bugfix: min_steady_timesteps in lbpm_color_simulator

[jeremyfirst22]

Bugfix

• The min_steady_timesteps database parameter was never used to exit upon converged Ca, since Ca_previous was never updated, causing ((fabs((Ca - Ca_previous) / Ca) < tolerance) to always be false. Added a break to exit once the steady point is achieved to avoid continuing to write steady point information until the EXIT_TIMESTEP is achieved.

[JamesEMcClure]

why add analysis_interval here? The previous logic is simply comparing the relative change in the capillary number. This change will alter the interpretation of tolerance

[jeremyfirst22]

@JamesEMcClure I added the analysis_interval here to make the tolerance relative to each simulation step, and independent of the number of steps between evaluating the capillary number.

i.e., if the simulation is not changing by greater than 1% per step, we consider the simulation converged. Not if the simulation is changing by 1% per analysis interval.

The idea was that you should be free to change the analysis_interval without having to adjust the tolerance in kind to achieve the same results.

I agree this changes the interpretation of tolerance, but since the Ca_previous was never updated anyway (i.e., tolerance was never used), I figured I was free to update the interpretation. But 1% per step is an extremely loose default. If you'd like, I will update the default to be consistent with the previous interpretation (1% / 1000 steps)

[jeremyfirst22]

@JamesEMcClure I went ahead and make this change, and updated the default tolerance to 1e-5 so that is consistent with the old interpretation of the default (i..e, 0.01 over the default 1000 steps).

Let me know if you have any other comments on this one.