The lab-scale model of the FWT (Fig.1(a)), which is designed in the University<\/p>\n\n\n\n
of Patras and manufactured by the \u201cAlphamach.gr\u201d<\/strong>, consists of the main tower,<\/p>\n\n\n\n the rotor, the blades, a tension leg platform also known as the floater of the<\/p>\n\n\n\n FWT [19], a base plate and three springs. The tower houses the rotor which<\/p>\n\n\n\n is connected to the blades, as well as it is connected at its lower part with<\/p>\n\n\n\n the platform through bolts. The base plate and the three springs are used for<\/p>\n\n\n\n the emulation of the FWTs motion with the constraints from its mounting to<\/p>\n\n\n\n the sea bottom through typical mooring lines. The FWT model rotates normally<\/p>\n\n\n\n under 9 different operating conditions that result from 3 wind speeds, designated<\/p>\n\n\n\n as WS1, WS2 and WS3, and 3 wind directions WD1, WD2 and WD3. These<\/p>\n\n\n\n conditions are achieved by adjusting both the rotating speed and the direction<\/p>\n\n\n\n 4 J.S. Korolis et al.L<\/p>\n\n\n\n m<\/p>\n\n\n\n Meas.<\/p>\n\n\n\n direction<\/p>\n\n\n\n Accelerometer<\/p>\n\n\n\n Blade Crack (BC)<\/p>\n\n\n\n Added Mass (AM)<\/p>\n\n\n\n Connect. Degrad. (CD)<\/p>\n\n\n\n (b)<\/p>\n\n\n\n (c)<\/p>\n\n\n\n (d)<\/p>\n\n\n\n (e) (a)<\/p>\n\n\n\n (f)<\/p>\n\n\n\n Fig. 1. (a) The lab-scale FWT model, (b) accelerometer position, (c) Blade Crack<\/p>\n\n\n\n (BC), (d) Added Mass (AM ), (e) Connection Degradation (CD) and (f) fan location<\/p>\n\n\n\n (wind speeds WS1, WS2, WS3 and directions WD1, WD2, WD3).<\/p>\n\n\n\n of a fan with respect to the FWT model as illustrated in Fig.1(f). Three different<\/p>\n\n\n\n early-stage damages are considered separately on the FWT model including: (i)<\/p>\n\n\n\n Blade Crack (L = 3 cm, 8% of the total blade length) as shown in Fig. 1(c),<\/p>\n\n\n\n designated as \u2018BC\u2019, (ii) Added Mass (m = 2.3 g) on a single blade simulating<\/p>\n\n\n\n potential ice accumulation as shown in Fig. 1(d), designated as \u2018AM \u2019, and (iii)<\/p>\n\n\n\n Connection Degradation between tower and floater implemented by removing<\/p>\n\n\n\n two out of the total eight mounting bolts as shown in Fig. 1(e), designated as<\/p>\n\n\n\n \u2018CD\u2019.<\/p>\n\n\n\n