Blade Element Calculations - Small Wind Turbines: Analysis, Design, and Application - page 99

8. Visit the UIUC web site (URL given in Sect. 4.6 ) and download the lift and
drag data for one of the SG6040, SG6041, or SG6043. Modify the programs
used in this chapter to read in the new data and determine the effect on
performance of changing the aerofoil section. Do not change the blade twist
and chord from that given by tcdist.m .
9. Using tcdist.m to vary the pitch, and then run power-calc.m with the SD7062
lift and drag, estimate the maximum possible C P and compare with the C P from
the optimal twist and chord distributions given by Eqs. 5.12 and 5.13 .
10. For the chord distribution of Eq. 5.12a , show that the Reynolds number, Re,is
approximately constant along a blade operating optimally at a high tip speed
ratio.
11. For the Joukowski model of the blades and wake, explain why only the helical
tip vortices induce flow through the blades.

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