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October 31, 2019 Dave Santos
Thank you, Joe. Thanks also to R.Borobia-Moreno, D.Ramiro-Rebollo, G.Sanchez-Arriaga and R.Schmehl for
the analytic and experimental work that rigorously revealed the
anomalous aerodynamic parameter, that any of several scholars or
aerodynamicists in kite circles could also have identified as Vortex
Lift, given the same prompting. Kite science is advancing as old loose
ends and open questions resolve by the accumulated terrific efforts of
so many.
As
case notes, Brasington's best-of-kite-store Ninja turbine crab-claw
design (used for KiteSat7) is clearly vortex lift enhanced, and large
birds commonly land with each wing bent in a delta-form, developing high vortex-lift for
optimal final deceleration. The top advantage of vortex lift in AWE is
best low wind performance, to keep flying as other wings struggle and
fall
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October 30, 2019 Dave Santos
Kite Vortex Lift Aerodynamic Parameter Identification
It
was a popular scientific paradox generations ago, that bumblebee flight
was "impossible" under standard aerodynamic theory. It slowly came to
light how many insects develop extra lift by powerful Vortex Lift on
their wings, and so do bats, hummingbirds, and many other birds. A
useful new flight regime based on vortex lift of strakes and delta
wings at high angles of attack slowly was slowly perfected in both
fighter jets and delta kites. The Concord and Space Shuttle landed by
enhanced vortex lift. The NASA Power Wing (NPW) is a soft single-skin
(SS) delta kite with vortex lift enhancement.
Kites
have long been known to operate effectively at high AoA, and associated
vortex lift is readily attributable to the common swept surfaces and
turbulating features of classic kite designs.
The
kite vortex lift aerodynamic parameter is often misleadingly identified
as "stall", because classic stall of a long wing causes an abrupt loss
of lift and control, but vortex lift of a stubby swept wing actually
increases well beyond normal critical angles, and stability is
typically enhanced. Bumblebee aside, the funny thing is that vortex
lift is also identifiable as as frontal drag; but in the inclined
airframe reference frame, aligned
in the normal lift direction, its lift.
==========================
Extending
the analysis of kite vortex lift solves an interesting observed power
kite flight anomaly. If one tries to hold a high-AR high-L/D hot power
kite static, stalled low in the window, its very hard to control and
the kite tends to fall down. At the same time, many a low-AR low-L/D
traditional kite will just hang there happily. Obviously the
traditional kite is using vortex lift that the hot kite cannot. This is
bad news for hot kiteplanes in weak fluky wind.
We
can now effectively identify the NPW as a soft delta kite, by its
projected plan-form, that therefore develops strong vortex lift. This
explains the anomalous excellent performance of the NPW compared to
more complex more expensive power kites. It was a revelation at
NABX2007 that the poor kite buggy pros with NPWs were competitive with
expensive hot power kites. Each kite had its superior characteristic
modes (see old discussions) and the general outcome was rough parity
across all conditions. NASA developed the NPW 50yrs ago for maximal
power-to-weight for space missions, and its still a top wing, by both
vortex lift power and SS construction.
Furthermore, and this is new domain art, vortex lift is apparently a key aerodynamic
parameter of high turning rate of low-AR stunt and power kites. High-AR
race wings dominate in max crosswind velocity, but not max power, and
turn quite slowly and loosely compared to the low-AR wings. The common
LEI freestyle power kite has considerable planform sweep, and
associated vortex lift, for fast turn-rate in tight turns. Vortex lift
also explains which kites best maintain high power in tight turns.
================
"The full state vectors of the
three kites were reconstructed and a data set with the aerodynamic
force and torque, angle of attack and side slip angle for different
maneuvers was created. However, difficulties arose for the aerodynamic
parameter identification because the kites spent most of the time in a
post-stall state during the flight."
AWEC2019- Flight Testing,
Aerodynamic Parameter Identification, and Dynamic Simulation of Rigid
and Flexible Kites Applied to Airborne Wind Energy Systems
R.Borobia-Moreno1,2,D.Ramiro-Rebollo1,G.Sanchez-Arriaga1,R.Schmehl3
1UniversidadCarlosIIIdeMadrid,Spain,
2NationalInstituteofAerospaceTechnology,Spain
3DelftUniversityofTechnology,TheNetherlands
================
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Vortex
lift
Vortex
lift works by capturing vortices generated from the sharply swept
leading edge of the wing. The vortex, ...
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Stall
(fluid dynamics)
Stalls
in fixed-wing flight are often experienced as a sudden reduction in
lift as the pilot increases the wing'...
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================
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USC
- Viterbi School of Engineering - Leading Edge Vortex Allows Bats to...
USC
- Viterbi School of Engineering
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It
was a popular scientific paradox generations ago, that bumblebee flight
was "impossible" under standard aerodynamic theory. It slowly came to
light how many insects develop extra lift by powerful Vortex Lift on
their wings, and so do bats, hummingbirds, and many other birds. A
useful new flight regime based on vortex lift of strakes and delta
wings at high angles of attack slowly was slowly perfected in both
fighter jets and delta kites. The Concord and Space Shuttle landed by
enhanced vortex lift. The NASA Power Wing (NPW) is a soft single-skin
(SS) delta kite with vortex lift enhancement.
Kites
have long been known to operate effectively at high AoA, and associated
vortex lift is readily attributable to the common swept surfaces and
turbulating features of classic kite designs.
The
kite vortex lift aerodynamic parameter is often misleadingly identified
as "stall", because classic stall of a long wing causes an abrupt loss
of lift and control, but vortex lift of a stubby swept wing actually
increases well beyond normal critical angles, and stability is
typically enhanced. Bumblebee aside, the funny thing is that vortex
lift is also identifiable as as frontal drag; but in the inclined
airframe reference frame, aligned
in the normal lift direction, its lift.
================
"The full state vectors of the
three kites were reconstructed and a data set with the aerodynamic
force and torque, angle of attack and side slip angle for different
maneuvers was created. However, difficulties arose for the aerodynamic
parameter identification because the kites spent most of the time in a
post-stall state during the flight."
AWEC2019- Flight Testing,
Aerodynamic Parameter Identification, and Dynamic Simulation of Rigid
and Flexible Kites Applied to Airborne Wind Energy Systems
R.Borobia-Moreno1,2,D.Ramiro-Rebollo1,G.Sanchez-Arriaga1,R.Schmehl3
1UniversidadCarlosIIIdeMadrid,Spain,
2NationalInstituteofAerospaceTechnology,Spain
3DelftUniversityofTechnology,TheNetherlands
================
|
|
|
Vortex
lift
Vortex
lift works by capturing vortices generated from the sharply swept
leading edge of the wing. The vortex, ...
|
|
|
|
|
|
Stall
(fluid dynamics)
Stalls
in fixed-wing flight are often experienced as a sudden reduction in
lift as the pilot increases the wing'...
|
|
|
================
|
|
|
USC
- Viterbi School of Engineering - Leading Edge Vortex Allows Bats to...
USC
- Viterbi School of Engineering
|
|
|
|