Two reports concerning the aerodynamics of small Reynolds Number airfoils are presented within the pages of this Web site. The first report, by Richard A. Hyman, NAR 10841, rickhyman@aol.com details the investigation of different types of airfoils used for small gliders with Reynolds numbers in the range of 5,000 to 50,000. These types of gliders are often used as the gliding portion of a type of model rocket called a boost glider.
The second report by Bruce Markielewski, NAR 38377, markielewski@purplemtn.com details the investigation of small airfoils used for the blades of a helicopter type recovery system, another type of model rocket event. The Reynolds number for these blades can be even lower than the small gliders, as low as 2,000.
For more information on model rocket competition and events, go to:
www.NAR.org
In the past, it has been known by aerodynamicists that the results of airfoil research in Reynolds Number ranges as low as 100,000 and sometimes 50,000 cannot be applied with any confidence to lower Reynolds numbers. Due to changes in flow, airfoil characteristics seem to change quickly at Reynolds Numbers below 100,000. The lack of research in low Reynolds Numbers is unfortunate because many small model aircraft operate in these very low ranges, including most gliders flown within the limits of rules used in NAR events. Many competitors have simply assumed that airfoil data published for higher Reynolds Numbers can be consistently used at the lower ranges, and then do not understand why they have failed to reach the level of competition hoped.
Ideally, very small Reynolds number airfoils would be investigated using low speed a low speed wind tunnel with very accurate measuring instruments. We do not have this type of wind tunnel available, and so two different approaches were taken in these investigations. The approaches are not as accurate as one might wish, but we were investigating airfoils that differ in gross ways, so we were expecting more easily discernible results than those of airfoils having minor differences. Therefore, the conclusions expressed in these reports are limited to the simple comparison of widely differing types of airfoils at low Reynolds numbers, and are not concerned with the absolute measurement of lift and drag values of those airfoils.
Both of these reports were presented as entries in the R&D event at the model rocketry national championships, known as NARAM 2000 (www.naram2000.org), in Canon City, Colorado during the week of July 31 through August 4, 2000. The first report was awarded 2nd place and the second report herein was awarded 3rd place.
To view the complete reports online, use one of the following links:
Report 1: Small and Very Small Reynolds Number Airfoils
© copyright 2000 by Richard A. Hyman. All rights reserved.