I’m doing a simulation of a small wind turbine (tower height is only 1.2 meters) with Fast because I have the experimentally-measured acceleration of the tower top in xt direction and I want to make a comparison.
I noticed that in the experimental data the acceleration signal has the lowest frequency component(it seems like a sine wave +random signal) that is numerically the same as “blade passing frequency” 3P. Than making a comparison between sperimental acceleration and fast-simulated acceleration i noticed that:
-if i use a “TwrShad” index of 0.3 the xt acceleration from Fast is different from the experimental data(I can not even see the low frequency component)
-if i use “TwrShad” index o 1 the Fast acceleration resambles the sperimental because it has the same lowest frequency component(BPF) and amplitude variation!!
Do you think this is reasonable?I think the difference is that ,in some way that I don’t understand , the higher is TwrShad the higher is the effect of aerodynamic forces that grows from the blade passing near the tower…am I wrong?..can you please explain me this better or send me some reference that explains the “link” between the blade passing aerodynamic forces and TwrShad(if they are linked)?
Thank you very much.