power: 7 ![]() |
I am using rhoPimpleFoam, When I did the simulation using first order divergence schemes it worked just fine. now that I am solving using second order the time step reduces a lot after some time steps. basically my simulation is a pressure difference across porous media. I have a geometry of a porous structure and I am simulating flow across it. Please let me know if you need more info. My courant number is set to a max of 1, even if I increase it to 5 the time step remains ~1e-15
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#4 |
Senior Member
Kmeti Rao
Join Date: May 2019
Posts: 145
Rep Power: 8 ![]() |
I have not carried out simulations in your application but during dynamic simulation of external flow over a propeller, I had similar issues. I have overcome that by improving the quality of mesh and calculating the possible time step using CFL.
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#5 |
Member
Jan Majcher
Join Date: Nov 2018
Posts: 39
Rep Power: 7 ![]() |
Hi Kmeti,
May I ask you how exactly did you improve the mesh quality? Did you decrease non-orthogonality? Cheers, Jan |
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