Search found 4105 matches

by Yvan Fournier
Wed Jun 12, 2024 1:16 am
Forum: code_saturne usage
Topic: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations
Replies: 5
Views: 403

Re: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations

Hello, The sensitivity to the time step is a headache for us too, though recurring posts on this forum are quite interesting, as they add important knowledge and insight, and this issue is often forgotten, as it is much more sensitive for some types of computations than for others (for example a use...
by Yvan Fournier
Thu Jun 06, 2024 1:12 am
Forum: code_saturne usage
Topic: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations
Replies: 5
Views: 403

Re: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations

Hello, I mentioned your post to other colleagues who have more expertise in the numerics of the code, and I'll remind them to check, but I know of no option more relevant than adjusting rcfact, using a local time step (pseudo-steady option), or changing the mesh. In you listed options, I do not see ...
by Yvan Fournier
Fri May 31, 2024 12:33 pm
Forum: code_saturne usage
Topic: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations
Replies: 5
Views: 403

Re: Pressure Checkerboard Patterns in Vehicle Aerodynamics Simulations

Hello, What CFL number do you have ? Checkerboarding can appear in areas where the time step is very small relative to the mesh size and velocoty, so that the Rhie&Chow coupling (which is unfortunately sensitive to the time step) becomes less effective. I am not aware of checkerboarding in other...
by Yvan Fournier
Fri May 24, 2024 9:50 pm
Forum: code_saturne usage
Topic: Second-Order Temporal Discretization Except for Turbulence Model Equations
Replies: 6
Views: 707

Re: Second-Order Temporal Discretization Except for Turbulence Model Equations

Hello,

I asked a colleague, who told me trying to force 2nd order this way is risky and might ne behave well, and that a PhD student might be looking into this soon, but have no more details.

I'll keep you updated if I get more info on what can be done.

Best regards,

Yvan
by Yvan Fournier
Fri May 24, 2024 9:47 pm
Forum: code_saturne usage
Topic: Steady-Compressible flow
Replies: 6
Views: 3493

Re: Steady-Compressible flow

Hello, Yes, your setting seems OK. I am not sure the pseudo-steady algorithm matches that on your reference, as I am not familiar with the book. It would be interesting to compare. In our case, the code simply adjusts the time step in each cell so as to try to target a CFL of 1. The reference time s...
by Yvan Fournier
Sun May 19, 2024 2:43 pm
Forum: code_saturne usage
Topic: model validation
Replies: 5
Views: 475

Re: model validation

Hello, If you get different results each time, there may be some memory corruption, which indicates a bug... How large is your test case ? If it is not too big, I would be interested in running it under a tool such as Valgrind or a build using AdressSanitizer to check for a bug in code_saturne... If...
by Yvan Fournier
Sat May 18, 2024 12:33 am
Forum: code_saturne usage
Topic: Second-Order Temporal Discretization Except for Turbulence Model Equations
Replies: 6
Views: 707

Re: Second-Order Temporal Discretization Except for Turbulence Model Equations

Hello,

Any detailed feedback on this is very welcome :-)

Best regards,

Yvan
by Yvan Fournier
Sat May 18, 2024 12:32 am
Forum: code_saturne usage
Topic: Cannot use TVD schemes
Replies: 9
Views: 716

Re: Cannot use TVD schemes

Hello, Yes, I would have been interested in testing this for some cases to improve robustness, but was stuck at this point, and am already too busy with other parts of the code to realistically expect to work on this in the near future. But helping others do it might add a bit of leverage. Best rega...
by Yvan Fournier
Fri May 17, 2024 1:16 pm
Forum: code_saturne usage
Topic: model validation
Replies: 5
Views: 475

Re: model validation

Hello, What do you mean by "calculation gets corrupted" ? - Does the code crash on an invalid memory access error ? - Or are the results bad/unexpected ? If the code runs but provides incorrect results, you may have a mesh quality issue. Notably, if cells inserted in the viscous layer have...
by Yvan Fournier
Fri May 17, 2024 12:57 pm
Forum: code_saturne usage
Topic: Second-Order Temporal Discretization Except for Turbulence Model Equations
Replies: 6
Views: 707

Re: Second-Order Temporal Discretization Except for Turbulence Model Equations

Hello, I know the handling of "per variable" time scheme is a complicated mess, with some options that have been available for years but never really tested, and others which may be missing but would make sense. I am not too well versed in this part of the code, but will ask some colleague...