PSI - Issue 8

F. Cianetti et al. / Procedia Structural Integrity 8 (2018) 56–66 Author name / Structural IntegrityProcedia 00 (2017) 000 – 000 The modal shape expressed by the polynomium must be characterized by the fact that the independent variable is 1 at the free end (that is the independent variable must be normalized with respect to the length of the tower L ) and that at the free end the value of the modal shape is also equal to 1, that is, the polynomium can be written according to the normalized abscissa: ∅ 1 ( ) = 2 2 + 3 3 + 4 4 + 5 5 + 6 6 (9) with the following condition: ∅ 1 ( ) | =1 = 1 (10) It is obvious therefore that the sumof the coefficients must be equal to the unit: 2 + 3 + 4 + 5 + 6 = 1 (11) From what is said the introduction of flexib ility in the FAST model is reduced to the determination of the five coefficients of the polynomium approximating the modal shape. 61 6

Table 1. Test case wind turbine characteristics (see also fig.4)

WindTurbine Parameters

Values

Unit s

Maximum Power Cut in Wind speed Cut off Wind speed

2800

W

3.0

m/s m/s

15.0

Blades number

3

no unit s

Lp Ht Hv

1.0

m m m m m m

0.98 0.55 0.95 0.13 0.20

Hacc

XG YG

Fig. 4. Representat ion of the test case wind turbine and of it s geomet rical scheme

3. Test case description

In order to evaluate the goodness of the code, especially in non -classical condit ions (i.e . wind tunnel simu lation),