Effect of ground on aerodynamics and longitudinal static stability of a non-slender delta wing

Abstract

In this paper, the effect of ground on aerodynamics and longitudinal static stability of a non-slender delta wing with sweep angle of 45 degree and thickness-to-chord ratio (t/c) of 5.9% was characterized at Reynolds number of 9×104 in a low-speed wind tunnel using force and pressure measurements. The measurements were conducted for angles of attack varying between 0≤α≤30 degrees and non-dimensional heights between 3%≤h/c≤107% and height stability of the wing based on aerodynamic center in pitch (Xa) and aerodynamic center in height (Xh) was constructed. The results indicate that the effect of ground has substantial impact on both aerodynamic performance and stability of the delta wing. As the height of the wing decreases, both drag and lift forces increases where these effects were observed to be more pronounced for higher angles of attack. The maximum aerodynamic performance with increasing ground effect intensity was measured around 7 degree. Center of pressure (Xp) as well as Xa travel in a limited range over the wing chord, whereas Xh exhibits back and forth movement on the longitudinal axis resulting in interchanging stability characteristics varying with both height and angle of attack. The pressure measurements showed that the effect of ground has significant and complex impact on both vortex reattachment and vortex strength with varying angles of attack and heights such that it might promote reattachment and increases vortex strength but might cause earlier stall.