Numerical Study of Flapping-Wing Flow Physics in Nonuniform Freestream Using the High-Order Spectral Difference Method on Dynamic Unstructured Grids

Abstract

In this paper, a numerical study is conducted to understand the impact of nonuniform freestream on the aerodynamic performance of a flapping foil. Specifically, an unsteady flow environment is generated by stationary inline or staggered circular cylinder arrays upstream. A 2D NACA0012 airfoil is then placed at different locations downstream of the cylinder arrays, and oscillates in the nonuniform freestream. Unsteady flows over the flapping foil are numerically simulated by solving the 2D low-Mach-number-preconditioned compressible Naiver-Stokes equations on deformable unstructured grids using the high-order spectral difference method. The flow fields over a pitching airfoil in unsteady flow environments and the corresponding aerodynamic forces are analyzed and compared under different flow conditions. It is observed that the nonuniform freestream can significantly affect the unsteady vortex dynamics of a flapping foil, thus modifying the thrust and lift generation.

Computational Study of Flapping Wing Response to Vertical Gusts at Low Reynolds Numbers

“…This limited their ability to create a stepfunction-like gust, which would simulate a MAV flying into an updraft wider than the vehicle itself. The numerical studies over the pitching airfoil in unsteady flow environments significantly affect the aerodynamic performance of the flapping wing by modifying the vortex structures 13 . High-order CFD methods had been proven more accurate and efficient to capture the complex vortex-dominated flow structures due to flapping wings 14 .…”