Aerodynamics and Design for Ultra-Low Reynolds Number Flight

t/c
0.5
0.4
0.3
0.2
0.1
0.0
FIGURE 6.5 Thickness distributions for the five-blade 2.2cm diameter rotor.
6.3.2 Four-Blade 2.5cm Diameter Rotor
Baseline Incidence
Incidence +3
0.0 0.2 0.4 0.6 0.8 1.0
r/R
Chapter 6
The four-blade 2.5cm diameter rotor was designed using the method of Chapter 4 and
incorporates the wake-deficit viscous swirl model and the Prandtl tip-loss correction.
The goal was to design the smallest rotor capable of generating 4g of thrust using the
5mm Smoovy motor and this resulted in a design operating point of 47,000 RPM. Two
versions have been produced and are pictured in Figure 6.6. The first has a hub diameter
of 2mm, which was later increased to 5mm to improve the torsional stiffness of the
blades. The rotor diameter and blade count are based on a parametric study completed
with the same code. In this case a four-blade design prevailed. The reduction in blade
count from the 2.2cm diameter rotor can be largely attributed to the change in viscous
swirl models. The average wake deficit model will be shown later to discourage high
local solidity, particularly at the inboard stations. This rotor is the last micro-rotor design
to be manufactured during the mesicopter program. The subsequent 3-D CFD analyses,
which provide additional insight into the relevant flow physics and certain trouble spots
101