Mean flow characteristics of two-dimensional wings in ground effect

Abstract

The present study numerically investigates the aerodynamic characteristics of two-dimensional wings in the vicinity of the ground by solving two-dimensional steady incompressible Navier-Stokes equations with the turbulence closure model of the realizable k-<TEX>${\varepsilon}$</TEX> model. Numerical simulations are performed at a wide range of the normalized ground clearance by the chord length (<TEX>$0.1{\leq}h/C{\leq}1.25$</TEX>) for the angles of attack (<TEX>$0^{\circ}{\leq}{\alpha}{\leq}10^{\circ}$</TEX>) in the prestall regime at a Reynolds number (Re) of <TEX>$2{\times}10^6$</TEX> based on free stream velocity <TEX>$U_{\infty}$</TEX> and the chord length. As the physical model of this study, a cambered airfoil of NACA 4406 has been selected by a performance test for various airfoils. The maximum lift-to-drag ratio is achieved at <TEX>${\alpha}=4^{\circ}$</TEX> and h / C = 0.1. Under the conditions of <TEX>${\alpha}=4^{\circ}$</TEX> and h / C = 0.1, the effect of the Reynolds number on the aerodynamic characteristics of NACA 4406 is investigated in the range of <TEX>$2{\times}10^5{\leq}Re{\leq}2{\times}10^9$</TEX>. As Re increases, <TEX>$C_l$</TEX> and <TEX>$C_d$</TEX> augments and decreases, respectively, and the lift-to-drag ratio increases linearly.