Blade mass imbalance

Hi Everyone.

My wind turbine model in FAST has 3 blades. I changed the ‘AdjBlMs’ of blade 1 to 1.01 for setting blade mass imbalance, and saw it clearly affect the tower base moment PSD 1P at across wind direction.

However, I want to change more on 1P and set ‘AdjBlMs’ of blade 2 the same value of 1.01 as well, while kept ‘AdjBlMs’ of blade 3 still as 1. The result of 1P shows the same with my first trying (only set imbalance on 1 blade ), that is out of my expectation.

So I wonder how FAST consider the imbalance? Why change on 1 blade and on 2 blades have the same results?

Thanks in advance.
Shuai Wang

Dear Shuai Wang,

I’m not sure what you mean when you say, “[t]he result of 1P shows the same with my first trying”. However, your understanding of how to define a rotor-mass imbalance in the ElastoDyn module of FAST is correct. To increase the imbalance, you could further change the mass of one blade; it is also common to make one blade heavier and one blade lighter than the reference blade when setting the mass imbalance.

Best regards,