Transition at Low-Re Numbers for Uav Type Airfoils at High Subsonic Mach Numbers

Abstract

High altitude long endurance UAV flight regime imposes certain difficult testing conditions for the ground based test facilities, such as low density, low freestream turbulence, high alpha, low-Reynolds, and highsubsonic- Mach numbers. High altitude flight testing would be required to collect actual experimental data at an expense of much higher costs. Computational approach is a viable alternative to support generation of design data base for the laminar and transitional boundary layers at high-subsonic-Mach-numbers. In the present study, a two-equation ?-Re?t correlation-based transition model is further developed to predict some airfoils that are frequently used in the design of UAVs. Firstly, the empirical correlations already validated for low to high Mach number flat plate cases is validated for the thin NACA64A006 airfoil at low subsonic speed and high-Reynolds-number. Secondly, the present methodology is successfully demonstrated for the E387 and SD7037 moderately thick UAV type airfoils in the low-Reynolds and low-subsonic-Mach-number conditions. Finally, the relatively thicker APEX-16 airfoils at high-altitude, low-Reynolds-number conditions for high-subsonic Mach numbers are simulated. Results are compared with the available numerical data in the literature obtained through Reynolds Averaged Navier-Stokes and viscous-inviscid interaction methods using the eN method. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.