Comparisons of Theoretical Methods for Predicting Airfoil Aerodynamic Characteristics
Final rept. Sep 2007-Jun 2010
AIRFOILS INC PORT MATILDA PA
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A number of airfoils intended for VTOLRotorcraft applications were tested in the Penn State Low-Speed, Low-Turbulence Wind Tunnel, and the results of these tests compared with those predicted using several well-known theoretical methods. The airfoils considered are the E 387 and the S406, S407, S411, S414, and the S415, and the theoretical methods used are the potential-flowintegral boundary-layer methods, PROFIL07 and XFOIL 6.94, the Euler solverintegral boundary-layer method, MSES 3.05, and the Reynolds-averaged Navier-Stokes solver, OVERFLOW 2.1ae. In addition, several cases were considered using the Navier-Stokes solver, FLUENT 12.1.2, which incorporates the Langtry-Menter four-equation turbulence model that has demonstrated some capability of capturing the transition process. While none of the methods considered was consistently the best overall, the drag predictions of the codes incorporating boundary-layer methods generally agreed better with the experimental results than did those of the Navier-Stokes solvers. All of the theoretical methods frequently over-predicted the maximum lift coefficient, although an empirical criterion developed for use with PROFIL yielded reasonably close agreement with the measurements. The Langtry-Menter turbulence model employed in FLUENT 12.1.2 shows promise in being able to model the transition process, including the development of laminar separation bubbles.