Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

Unmanned Aerial Vehicles, UAVs, gained an important role in modern military and civilian applications. Developments in UAVs technology improve its performance and maneuverability with acceptable cost. Elliptic airfoil had been widely used in the development of Rotor/Wing subsonic aircraft. The present work aims to investigate the effect of various elliptic airfoil parameters, such as Reynolds number, angle of attack and airfoil thickness, on aerodynamic behavior using two-dimensional computational study. The computational results were validated by experimental results. Angles of attack was evaluated from 0Â° to 18Â° in order to analyze aerodynamic characteristics up to stall condition, while Reynolds number was evaluated at values of 1Ã—10âµ, 3Ã—105, 2Ã—106, and 8Ã—106, to cover the range of rotary and fixed wing flight conditions. Thickness ratio was ranged from 5% to 25% to include the UAVs airfoil thicknesses so that choice best thickness gets max lift to drag ratio. In addition, the thicknesses location was evaluated for a range of 30% to 70% to get suitable location gets max left to drag ratio. The ANSYS-Fluent software was used with Spalart-Allmaras turbulence model, and found that the maximum lift to drag ratio which improve the UAV capability in this study is at Re=2Ã—106, angle of attack at 8Â°, max thickness ratio of (0.1chord) located at (0.3chord).

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Prediction of Aerodynamic Characteristics of an Elliptic Airfoil at Low Reynolds Number

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2012-72389 ◽

2012 ◽

Cited By ~ 1

Author(s):

Varun Chitta ◽

D. Keith Walters

Keyword(s):

Experimental Data ◽

Reynolds Number ◽

Turbulence Models ◽

Leading Edge ◽

Aerodynamic Characteristics ◽

Transitional Flow ◽

Suction Surface ◽

Turbulent Models ◽

Lift And Drag ◽

Elliptic Airfoil

This study focuses on modeling the effects of transitional flow and surface curvature on aerodynamic characteristics of an elliptic airfoil. Numerical simulations have been performed on a 16% thick elliptic airfoil for a range of angle of attack (α) from 0° to 20° and flow Reynolds number (Re) of 3 × 105, using relatively new transition-sensitive and traditional fully turbulent eddy viscosity turbulence models. Test conditions were matched to experiments by Kwon and Park (2005) and numerical results were compared with available experimental data. Results indicate that the transition-sensitive models, namely k-kL-ω and Transition SST, accurately predict the laminar-to-turbulent transition locations and reproduce the laminar separation bubbles on the suction surface of the airfoil in agreement with the experimental data. Also, transition-sensitive models yield improved predictions of lift and drag performance when compared with results from fully turbulent models. The fully turbulent models; including SA and k-ω SST, and a newly developed curvature-sensitive model (SST k-ω-ν2) fail to capture the flow separation and reattachment locations near the leading edge of airfoil. However, the curvature-sensitive SST k-ω-ν2 model predicts the stall point of the airfoil close to experimental results, while all other tested RANS models failed to accurately predict the stall point. Taken as a whole, the results suggest that accurate aerodynamic predictions at both low and high angles of attack might be achieved by using a model that includes the effects of both transition and curvature.

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