Aerodynamics and Design for Ultra-Low Reynolds Number Flight

Chapter 2
The results of these time-accurate computations at higher angles of attack indicate that
much higher lift coefficients may be attainable within the unsteady range of operation.
Although inviting, these operating points could be difficult to exploit in practice. The
increase in lift comes at the cost of a very large increase in drag. Increasing the angle of
attack from four to eight degrees more than doubles the drag, to an average value of over
1000 counts. The average lift to drag ratio is roughly maintained, and may even increase
slightly, but the practical issue of providing sufficient power to overcome the drag rise,
combined with the time variation of section performance, complicates the utilization of
these unsteady operating points.
Under the described limitations, INS2d has proven to be a suitable tool for initial
exploration of the ultra-low Reynolds number regime. All reasonable efforts have been
made to validate the accuracy of the code and reduce the possible mechanisms of error,
but a true validation of the code is difficult due to the dearth of relevant experimental and
computational data in the literature. In many ways the data compiled here is the
baseline.
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