I have been using the “NREL offshore 5-MW baseline wind turbine” model. I want to exert an external force on nacelle which is acted on the nacelle mass center with the direction along xn/yn axis. Could you tell me how to exert this force?
I’m assuming you are referring to FAST v7.
There is no direct way of applying this force through a setting in the input file; instead, you’ll have to change the source code. I suggest that you study how the tail-fin aerodynamic loads (internal variables TFinKFx, TFinKFy, and TFinKMz for the forces along the x and y axes and moment about the z axis of the tail-fin coordinate system) are applied to the tail within subroutine FAST.f90/RtHS() and develop similar logic for a load applied to the nacelle.