Aerodynamics and Design for Ultra-Low Reynolds Number Flight

Chapter 6
Prandtl tip loss model and the average wake deficit viscous swirl model. Both of these
designs experience chord Reynolds numbers ranging from 1,000 to 9,000.
The final design is a much larger 5 inch radius two-blade rotor developed for a large
scale flight test model. The Reynolds numbers seen by this rotor are higher than the two
micro-rotor designs, ranging from 8,000 to 25,000. This rotor is a re-design, taking the
chord distribution of an existing commercial product, applying a different airfoil, and
optimizing the incidence distribution. The same version of the code used for the four-
blade rotor is used in this case. It is provided a reference point for the analysis method at
a larger physical scale, where the confidence in the tested rotor geometry is higher,
rotational speed lower, and the measured forces much larger, reducing any measurement
error.
These rotors and others have been designed at various points during the evolution of the
rotor code of Chapter 4. These three cases do not represent all of the designs
manufactured and tested, but provide an experimental reference by which others can be
evaluated. Further iterations and analysis of these designs and others would be desirable,
but the constraints imposed by the rapid pace and structure of the overall mesicopter
development program limited the ability to complete detailed in-depth development of
any single design.
6.2 Motor Selection and Characterization
6.2.1 Myonic 5mm Smoovy Motor
The 2.5cm and 2.2cm diameter rotors have been designed in conjunction with a 15 gram
prototype vehicle to be described in Chapter 7. The motor selected for this application is
the 5mm Smoovy bi-directional brushless DC motor, Model #59002, manufactured by
Myonic Inc. (formerly RMB Inc.) [38]. The motor has a total mass of 1.4 grams and is
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