An Accurate Estimation of the Eigenfrequency of an Offshore Wind Turbine Considered as the Stepped Euler-Bernoulli Beam in Three-Spring Flexible Foundation Using the Power Series Method

Table 3

Natural frequencies and comparisons.

OWT name	Natural frequency (Hz) and error (%)
	Measured frequency	Case 1		Case 2		Case 3
		Frequency	Error	Frequency	Error	Frequency	Error
I Lely A2	0.634	0.738	16.53	0.676	6.56	0.727	15.34
II Irene Vorrink	0.546	0.629	15.31	0.562	2.87	0.603	10.51
III Blyth	0.488	0.456	−6.61	0.395	−19.03	0.470	−3.60
IV Kentish flats	0.339	0.348	2.60	0.313	−7.75	0.339	0.01
V Barrow	0.369	0.360	−2.41	0.300	−18.56	0.361	−2.08
VI Thanet	0.370	0.346	−6.57	0.281	−23.97	0.351	−5.19
VII Belwind	0.372	0.378	1.61	0.322	−13.49	0.378	1.34
VIII Burbo Bank	0.292	0.295	0.96	0.2704	−7.39	0.292	0.07
IX Walney	0.350	0.329	−6.08	0.285	−18.54	0.330	−5.68
X Gunfleet Sands	0.314	0.300	−4.42	0.268	−14.52	0.302	−3.82
XI ZJU-P	0.262	0.250	−4.35	0.201	−23.20	0.266	1.45