Numerical Study of Aerodynamic Behavior of a Plunging Airfoil in Ground Effect

When a flying vehicle is approaching a watery or earthy surface, the flow pattern around it is changed that is called the ground or surface effect. In this study, the phenomenon of ground effect and its effects on aerodynamic coefficients and flow pattern around NACA0012 and LH37 airfoils are numerically investigated. The analysis is done for statically and dynamically airfoils with plunging motion at subsonic incompressible flow regime. The Navier-Stocks governing equations are used with k-𝜔 SST turbulence model. At first the effects of ground effect on lift coefficient of airfoils are studied in various distance from surface, statically. Then at each position of airfoils from the surface the lift coefficient behavior of airfoils at sinusoidal plunging motion with the specified amplitude and frequency is investigated. the statically results show that the lift coefficient of airfoils and pressure distribution over them are changed when they approach the surface with respect to far from it, which is seen as decreasing to a certain height and then increasing it. Dynamically analyzes also indicate a change in the oscillation amplitude of the lift coefficient and the existence of a phase difference at the points of achievement of minimum and maximum lift, when the airfoils are an approach to the surface. The streamlines also showed the changes in flow field patterns around the airfoils, when they approach the surface.