In 1972, S. J. Miley30 received his Ph. D. from Mississippi State University with a thesis titled “Analysis of the Design of Airfoil Sections for Low Reynolds Numbers.” His thesis culminated with an example airfoil, the M06-13-128, designed for Rn’s greater than 600k. As the title may suggest, there has been no consensus as to how the term low Rn’s should be defined. A simple way would be to state a cut-off Reynolds number number below which everything is considered low Rn’s. But low Rn’s usually implies laminar separation and high drag. Thus another definition is Rn’s where laminar separation is significant. However, with this definition the Rn would be different for each airfoil. As with any definition, there is some degree of ambiguity, and it may simply be best to state first what Rn’s are being considered, and second, whether or not laminar separation is included in the particular problem under study. In Miley’s case, laminar and turbulent separation were assumed negligible and were ignored in the anaylsis.
• M06-13-128-PT (Fig. 12.56)
As shown in Fig. 12.56, the MILEY airfoil was tested below its design Rn of 600k. At all Rn’s the MILEY airfoil has a high-drag laminar separation bubble as indicated by the large bulge in the polar. In fact for a Rn of 200k, the drag between the stall limits was the highest of any airfoil tested. Consequently we do not recommend it for model sailplanes.
• M06-13-128-PT u. s. bumps xjc = 31%, type A (Fig. 12.57)
• M06-13-128-PT u. s. trips, xjc = 31%, Rn = 200,000 (Fig. 12.58)
(А-trip) h/c = .ll%,wjc = .52%
(В-trip) hjc = .08%,wjc = .52%
(C-trip) zig-zag tape, type В (D-trip) bumps
An upper-surface trip on the MILEY airfoil at 31% produces a dramatic drag reduction—up to 73% at Rn = 200k. For all the cases shown, the А-trip works the best, with the zig-zag tape (C-trip) being next. The В-trip is apparently not high enough (half that of А-trip), as the drag is slightly greater. As for the bumps (D-trip), they do not work as well as the others at high lift, although elsewhere they are as effective as the A – and В-trips. The exact mechanism of these performance differences and how it relates to the shape of the trip is still not well understood.
Also see: SD7003, FX63-137, SD7062 Digitizer plot: Fig. 10.21 Polar plot: Figs. 12.56-12.58 Lift plot: Fig. 12.59
Thickness: 12.81% Camber: 5.16%