Early experimenters had observed that a wind tunnel model of square planform (AR=1) stalled at an extremely high angle of attack (greater than 40 degrees). In 1911 Handly-Page verified the late stall of extremely low aspect ratio wings and discovered that this phenomenon was due to the large tip vortices forcing the potential flow at the root of the wing to remain attached. Although there is some extra lift at the high AoA these wings can achieve, it's not as much as one might expect from the angle of attack . The reason being that these wings lose lift at the tips, just like higher aspect ratio wings, and the lift increment per degree becomes smaller as AR decreases (low delta CL / degree alpha). They also have higher induced drag than a more conventional AR wing which means, given the same wing area and power loading, reduced climb performance. Several experimental airplanes with extremely low AR wings have demonstrated good cruise performance and slow landing speed but, as far as I know, none has gone into production. I haven't included a page dealing with this type yet, Check these URLs if you're interested in extremely low AR ( 1 2 3 4 5 6 7 8 )
Throughout the 1930s Alexander Lippisch was developing His "Delta" series of airplanes. These were characterized by swept back leading edges with a straight, unswept, trailing edge and the root chord nearly equal to the fuselage length. In the early 1940s Lippisch and a group of students from the universities of Darmstadt und Munich began working on high speed flight. The delta plan form was selected because the long root chord allowed a deep spar in an aerodynamically thin airfoil and, by setting the leading edge sweep angle to be greater than the Mach angle at cruise speed, the leading edge can remain free of drag inducing shock waves. In '42 this group observed that a model with 60 degrees LE sweep exhibited later stall and more lift than contemporary potential flow airfoil theory predicted. This model (the Li-P13) became the basis for the DM-1 which never operated as a free flying aircraft but did see considerable wind tunnel testing in America after W.W.II. By the end of the 1940s several of the world's air forces were requesting bids to build supersonic fighters, and many of the new designs had simple delta planforms.
However a simple delta wing is not the most versatile planform and, by the mid '50s, there were a few "deltawing" planes that deviated from the pure triangle. The first such improvement on the delta was a little technology demonstrator from Saab called the 210. The Saab 210's wing was composed of two superimposed triangles, an inner panel with 80 degrees sweep which produced a stable vortex system, and an outer panel with 57 degrees sweep which further strengthened the vortex and also improved low speed control by increasing the aspect ratio. The trapezoidal wing with strakes, seen on most modern fighters, is an evolution of the double delta.
Using, mainly, simple drawings accompanied be minimal explanatory
text I'll try to give a basic insight into the methods of vortex
Anatomy of a vortex
Kline Fogleman stepped airfoils
Witold Kasper Superstall
Highly swept wings
The Saab experiment Spanwise blowing
Bibliography and miscellaneous links
As time and inclination permit I will be adding material to these pages. Comments and criticisms are welcome, pleas don't hesitate to drop me a line
Credit: While I was collecting data for this page the guys on the Nurflügel mailing list provided much helpful advice and leads on documents. Several of the topics that they suggested have not been incorporated yet because, frankly, this stuff is hard.
Disclaimer: These documents are intended as an introduction to the subject of vortex augmented lift. If you're working on your master's thesis in fluid mechanics this will look pretty simplistic to you. If you are a high school physics student, or an aeromodeler, then this page is for you.