Correlation of Theory to Wind-Tunnel Data at Reynolds Numbers below 500,000

Abstract

This paper presents results obtained from two airfoil analysis methods compared with previously published wind tunnel test data at chord Reynolds numbers below 500,000. The analysis methods are from the Eppler-Somers airfoil design/analysis code and from ISES, the Drela-Giles airfoil design/analysis code. The experimental data are from recent tests of the Eppler 387 airfoil in the NASA Langley Low Turbulence Pressure Tunnel. For R ≥ 200,000, lift and pitching moment predictions from both theories compare well with experiment. Drag predictions from both theories also agree with experiment, although to different degrees. The Drela-Giles code also predicts pressure distributions which compare well with the experimental pressure distributions, including those cases with laminar separation bubbles. For Reynolds numbers of 60,000 and 100,000, lift and pitching moment predictions from both theories are in fair agreement with experiment. However, most of the drag predictions from the Eppler-Somers code are accompanied with separation bubble warnings which indicate that the drag predictions are too low. With the Drela-Giles code, there is a large discrepancy between the computed and experimental pressure distributions in cases with laminar separation bubbles, although the drag polar predictions are similar in trend to experiment.