Low-aspect-ratio wings for wing-ships

Flying in ground poses technical and aerodynamical challenges. The requirements for compactness, efficiency, maneuverability, off-design operation, open new areas of investigations in the field of aerodynamic analysis and design. A review of the characteristics of low-aspect ratio wings, in and out-of-ground, is presented. It is shown that the performance of such wings is generally inferior to that of slender wings, although in ground placement can yield substantial improvements in the aerodynamic efficiency. The use of tip devices, such as winglets and endplates, or an appropirate tip design, can change substantially the characteristics of the wing. Thin and thick airfoil sections are designed in ground effect, by using a multipoint inverse design method based on conformal mapping, to perform best either at constant lift or at increasing ground clearance. Three-dimensional computations have been performed with a panel code (VSAERO), and compared with available experimental data at aspect-ratios as low as 1. Wings of aspect-ratio 1.5 to 2.5 having the airfoil sections presented in this work have been computed at various ground clearances. It is concluded that design in ground effect is possible, and that the existing computational methods are adequate for an approximate study of low-aspect-ratio wings, although many flow phenomena require detailed investigastions.