[siw]

I've read various posts about transient time steps etc. and that good practice is to use adaptive timestepping and let CFX find the time step it needs, with 3 to 5 coefficient loops per time step. But it is not clear in these where the values are entered. I have no idea of a constant timestep for my work so adaptive timestepping is the obvious best way ahead.

There are two locations for coefficient loops to be input. In Solver Control, the Convergence Control has Min. Coeff. Loops (1 is default) and Max. Coeff. Loops (10 is default). I assume it is here that the defaults are over-written with 3 and 5, as recommended in other discussions.

However, in the Analysis Setting for the adaptive timestepping values: Total Time, Initial Timestep etc. There are unpopulated boxes for Target Max. Loops. and Target Min. Loops. If 5 and 3 are in here also, CFX complains and the only recourse is a value of 4 for Target Max. and Min. Loops each (unless defaults 1 and 10 are kept in Solution Control).

Hope someone can clarify for me. Thanks

[ghorrocks]

In general the recommended settings are a max of 10 and min of 1 in the max/min coeff loops in the solver settings, and a target max and min of 5 and 3 in the adaptive timestepping target time steps.

I am puzzled by your comment that CFX does not accept target max and min loops of 5 and 3. Something has gone wrong there.

[siw]

Thanks Glenn for clarifying. That is how I set it up.

My description was not clear enough. Anyhow, your first sentence should be flagged at the top of the CFX board. Confirming the assignment of the values to the correct locations which is the important part for me and others who read this.

[evcelica]

CFX did not accept target max and min of 5 and 3 because they also wrote these same values to the max/min coeff loops in the solver settings.
The solver settings must have a lower min and higher max than the adaptive timestep target steps, otherwise no timestep change could take place.