Vortex flow aerodynamics behind a symmetric airfoil at low angles of attack and Reynolds numbers

Abstract

The low Reynolds number aerodynamics is important to investigate for micro air vehicle applications. The current paper covers numerical simulations to present the downstream development of the wake patterns and detailed analysis of the vortices generated at the downstream of NACA 0012 airfoil around the critical angle of attack where the instantaneous vortex patterns are oscillatory and differ from the mean vortex pattern for low Reynolds numbers ranging from 1000 to 4000. The instantaneous and mean aerodynamic forces, pressure and skin friction coefficients, and vorticity values are compared in addition to the path of the vortex centers, their longitudinal and lateral spacings, Kármán spacing ratios, and distortion ratios at the wake of the airfoil in regard to the different Reynolds numbers investigated. The streamwise and crosswise velocities of the vortex cores and relative velocities at different transverse locations are also discussed and presented in detail. The correlations between different non-dimensional numbers (St, Re, Ro) are obtained at these low Reynolds numbers investigated.

An experimental study of the unsteady vortex structures of a clapping-wing micro air vehicle

“…9–11 Especially for flapping flight, the extraordinary flight capabilities of flyers benefit from their unique flow structures, this research field is called flapping-wing propulsion or inspired propulsion. 12–15 Flapping-wing propulsion, which leads to superior aerodynamic performance, is generally studied by means of numerical calculations and experiments. However, the numerical simulation of flapping flight involves high-frequency motion and flexible wings, which bring infinite challenges to achieving convergence.…”