Hello,
I am developing a new simulation tool for floating offshore wind turbines (named MOST) in Matlab/Simulink environment. Now I want to compare the results of MOST with FAST and in particular the blade root forces and moments.
I got a problem with the edgewise force and moment (RootFxb and RootMyb). It seems that in FAST only the gravity force and moment is considered, and the aerodynamic torque is excluded. Indeed, in FAST RootMyb seems a sine function centred to zero, and when I try to subtract the aerodynamic moment from “MOST” curve the curves are the same.
What’s your opinion about that? did I miss something?
In the figure, the plots of blade root forces and moments.
Dear Massimo,
I don’t agree with your assessment. The ElastoDyn module of OpenFAST will return reaction loads at the blade root, which include the contributions from applied aerodynamic loads, gravity, and mass/inertia.
I can’t really explain your results. Can you clarify your simulation set up? How do the results look if you disable the structural DOFs? How do the results look if you disable the structural DOFs and set the blade mass to (near) zero?
Best regards,
Dear Jason,
I solved the problem.
the bladeroot forces in FAST is calculated as:
RootMxb = edgewise aerodynamic moment *sin(blade pitch) + flapwise aerodynamic moment *cos(blade pitch).
in such case the root forces are equivalent to my model.
thank you for the support,
best regards