Add to the docs a better explanation about max_change and min_change of the TimeStepWizard

[iuryt]

Hi,

I have been confused about what the max_change and min_change means.
I understand from the documentation that this is to avoid the time step to change too quickly, but how is it used?

Is it in time units? e.g., taking the default max_change of 1.1, that means that for dated simulation it will change the time step at max in 1.1 seconds?

Is it a multiplication? e.g., new_time_step = 1.1*time_step ?

I think we can try to be more clear about that in the docs.

[glwagner]

It's the latter: max_change is the maximum relative change of the time step and is therefore non-dimensional. Thus the new time step satisfies the criteria

new_dt <= max_change * old_dt

It's implemented here:

Oceananigans.jl/src/Simulations/time_step_wizard.jl

Lines 96 to 99 in 0d39f5c

	# Put the kibosh on if needed
	new_Δt = min(wizard.max_change * old_Δt, new_Δt)
	new_Δt = max(wizard.min_change * old_Δt, new_Δt)
	new_Δt = clamp(new_Δt, wizard.min_Δt, wizard.max_Δt)

Improving the docs is always a good idea!

[iuryt]

I add that to the docs.