As we know vibration is inherent in several machines. When it comes to wind turbines (VAWTs, in particular), there is possibly some sort of useful vibration that can be used for energy generation, and another kind of vibration which is critical and may cause severe issues such as instability and flutter.

And this needs to be considered when we investigate the the structural dynamic of the turbine.

So I'm trying to understand which source of vibrations in wind turbine and how to differentiate between them actually?

Any suggestion is highly appreciated.