Monopile Foundation Stiffness Estimation of an Instrumented Offshore Wind Turbine through Model Updating

Figure 13

Normalised natural frequencies predicted by the PISA model founded flexible rotor finite element model variation with blade stiffness factor α. Coloured lines map the trend of each n^th eigenvalue of the system mass and stiffness matrices and are consistent between subfigures. (a) All modes. (b) 1^st tower dominated modes. (c) 2^nd tower dominated modes. (d) 3^rd tower dominated modes.

(a)

(b)

(c)

(d)