| An experimental and theoretical investigation into the effects of spanwise camber on delta wings is described. Twenty four flat plate delta wings, encompassing various spanwise camber variations were examined. Testing comprised force balance, surface pressure measurement, 7-hole probe surveys, on-surface flow visualization and measurement of vortex burst trajectories. The low speed experimental investigation was conducted in Texas A&M University's 3’ x 4’ low speed wind tunnel and a 2’ x 3’ water tunnel. Theoretical methods developed include an explicit analytic method to predict the lift of spanwise cambered delta wings of constant camber, as well as various other methods to predict the characteristics of vortex flows and their effects on delta wing aerodynamics. The investigation shows that the net effect of non-planarity is an increase in lift for anhedral and a decrease in lift for dihedral compared to the planar wing, with these effects increasing with wing sweep. Consequently, anhedral shows the greatest benefit for most applications. Small anhedral angles are most effective in augmenting lift. Anhedral increases wing efficiency over a comparative planar wing. Anhedral does not, appear to greatly augment the strength of the leading edge vortex as demonstrated by data detailing vortex circulation and from peak surface loading from surface pressures. The major benefit from anhedral would appear to be due to its displacing effect on the vortex trajectory: both drawing it closer to the wing surface and inboard. As the vortex is drawn inboard, its induced surface loading acts on a greater area of the wing. 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. Somewhat surprisingly, although limited in scope, the present variations in the distribution of spanwise camber suggest that camber is most beneficial applied near the wing tips: as is the case for unswept wings. It must be cautioned, however, that this may only be true for the range of configurations evaluated in the present study. |
