Aerodynamic Interactions and Ground Effect in 2-D Slightly Viscous Unsteady, Vorticity-Dominated Flows

MARCELO FEDERICO VALDEZ; SERGIO PREIDIKMAN; JOSE ENRIQUE STUARDI

Isla Margarita

Congreso; CIMENICS 2008 - IX International Congress on Numerical Methods in Engineering; 2008

Sociedad Venezolana de Métodos Numéricos en Ingeniería (SVMNI)

The flight of insects is dominated by nonlinear ('nonlinear' refers to quantities that can only be described by nonlinear equations) unsteady aerodynamic mechanisms. Their flapping wings offer unique advantages over conventional fixed and rotary wings. Among these are de generation of lift and thrust at minimal body weight. Although the flight of insects and small birds occurs at small chord-based Reynolds numbers, it is still reasonable to assume that viscous effects are restricted to boundary layers on the surfaces of the wings and that vorticity is restricted to those boundary layers and wakes. This hypothesis justifies the use of a modified version of the general unsteady vortex-lattice method (UVLM) that accounts for the possibility of leading-edge separation. In this work, the unsteady aerodynamic interaction between two profiles immersed in an infinite two-dimensional fluid is investigated. An important, but little studied aspect of small-scale flapping-wing flight, the effect of the ground on aerodynamic characteristics, is also investigated. Ground effect is usually studied in one of two ways: the first uses mirror images of the wings and their wakes to make the ground a plane of symmetry; the second panels the ground as well as the wings and their wakes. The former is convenient, but limited to simulating flight near a plane surface. The latter is less convenient, but more appealing because it is capable of simulating flight over irregular contours. In the present simulations, the profiles imitate the typical flapping motion of insects and small birds. The final goal of this work is to contribute a numerical tool for evaluating aerodynamic interactions (often called interference), including ground effect, to support the development of super-maneuverable un-crewed air vehicles (UAVs) powered by flapping wings.