"S65" (granthp)
09/23/2016 at 18:03 • Filed to: Corolla FX16 GT-S

Ask me questions to keep me entertained.

DISCUSSION (45)

ttyymmnn > S65
09/23/2016 at 18:07

What is the velocity of a laden swallow?

TheHondaBro > S65
09/23/2016 at 18:07

Did Adam and Eve have navels?

If a hen-and-a-half could lay an egg-and-a-half in a day-and-a-half, how long would it take a monkey with a wooden leg to kick all the seeds out of a dill pickle?

Why do we park in a driveway and drive on the parkway?

Why is the word “abbreviation” so long?

Why is there no “w” in “one”, but there is a “w” in “two” and we don’t use it?

How do you know when you have run out of invisible ink?

Why do kamikazes wear helmets?

Can you stake a vampire with an artificial heart?

How long is a piece of string?

What’s the best way to UN-teach a child to put a plastic bag on his/her head?

Are shart* and skid marks** caused by the same thing?

At a movie theatre You are asked, “ Hey, what are you doing here?”

Now that Microsoft is so big, should it be called Macrosoft?

You know that little indestructible black box that is used on planes? Why can’t they make the whole plane out of the same substance?

Why isn’t there mouse-flavored cat food?

Why isn’t phonetic spelled the way it sounds?

Why is the word dictionary in the dictionary?

Why is the time of day with the slowest traffic called rush hour?

Why is the third hand on the watch called a second hand?

Why is it that night falls but day breaks?

S65 > ttyymmnn
09/23/2016 at 18:08

o begin with, I needed basic kinematic data on African and European swallow species.

Although 47 of the 74 worldwide swallow species are found in Africa, 1 only two species are named after the continent: the West African Swallow ( Hirundo domicella ) and the South African Swallow ( Hirundo spilodera ), also known as the South African Cave Swallow.

Since the range of the South African Swallow extends only as far north as Zaire, 2 I felt fairly confident that this was the non-migratory African species referred to in previous discussions of the comparative and cooperative weight-bearing capabilities of African and European swallows. 3

left: South African Swallow
right: European Swallow

SpeciesBody massFrequencyAmplitudeZebra Finch13 g27 Hz11 cmEuropean Swallow20 g 18 Hz? 18 cm?Downy Woodpecker27 g14 Hz29 cmBudgerigar34 g14 Hz15 cm SpeciesWingspanFrequencyAmplitudeBudgerigar27 cm14 Hz15 cmEuropean Swallow 28–30 cm 14 Hz? 23 cm?Downy Woodpecker31 cm14 Hz29 cmEuropean Starling35 cm14 Hz26 cm Thanks to everyone who has written in with comments and questions. Responses are posted here , along with a revised estimate from Dr Graham Taylor, and some alternate theories .

Kinematic data for both African species was difficult to find, but the Barn or European Swallow ( Hirundo rustica ) has been studied intensively, and kinematic data for that species was readily available.

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A 54-year survey of 26,285 European Swallows captured and released by the Avian Demography Unit of the University of Capetown finds that the average adult European swallow has a wing length of 12.2 cm and a body mass of 20.3 grams. 4

Because wing beat frequency and wing amplitude both scale with body mass, 5 and flight kinematic data is available for at least 22 other bird species, 6 it should be possible to estimate the frequency ( f ) and amplitude (A) of the European Swallow by a comparison with similar species. With those two numbers, it will be possible to estimate airspeed (U).

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Actually, wrong. By comparing the European Swallow with bird species of similar body mass, we can estimate that the swallow beats its wings 18 times a second with an amplitude of 18 cm:

Note that even the tiny Zebra Finch flaps its wings no more than 27 times a second while cruising.

If we ignore body mass and look only at bird species with a similar wingspan, we can estimate an average frequency of 14 beats per second and an amplitude of 23 cm:

By averaging all 6 values, we can estimate that an average European Swallow flies at cruising speed with a frequency of roughly 15 beats per second, and an amplitude of roughly 22 cm.

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Last month’s article on The Strouhal Number in Cruising Flight showed how simplified flight waveforms that graph amplitude versus wavelength can be useful for visualizing the Strouhal ratio ( f A/U), a dimensionless parameter that tends to fall in the range of 0.2–0.4 during efficient cruising flight.

For a European Swallow flying with our estimated wingbeat amplitude of 24 cm, the predicted pattern of cruising flight ranges from a Strouhal number (St) of 0.2:

... to a less efficient 0.4:

If the first diagram (St = 0.2) is accurate, then the cruising speed of the European Swallow would be roughly 16 meters per second (15 beats per second * 1.1 meters per beat). If the second diagram (St = 0.4) is accurate, then the cruising speed of the European Swallow would be closer to 8 meters per second (15 beats per second * 0.55 meters per beat).

If we settle on an intermediate Strouhal value of 0.3:

We can estimate the airspeed of the European Swallow to be roughly 11 meters per second (15 beats per second * 0.73 meters per beat).

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Airspeed can also be predicted using a published formula. By inverting this midpoint Strouhal ratio of 0.3 ( f A/U 0.3), Graham K. Taylor et al. show that as a rule of thumb, the speed of a flying animal is roughly 3 times frequency times amplitude (U 3 f A). 5

We now need only plug in the numbers:

U 3 f A
f 15 (beats per second)
A 0.22 (meters per beat)
U 3*15*0.22 9.9

... to estimate that the airspeed velocity of an unladen European Swallow is 10 meters per second.

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With some further study, it became clear that these estimates are accurate, though perhaps coincidental.

An actual study of two European Swallows flying in a low-turbulence wind tunnel in Lund, Sweden, shows that swallows flap their wings much slower than my estimate, at only 7–9 beats per second:

“Compared with other species of similar size, the swallow has quite low wingbeat frequency and relatively long wings.” 7

The maximum speed the birds could maintain was 13–14 meters per second, and although the Lund study does not discuss cruising flight in particular, the most efficient flapping (7 beats per second) occurred at an airspeed in the range of 8–11 meters per second, with an amplitude of 90–100° (17–19 cm).

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Averaging the above numbers and plugging them in to the Strouhal equation for cruising flight ( f A/U = 7 beats per second * 0.18 meters per beat / 9.5 meters per second) yields a Strouhal number of roughly 0.13:

... indicating a surprisingly efficient flight pattern falling well below the expected range of 0.2–0.4.

Although a definitive answer would of course require further measurements, published species-wide averages of wing length and body mass, initial Strouhal estimates based on those averages and cross-species comparisons, the Lund wind tunnel study of birds flying at a range of speeds, and revised Strouhal numbers based on that study all lead me to estimate that the average cruising airspeed velocity of an unladen European Swallow is roughly 11 meters per second , or 24 miles an hour .

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For those looking for additional answers, the four capitals of Assyria were Ashur (or Qalat Sherqat), Calah (or Nimrud), the short-lived Dur Sharrukin (or Khorsabad), and Nineveh. 8 The ruins of all four ancient cities fall within the modern state of Iraq.

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Chris & Tilde Stuart
Birds of Africa: From Seabirds to Seed-Eaters
MIT Press (1999)

G. L. Maclean
Roberts’ Birds of Southern Africa
John Voelcker Bird Book Fund, Cape Town, South Africa (1985)

Graham Chapman, John Cleese, Eric Idle, Terry Gilliam, Terry Jones, Michael Palin
Monty Python and the Holy Grail
Python (Monty) Pictures Ltd. (1975)

Avian Demography Unit
SAFRING results of the European Swallow ( Hirundo rustica )
Department of Statistical Sciences, University of Cape Town (2002)

Graham K. Taylor, Robert L. Nudds, Adrian L. R. Thomas
Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency
Nature 425 , 707–711 (October 16, 2003)

Email correspondence with Graham Taylor of the University of Oxford Zoology Department (October 22–23, 2003)

Kirsty J. Park, Mikael Rosén, Anders Hedenström
Flight kinematics of the barn swallow (Hirundo rustica) over a wide range of speeds in a wind tunnel
The Journal of Experimental Biology 204 , 2741–2750 (2001)

Ashur Cherry
Assyrian History
The Mesopotamian Encyclopedia (2001)

Simplify, then add beer > S65
09/23/2016 at 18:08

If you got to design your own car a la the Powell “Homer”, what would be its defining characteristics?

S65 > TheHondaBro
09/23/2016 at 18:10

Probably

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ttyymmnn > S65
09/23/2016 at 18:11

How much wood could a woodchuck chuck if a woodchuck could chuck wood?

S65 > ttyymmnn
09/23/2016 at 18:12

More than a beaver

S65 > Simplify, then add beer
09/23/2016 at 18:14

Low, somewhat loud, crank windows on the passenger side, VVT, a japanese engine

ttyymmnn > S65
09/23/2016 at 18:17

A bus is driving down the road, and there are 14 passengers on board. At the first stop, 5 passengers get on and 6 get off. At the next stop, 3 passengers get on and 7 get off. At the third stop, 4 passengers get on and none get off. At the next stop, 8 passengers get on and 6 get off.

What is the bus driver’s name?

S65 > ttyymmnn
09/23/2016 at 18:19

are u trying to get me to do math for your kid again

ttyymmnn > S65
09/23/2016 at 18:21

Yes. Please show your work.