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Dragonfly Flight
June 28, 2021
Childhood is difficult enough without the
misinformation acquired from your
child peers. One
tall tale I heard as a child was the
myth that
dragonflies,
colloquially called
darners, could
sew your
eyes,
ears, and
lips shut. Thus myth was
promulgated by
European parents as a warning to their children that this could happen as they
slept as
punishment for
mischief.[1] Today's parents are not that
sinister. The best they can do is an
elf-on-the-shelf.
Dragonfly, from the archives of publisher, Pearson Scott Foresman.
(Wikimedia Commons image. Click for larger image.)
The darner dragonfly, (
Kingdom,
Animalia ;
Phylum,
Arthropoda;
Class,
Insecta;
Order,
Odonata;
Suborder,
Epiprocta;
Family,
Aeshnidae) looks like something from a
nightmare. They have large
compound eyes, each composed from 24,000
segments, that are
reminiscent of those of the
film monster,
Mothra.[2]
Fossils of dragonfly
ancestors with
wingspans of about three quarters of a
meter are found from the
Upper Carboniferous Period, about 325
million years ago. Dragonflies have two pairs of strong,
transparent wings and an elongated
body of bright
iridescent or
metallic colors created by
structural coloration, as in the iridescent coloration of
butterfly wings.
Dragonflies are of interest to developers of
micro air vehicles, since they are
agile fliers that are capable of sudden changes in
direction; in fact, they can move in all six
spatial directions,
forwards, backwards, left and right, and upwards and downwards. Their wings are capable of
effortless gliding, and one dragonfly mode of flight is gliding for a few seconds in between bursts of
powered flight. Dragonflies have a high
power/weight ratio, they can
accelerate at nearly 9
G, have a maximum
speed of about 30
miles per hour (50
kilometers per hour), and they
cruise at about 10 miles per hour (15 kilometers per hour), moving about a hundred body-lengths per second in forward flight.
A team of
researchers from the
University of South Australia (Mawson Lakes, Australia), the
Defence Science and Technology Group (Melbourne, Australia), and the
Universiti Putra Malaysia (Kembangan, Malaysia) has just published an
open access paper in the
journal,
Drones, on
biomimetic drones inspired by dragonflies.[3-4] They discuss how
flapping wing drones inspired by dragonflies are efficient in agile modes of flight, and they analyzed the fundamental principles of dragonfly flight to apply the principles of flapping wing
organisms to flapping wing drones.[3] The conclude that an optimal flapping wing drone,
efficient in all flight modes with high performance, would resemble a dragonfly.[3]
The
research team of
PhD candidates was led by
Javaan Chahl, a
professor of
Sensor Systems at the University of South Australia. The research, which was conducted
remotely during the
2020 COVID-19 lockdown, involved the students doing
mathematical analysis and
digitization of
stereo photographs of insect wings into
3D models, as well as
Rapid prototyping and
testing components for flapping wing drones.[4] Their goal was to match a dragonfly's extraordinary skills in
hovering, cruising, and
aerobatics.[4] Chahl explains that the dragonfly is an
apex insect flier,
"Dragonflies are supremely efficient in all areas of flying. They need to be. After emerging from under water until their death (up to six months), male dragonflies are involved in perpetual, dangerous combat against male rivals. mating requires an aerial pursuit of females and they are constantly avoiding predators. Their flying abilities have evolved over millions of years to ensure they survive... They can turn quickly at high speeds and take off while carrying more than three times their own body weight. They are also one of nature's most effective predators, targeting, chasing and capturing their prey with a 95 per cent success rate."[4]
Two wing examples from different dragonfly families. (Javaan Chahl/University of South Australia image. Click for larger image.)
Dragonflies are notoriously difficult to
capture in a
pristine state; and, since
museum specimens are too
fragile to be removed from their cases, the research team developed an
optical technique to photograph the wing
geometry of 75 different dragonfly species through the
glass display cases in museum collections.[4] They then modeled both the dragonfly body shape and
aerodynamic properties to understand their excellent flying abilities.[3-4] Says Chahl, "Dragonfly wings are long, light and rigid with a high lift-to-drag ratio which gives them superior aerodynamic performance... Their long
abdomen, which makes up about 35 per cent of their body weight, has also evolved to serve many purposes... It helps with
balance,
stability and
maneuverability. The abdomen plays a crucial role in their flying ability."[4]
Left, a comparison of aerodynamic lift and drag of corrugated and flat wings versus attack angle at a Reynolds number of 22 × 103. A corrugated wing provides substantially better aerodynamic performance than a flat wing. Right, a flapping wing mechanism made using a 3D printer in a student's home laboratory. (Left image, portion of fig. 7 of ref. 3, licensed under a Creative Commons Attribution License. Right, a University of South Australia image.)
The researchers conclude that future flapping wing drones will probably resemble the insect in shape, wings and
actuation.[4] They would be useful in the collection and delivery of awkward, unbalanced loads, an they can operate as agents in long
surveillance missions.[4]
A conceptual image of a 20 centimeter wingspan biomimetic dragonfly drone in flight. It was found that large, directly driven, corrugated wings are as efficient as fixed wings on drones with a much larger wingspan.
The abdomen, which contains a fuel cell energy source, also acts as a rudder and ballast.
(Fig. 15 of ref. 3, modified for clarity, licensed under a Creative Commons Attribution License.)
References:
- Friday 5: Scary Myths About Dragonflies, dragonflywoman web site, November 2, 2012.
- Mothra (1961, Ishirô Honda, Director) on the Internet Movie Database.
- Javaan Chahl, Nasim Chitsaz, Blake McIvor, Titilayo Ogunwa, Jia-Ming Kok, Timothy McIntyre, and Ermira Abdullah, "Biomimetic Drones Inspired by Dragonflies Will Require a Systems Based Approach and Insights from Biology, Drones, vol. 5, no. 2 (March 27, 2021), https://doi.org/10.3390/drones5020024. This is an open access publication with a PDF file here.
- Future drones likely to resemble 300-million-year-old flying machine, University of South Australia Press Release, April 27, 2021.
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