For internal flow of a gas or liquid through a pipe plus valve, I've been advised that the default Laminar and Turbulent is the best selection, even if the flow is almost, or even at, that a straight pipe.
Conditions are not extreme - normal temp and pressures below 500 psig.
e.g. a simple full-bore ball valve which when fully open will be the same as the pipe internal diameter, although not so if partly closed (like the demo) - has been advised as best usnig the default in either scenario, not just the obvious part-open.
From a Sep 09 post (David P and Joe-G), this seems to be the case - that SW will automatically account for turbulence with that setting, and a setting within that to determine the level when it kicks in.
I haven't quite gotten to renyold's number but I would have thought that if the above is correct, I won't have to as SW will work it?