Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
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Chapter 6<br />
in the rotor geometry, occurred later <strong>and</strong> sufficient time was not available to manufacture<br />
<strong>and</strong> test another design iteration.<br />
102<br />
Large Hub Small Hub<br />
FIGURE 6.6 Four-blade 2.5cm diameter rotors, large <strong>and</strong> small hub versions, inch scale.<br />
The airfoil is the 2-D optimized design <strong>for</strong> Re=6000. The maximum lift coefficient from<br />
INS2d calculations at Re=10,000 is 0.62, increasing to 0.66 at Re=6,000. The operating<br />
point lift coefficient <strong>for</strong> this rotor is constrained to 0.5 to provide stall margin <strong>and</strong> to<br />
account <strong>for</strong> uncertainties in the analysis. The design uses 30 spanwise stations, resulting<br />
in a total of 61 design variables (30 chord values, 30 lift coefficients, <strong>and</strong> RPM). Chords<br />
are limited by an upper bound of 80% local solidity, taken as the ratio of the blade chords<br />
to the local circumference at any given spanwise station. Power required is constrained<br />
to equal power available from the 75 second motor per<strong>for</strong>mance curve. The resulting<br />
chord, incidence, <strong>and</strong> thickness distributions are shown in Figures 6.7 <strong>and</strong> 6.8. The mid-<br />
chord line is unswept. Thickness ratio variations near the tip are due to minimum<br />
thickness manufacturing constraints. Variations at the root <strong>for</strong> the large blade hub were<br />
incorporated to further increase the torsional stiffness.
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