Convergence issue with continuity equation
 

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.

Re: Convergence issue with continuity equation
 

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.

Re: Convergence issue with continuity equation
 

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

Re: Convergence issue with continuity equation
 

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.

Re: Convergence issue with continuity equation
 

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

Re: Convergence issue with continuity equation
 

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

Re: Convergence issue with continuity equation
 

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

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

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