32th Congress of the International Council of the Aeronautical Sciences

03.1 - Aerodynamics – CFD Methods and Validation


M. Li, No.2 High School of East China Normal University, China; H. Xu, Fudan University, China

The aerodynamic interactions are studied between the two NACA0012 airfoils in tandem with each airfoil being pitched at an angle of 4 degree and the Reynolds number being set at 104. The studies are based on the solutions of two-dimensional Navier-Stokes equations and the latest vortex identification method of Liutex. The time-averaged aerodynamic coefficient analysis clearly suggests that the rear airfoil gain an obvious aerodynamic advantage over the front airfoil, which provides the evidence to support the phenomenon of bird formation flight. Aside from the mean aerodynamic performance, the detailed interactions between the airfoils are studied in terms of the oscillations in the instantaneous coefficients. The Fourier Transformation is applied to study spectra of the periodically-fluctuating aerodynamic coefficients. Moreover, the oscillating mechanisms in the coefficients are well explained by the vortices identified by Liutex, which are constantly generated at the trailing-edge tips of the both airfoils and are induced by the complex aerodynamic interactions between the airfoils. The front airfoil interacts with the rear one by the vortex shedding from its trailing tip, giving rise to the “vortex pair” corridor that passes around the rear airfoil and induces the vortices on the upper surface of rear airfoil. In addition, the frequency contents are analysed in the aerodynamic coefficient harmonics. The findings enrich the current understandings of airfoil flows, in particular, the mechanisms of airfoil-vortex interactions.

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