Effects of Anhedral and Dihedral on a 75-deg Sweep Delta Wing

Abstract

An investigation into the effects of spanwise camber in the form of anhedral and dihedral on a 75-deg sweep delta wing is detailed. Data are presented encompassing force balance, surface pressure measurement, seven-hole probe surveys, and vortex burst trajectories. The results show that the net effect of this form of nonplanarity is an increase in lift for anhedral and a decrease in lift for dihedral compared to the planar wing. Small anhedral angles are most effective in augmenting lift. Anhedral does not appear to greatly augment the strength of the leading-edge vortex. The major bene t from anhedral would appear to be due to its displacing effect on the vortex trajectory: drawing the vortex closer to the wing surface and inboard compared to the planar wing. As the vortex is drawn inboard, its induced surface loading acts on a greater area of the wing. Dihedral also draws the vortex closer to the wing surface (to a greater extent then anhedral) while moving the vortex toward the wing leading edge. In addition, anhedral does not appear to introduce any detrimental effects on longitudinal stability and does not incur any penalties in terms of vortex burst characteristics. Nomenclature C D min = minimum drag coef cient C L = lift coef cient C N = normal force coef cient C pt = maximum stagnation pressure loss C T = leading-edge thrust coef cient c r = wing root chord k = wing ef ciency parameter k P = potential lift constant q = freestream dynamic pressure r = radial coordinate, measured from vortex center line s = local semispan U = freestream velocity V A = axial velocity V h = rotational velocity v, w = spanwise velocity, vertical velocity normal to wing surface x, y, z, y 0 , z 0 = Cartesian coordinates, y 0 and z 0 orientated at u a = wing centerline incidence C = vortex circulation K = wing leading-edge sweep angle u = wing dihedral angle, de ned (¡ ) for anhedral, (+ ) for dihedral x = axial vorticity Subscripts max = maximum min = minimum np = nonplanar pr = projected

Examination and Prediction of the Lift Components of Low Aspect Ratio Rectangular Flat Plate Wings

“…Numerous comparisons validating this approach are present in the literature, especially with application to delta wings [3,[10][11][12][13][14][15]. Slender rectangular wings have also been modeled using the leading edge suction analogy; with terms associated with vortex lift caused by the leading edge and side edges [3,11].…”