Oscillating Solution e Residuals

Mik511 · February 6, 2019, 12:40

Hi all!

I'm trying to do a pseudo-transient simulation concerning the aerodynamics of a formula car using the k-w SST model but when solving the mesh the residuals keep oscilating and so does the solution. Does anyone know why this happens and how to solve it?

Thank you!

sbaffini · February 7, 2019, 06:15

Give it some more iterations before getting to conclusions.

Also, pseudo-transient, if intended as per Fluent nomenclature, might not be suited and you might need to use a constant, low, CFL number (at least at the beginning).

Wall functions (if your grid has critical y+ values) and some gradient limiters can be problematic as well.

Finally, it can't be excluded, especially if using 2nd order schemes, that a steady solution can't be achieved at all for your case.

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February 7, 2019, 06:15		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,195 Blog Entries: 29 Rep Power: 39	Give it some more iterations before getting to conclusions. Also, pseudo-transient, if intended as per Fluent nomenclature, might not be suited and you might need to use a constant, low, CFL number (at least at the beginning). Wall functions (if your grid has critical y+ values) and some gradient limiters can be problematic as well. Finally, it can't be excluded, especially if using 2nd order schemes, that a steady solution can't be achieved at all for your case.