Hello Tainá, how are you? I don't know exactly the answer for your problem, but let me tell you something that I've seen when simulating with a passive scalar in Nektar++. The passive scalar should be limited to the values (range) that you impose (you can think about it as temperature), so the values outside the limits are related to numerical error. You would decrease this error with mesh or p refinement, but I don't think that you would do that with SVV at first, as it serves as a stabilization method adding dissipation. So, if you really can have this numerical issue, I suggest that you refine the mesh or increase the number of modes. Sincerely, Daniel. Em ter., 22 de out. de 2024 às 20:47, Tainá Gomes Rodovalho < tainarodovalho@usp.br> escreveu:

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Hello Nectar++ users,

I am analyzing the dispersion of a solute in an incompressible, laminar flow with a low Reynolds number using the IncNavierStokes solver with passive scalar transport.

I've adapted the model from the Backward-facing step <https://doc.nektar.info/tutorials/latest/flow-stability/bfs/flow-stability-bfs.html> tutorial with an additional infusion point in the upper region of the channel, particularly within the step region. However, I've encountered negative concentration values in simulations. To address this, I activated SVV True (second test), although I had a slight reduction in negative concentration regions. I also conducted mesh refinement (third test), which improved the situation but significantly increased computational costs. If possible, I would appreciate any suggestions and, additionally, I would like to know more about SVV.

Thank you in advance.

Best regards,

Tainá Gomes Rodovalho

P.S.: Attached are the concentration images for the tests performed. _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users