2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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due to surface roughness lessened slightly from the 11%
escarpment to the 20% escarpment (Fig. 19b).
Fig. 15. Escarpment with no turbine: effects of roughness on turbulence
intensity for escarpments of (a) 11% and (b) 20%.
Fig. 16. Escarpment with no turbine: effects of roughness on vertical
flow angle for escarpments of (a) 11% and (b) 20%.
The operating rotor (Fig. 20) significantly reduced the
roughness effect on the NTF, and all differences observed
for the non-operating turbine (Fig. 19) were reduced by
nearly half.
C. Hub height effects
The significance of hub height effects on the location
of the nacelle anemometer was analysed by varying the
height of the Jeumont turbine on a flat terrain. By moving
the J48 nacelle from 0.75
D
to 1.25
D
(Fig. 21), the speed
predicted at the anemometer proved to be slightly higher
than what had been predicted by the logarithmic profile;
the slope of the
U
nacelle
/U
∞
curves remained almost
unchanged.
Fig. 17. Non-operating turbine: effects of roughness on axial velocity
and vertical flow angle for escarpments of (a) 11% and (b) 20%.
Fig. 18. Operating turbine: effects of roughness on axial velocity and
vertical flow angle for escarpments of (a) 11% and (b) 20%.
Fig. 19. Non-operating turbine: effects of roughness on NTF for
escarpments of (a) 11% and (b) 20%.
