Wind tunnel test and analytical prediction are compared for a range of propellers oriented towards small Unmanned Air Vehicles. Thrust coefficient, torque coefficient and blade efficiency are calculated by iteration between blade-element methods, momentum theory and sectional airfoil analysis. The iteration accounts for low Reynolds number effects by building a large aerodynamic lookup table for sectional properties in the appropriate range of Re. The assumption of uniform inflow velocity increment at the actuator disk, vs. a sectionally-varying inflow, is shown to have minimal loss of accuracy for the blade loadings in this study. Agreement in thrust coefficient between analysis and experiment ranges from mediocre to very good. In all cases predictions are very sensitive to accurate rendition of propeller twist and chord distributions, and to correctly capturing Reynolds-number effects, especially for propellers of small diameter, large blade taper ratio and operation at low advance ratio. Such Reynolds number effects are shown to at least partially explain scatter in experimental data in the traditional presentation of thrust coefficient vs. advance ratio. Scaling of the propeller coefficients is also discussed, with an attempt to relate propeller pitch as an additional quantity in the classical expressions for the coefficients.
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