of attack for several Reynolds numbers is calculated by
XFoil [13] and is plotted in Fig. 3. It can be observed that
the minimum pressure coefficient remains high over the
hydrofoil attached flow region. The baseline chord and
pretwist distribution are shown in Fig. 4.a. The rotor speed
(rpm) and pitch angle are plotted in Fig. 4.b.
The comparison between the power and flapwise root
bending moment published data [5], and TTHydro
predictions are shown in Fig. 5. As observed in this figure,
the results obtained with TTHydro agree with data reported
in the literature.
Employing the provided model for normalised induced
twist, β*, given in [11], the normalised flapwise root
bending moment and the normalised induced twist
distribution are found as shown in Fig. 6. The normalised
induced twist represents the distribution of twist induced by
the blade bending. Moreover, the bend-twist experienced by
the tidal turbine blades in operating conditions is shown in
Fig 7. In this example, the tip induced twist (βT,ref) is defined
equal to 5° (toward stall) at the rated flow speed of 2m/s. It
can be seen that the induced twist progressively increases
until the rated operating condition is reached and the
maximum bending moment occurs. Afterwards, the pitch
control reduces the bending moment which consequently
lowers the induced twist.