Hi @hmattoo, yes that run was much better. I wouldn’t say it diverged but certainly didn’t converge, for this, you need to scrutinise the log more than the convergence plot here is a few snippets:

Time = 0.286886368375

PIMPLE: iteration 1

DILUPBiCG: Solving for Ux, Initial residual = 6.74117971501e-06, Final residual = 6.74117971501e-06, No Iterations 0

DILUPBiCG: Solving for Uy, Initial residual = 1.75298190874e-05, Final residual = 7.93333693667e-08, No Iterations 1

DILUPBiCG: Solving for Uz, Initial residual = 6.26020051249e-06, Final residual = 6.26020051249e-06, No Iterations 0

*GAMG: Solving for p, Initial residual = 0.389706167708, Final residual = 0.000352334314097, No Iterations 5*

time step continuity errors : sum local = 4.20726605867e-11, global = -2.16534466255e-14, cumulative = 2.08006533724e-09

PIMPLE: iteration 2

DILUPBiCG: Solving for Ux, Initial residual = 3.37594193009e-06, Final residual = 3.37594193009e-06, No Iterations 0

DILUPBiCG: Solving for Uy, Initial residual = 9.94923733837e-06, Final residual = 9.94923733837e-06, No Iterations 0

DILUPBiCG: Solving for Uz, Initial residual = 4.12905237522e-06, Final residual = 4.12905237522e-06, No Iterations 0

*DICPCG: Solving for p, Initial residual = 0.158912061823, Final residual = 0.00152583737678, No Iterations 9*

time step continuity errors : sum local = 1.91809715287e-10, global = 8.38393525006e-13, cumulative = 2.08090373077e-09

*PIMPLE: not converged within 2 iterations*

ExecutionTime = 4293.83 s ClockTime = 4765 s

Courant Number mean: 0.00985675328817 max: 0.199950292921

deltaT = 6.07334373398e-05

I’ve bold italicised the bits that are important, the pressure didn’t fall below the termination criteria in 2 iterations. I have found that with 2 correctors I rarely get convergence, I set it to 20 and let it end early if it converges, I find this usually happens in less than 5 outer iterations. This setting is dictated in the ‘Numerics’ section under the number of outer correctors.

As for the Courant number, unless you know the cell sizes its very hard to calculate, your choice to go with auto time stepping is good.

Kind regards,

Darren