Review of Delta Wing History and Science in AWE Context

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Nov. 2, 2019                         Dave Santos

Re:  Review of Delta Wing History and Science in AWE Context

Bingo, this is a 1966 NASA delta-wing reference that accurately presents delta vortex lift insight, with close agreement of formal prediction and experimental data. Most pertinent is the data over a wide AR range. Kiter's know that the right-triangle delta is the best overall trade-off between higher and lower AR (~AR3), and here we have numbers to help explain that. Up to a point, higher AR boosts Cl helpfully, but once AR goes too high at high AoA, a wing becomes too unstable to effectively control, and Cl starts to drop again. At zero AoA, there is no vortex lift. For AWES, the widest possible match of variable load and wind conditions is enabled by vortex lift. Highest steady-state L/D is not as compliant a basis for kite power.

NASA Technical Note   TN D-3767
By Edward C. Pohamus, Langley Research Center, Langley Station, Hampton, Virgina
December 1966
November 1, 2019                      Dave Santos

Re:  Review of Delta Wing History and Science in AWE Context

State of the art simulation graphics-
At this high AoA, without a large empennage, a high-AR flying wing would be dangerously unstable.  
High AoA on Delta
October 31, 2019                        Dave Santos

Review of Delta Wing History and Science in AWE Context
Seeking photo credit

Many traditional Asian kites are delta or diamond shaped, so the design history goes far back. In the case of insects, many moths have an iconic delta posture visible at rest and applied in evasive flight. The modern delta kite is the perfection of the architype. In formal AWE aerodynamic research, the delta has been largely overlooked in favor of long conventional wings. Current Vortex Lift Aerodynamic Parameter discussion fills gaps in the advancing kite engineering science. Wikipedia continues to advance as well, consistent with many early AWES Forum insights: On Delta Wings-

"(Delta wings) proved suitable for high-speed subsonic and supersonic flight. At the other end of the speed scale, the Rogallo flexible wing proved a practical design for the hang glider and other ultralight aircraft...The delta form brings unique structural advantages and aerodynamic characteristics...The long root chord of the delta wing, and minimal structure outboard, make it structurally efficient. It can be built stronger, stiffer and at the same time lighter than a swept wing of equivalent lifting capability. Because of this it is easy and relatively inexpensive to build...As the angle of attack increases, the leading edge of the wing generates a vortex which energizes the flow on the upper surface of the wing, delaying flow separation, and giving the delta a very high stall angle.[1] A normal wing built for high speed use typically has undesirable characteristics at low speeds, but in this regime the delta gradually changes over to a mode of lift based on the vortex it generates, a mode where it has smooth and stable flight characteristics. "

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