Hi,

I am modeling flow in a microchannel and is experiencing convergence issue with the continuity equation. I tried using a lower under-relaxation factor for the momentum and this does help sometimes but not always. Is there anything that I could do to aid/assist the convergence?

Thanks in advance.

Hi. I meet the same problem with yours before. I regenerate grid from Gambit to solve the problem. By the way, I find that sometimes increases some under-relaxation factors can improve the convergence. I want also to get some advice about this problem.

Check mass flux in "report flux" to see whether it is convergent or not

Yes, the mass flux is convergent. I switched to SIMPLEC for the pressure-velocity coupling and used a higher (0.7) under-relaxation factor for pressure and a lower value (0.3) for momentum. Seems to work out pretty well initially. But when I switched to a finer mesh, all the residuals start being unstable (oscillate). Any advice will be appreciated.

Thanks.

Advice: 1 the mesh quality 2 the discretization scheme 3 try to use the coupled solver 4 contact FLUENT for help Good luck

Agree with John

1) Continuity problems normally come from bad meshing - e.g. adjacent cells spacing differs a lot 2) Check your pressure contour plots to see if there are any sharp discontinuities in the lines 3) Run double point precision

Not sure if this could causing the continuity problem - I am using non-conformal meshing...

[abhilasht]

Dear Jake, first try using default values. In case you are not getting convergence then go for URF.

[CeesH]

just how do you end up deciding to answer a 13 year old question?