How to impose continue step increase rotational speed in OpenFAST?

[winder365]

Dear all,

I want to conduct a special simulation with continue step increase rotational speed of rotor in OpenFAST. I have known how to impose step increase wind velocity in OpenFAST (as shown in the figure), is there similar approach for rotational speed?

Thank you for your attention!

[jjonkman]

Dear @winder365,

The short answer is "no".

Generator rotation is a degree of freedom of the ElastoDyn module of OpenFAST. As such, its motion is determined by a balance between the applied torques. If you want step changes in speed, you'd have to set the generator torque such that the speed has the profile you want. That said, you can't directly specify the aerodynamic torque, and it is the difference between generator and aerodynamic torques that will determine the generator acceleration. Also, the generator speed is the integral of the generator acceleration, so, step changes in speed are not possible, but will involve smoother motion than a step function.

Best regards,