Dear Matthew,
The values of BlPitch specified in the ElastoDyn input file are the initial blade-pitch angles used at the start of the simulation. With active blade-pitch control enabled, these really are just initial conditions and the actual blade-pitch angles will change throughout the simulation. But it is often important to specify the initial conditions to their expected mean value for a given mean wind speed to ensure that the overall time-domain solution is reasonable. I can’t tell from your forum post whether the response you are obtaining is expected or not.
You may get high angle of attack warnings at the inner-most nodes of a blade, which are typically not aerodynamically optimally designed. But I would not expect that you’d receive these warnings at most nodes along the blade. Can you confirm what nodes you receiving this error for?
My understanding is that the IEA Wind 15-MW reference turbine can experience high Mach numbers (exceeding 0.3) due to the high tip-speed ratio it is designed for. This was discussed on our forum here: Mach Number exceeds 0.3 for large wind turbines (15MW) - #4 by Garrett.Barter.
Best regards,