Hello fellow researchers,

I am new here and exploring the structural dynamics of wind turbines for my master’s thesis. (I do not have structural background though).

Right now I have developed a Matlab code to find out the natural frequencies of the whole rotor from scratch and I aim to develop the same routine for openFOAM based simulation(High fidelity, inclding gyroscopic damping, gravitational and rotational stiffness.

So I am stuck at finding the regressive, collective and progressive frequencies (for flapwise, edgewise). I have developed a mass and stiffness matrix but I only get one frequency for all modes (e.g. 1 for 1st flap, 1 for 1st edge, 1 for 1st span, 1 for 2nd flap, and so on…) when I simply find eigenfrequencies using those matrices.

How to find the regressive, progressive and collective frequencies of rotor? I am not even sure if the frequencies I have are of what type of all three above. Would be helpful if I get the theory behind that.

Thanks!