I’m currently working on the linearization of 10MW OnShore RWT model. The parameters fixed for the linearization are rotor speed equal to 9.6 rpm, blade pitch equal to 9.292° for the three blades and steady wind with speed equal to 14 m/s, while the rotor azimuth angles selected for the linearizations are 0°:22.5°:337.5°(hence 16 angles were considered). The inputs considered are Blade1(B1) individual pitch, B2 individual pitch, B3 individual pitch and collective pitch, while the outputs considered are FlapWise bending moment at B1, B2 and B3 roots.
The model is defined using InflowWind, AeroDyn15, ElastoDyn and BeamDyn, in particular the WT was modelled without BeamDyn first; the purpose was to compare the results obtained by linearization performed on a flexible WT(FlapDOF1 EdgeDOF TwFADOF1 TwSSDOF1 activated) featured by isotropic blades(hence NO Bend-Twist Coupling) modelled by ElastoDyn(CompElast=1) first and then modelled by ElastoDyn+BeamDyn for blades(CompElast=2).
The desired result from the comparison was the coherence between the TFs obtained from linearizations performed on models in which different tools were implied to model same structural characteristics, hence input-output transfer functions obtained by a model defined through ElastoDyn must be quite similar to the ones obtained by a model defined through ElastoDyn+BeamDyn.
The desired results was not reached, in particular problems related to numerical instability(I think) are highlighted using BeamDyn; it turns out that using different OrderElement(I used 4 with time step=0.001s,5 and 6 with time step=0.0005s) number the resulting TFs are different. I attached a folder containing images related to TFs obtained using ElastoDyn only and ElastoDyn+BeamDyn with different OrderElement considering for all the cases rotor azimuth angle equal to 0°(the TFs are considered in a frequency range of [0.12pi rad/s : 2*pi rad/s] since that is my range of interest). I attached a folder which includes the models I used to perform linearization.
I’m asking help to understand the cause of TFs’ variation due to OrderElement changes and I would like to define the reason of the differences between the TFs computed using ElastoDyn only and using ElastoDyn+BeamDyn which are(should be) defining the same structural model.
Thanks in advance.