Experiencing Naruto whirlpools
by Hubert CHANSON (h.chanson@uq.edu.au)
M.E., ENSHM Grenoble, INSTN, PhD (Cant.), DEng (Qld), Eur.Ing., MIEAust., MIAHR, 13th Arthur Ippen awardee (IAHR)
Professor in Civil Engineering, The University of Queensland, Brisbane QLD 4072, Australia
Detailed photographs
Related links

Whirlpool at Naruto Presentation
The Merriam-Webster's Collegiate Dictionary states that a whirlpool is "water moving rapidly in a circle so as to produce a depression in the centre into which floating objects may be drawn". Basically a whirlpool is a vortex of vertical axis, with a downward velocity component near its centre. A good example is the bathtub vortex. VAN DYKE ([1], p. 59) presented a superb illustration. A related example is the vortex dropshaft design.

In coastal zones, whirlpools are produced by the interaction of rising and falling tides. They are often observed at the edges of straits with large tidal currents. (At Naruto, currents of up to 9 knots were observed.) The vortex (whirlpool) is a coherent structure typical of shear flows where there is a velocity difference across the shear layer. It affect the surrounding flow and water can be seen going back and forth across the shear layer between vortices.

Notable oceanic whirlpools include those of Garofalo along the coast of Calabria in southern Italy, and of Messina in the strait between Sicily and peninsular Italy, the Maelstrøm (from Dutch for "whirling stream") located near the Lofoten Islands off the coast of Norway (Table 1). Whirlpools near the Hebrides and Orkney islands, and in the Naruto strait between Awaji and Shikoku islands, are also well known.

Whirlpools in the world
Whirlpools are sometimes called Maelstrom, after the Norwegian current. The Maelstrøm is a strong tidal current of the Norwegian Sea in the Lofoten islands [2]. Flowing between the islands of Moskenesøya (North) and Mosken (South), it has a treacherous current. Strong local winds make the passage additionally dangerous. The word maelstrom entered the English language via fiction novelists who exaggerated the current of the channel into a great whirlpool (1). On English, the word "maelstrom" designates a large, fatal whirlpool, engulfing vessels and men, or a figurative application of the idea.

In Western Scotland, the Corryvreckan whirlpools are said to be "one of the most notorious stretches of water anywhere around the British Isles" (2).  The whirlpools are caused by a sudden rise of the seafloor in the strait.

Whirlpool at Naruto
Naruto whirlpools
The Naruto Strait (Naruto kaikyo) connects the Awaji and Shikoku islands. The strait is 1.3 km wide. The tide is semi-diurnal and the tidal range may be up to 1.7 m. The differences in tidal levels across the strait may reach 1.5 m with current speds exceeding 9 knots (4.6 m/s) on the Northern part of the Strait [3]. The notorious "whirlpools" (uzu-maki) take place on the Southern side of the Strait at the peak of the flow and ebb currents. The flow and ebb are also called southward and northward currents respectively.

Hubert CHANSON visited the Naruto whirlpools on Wednesday 17 October 2001 [4]. The meteorological conditions were poor because the centre of Typhoon No. 21 was located few hundreds kilometres South of Japan. The ebb current was maximum around 12:20 pm (3). The waters flowed from the Inland Sea (Setona Kai) to the Pacific Ocean. The whirlpools were best seen next to the Southern bridge pier (4). He experienced the whirlpools between 10:45 am and 12:45pm, first from the Ohnaruto bridge walkway (uzu-no-michi) (5) (6) and later in a boat. The bridge walkway is about 45 m above the sea level and reaches 450 m from the bridge abutment. From the bridge, the writer saw a freighter which became trapped in the whirlpools and vortices, and got stranded (grounded) beneath the bridge around 11:00 am. (The boat was still grounded 2 hours later, waiting for the next high tide.)

Figure A shows whirlpools and vortices on the Southern end of the Strait (right side when looking into the flow direction). The main current flows on the left of the vortices. The photograph was taken from 45 m above the sea, about 450 m from the bridge abutment. Figure B shows a street of vortices with a freighter in the background. Although the turbulence appears less intense, the ship was subjected to a faster current and to the effects of large-size cauldrons. Figure C presents the same freighter with a large size eddy (diameter larger than 50 m) downstream of the whirlpools. Figure D (Naruto12.jpg) shows a single whirlpool, view from upstream and above. Figure E & Figure F are views from downstream. In Figure E and Figure F, a whirlpool is visible in the foreground of the photograph. A grounded freighter (green hull), stranded next to the bridge pier, is visible in the background. In Figure E, a white tourist boat is coming around the Cape to view the whirlpools.
Whirlpool at Naruto Discussion
Whirlpools are basically two-dimensional vortical structures occurring in a turbulent developing shear layer. Such a flow may be approximated by a series of vortices of identical rotational direction advected downstream. (In first approximation the advection velocity is equal to half the main stream velocity.) Each vortex is affected by the movement of the fluid due to the other vortices. Considering a pair of vortices, they will turn around each around while being advected downstream. (Far away the vortex pair is seen as an unique vortex of strength equal to twice the strength of one vortex.) In real turbulent flows, the vortices may collapse and form a new larger vortex of stronger strength and identical rotation direction (i.e. vortex pairing). Vortex pairing may be repeated downstream and could yield very-large scale eddy structures. The process is sometimes called an inverted cascade of vortices (7). It may be repeated further downstream and this yields large vortical structures (e.g. Photo No. 2).


(1) For example, Jules VERNE (1828-1905) in "Vingt mille lieues sous les mers" first published in 1869-1870 in the magazine "Magasin d'Éducation et de Récréation" :
"«Maelstrom! Maelstrom!» s'écriait-il!
Le Maelstrom! Un nom plus effrayant dans une situation plus effrayante pouvait-il retentir à notre oreille? Nous trouvions-nous donc sur ce dangeureux parages de la côte norvégienne? Le Nautilus était-il entraîné dans ce gouffre, au moment où notre canot allait se détacher de ses flancs?
On sait qu'au moment du flux, les eaux resserées entre les îles Feroé et Loffoten sont précipitées avec une irréristible violence. Elles forment un tourbillon dont aucun navire n'a jamais pu sortir. De tous les points de l'horizon accourent les lames monstrueuses. Elle forme ce gouffre justement appelé le «Nombril de l'Océan», dont la puissance d'attraction s'étend jusqu'à une distance de quinze kilomètres. Là sont aspirés non seulement les navires, mais les baleines, mais aussi les ours blancs des régions boréales.
C'est là que le Nautilus - involontairement ou volontairement peut-être -, avit été engagé par son capitaine. Il décrivait une spirale dont le rayon diminuait de plus en plus. ..."
(2) A full article on the Corryvreckan whirlpools is at {http://www.smithsonianmag.si.edu/journeys/01/aug01/feature_full_page_1.html}.
(3) The high tide was at ... am [... m] and the low tide was at ... pm [... m].
(4) Prior to construction, the bridge design was extensively studied to prevent any impact on the currents, fauna and whirlpools.
(5) The Ohnaruto bridge was designed to carry both cars and trains on the upper and lower decks respectively. The train link was never completed and the newer Akashi bridge does not carry trains. The bridge's lower deck carries today water between Awaji and Shikoku islands, and the tourist walkway.
(6) The Japanese website of uzu-no-michi is HERE. Viewing times are listed HERE and HERE. (The best times are highlighted in RED. The first column lists the flow or flood conditions (marée montante) and the second the ebb (jusant).)
(7) In Nature, turbulent vortices are usually developed with a relatively large initial size (macroscale), but they break down into smaller and smaller eddies in the process of turbulent mixing. In the smallest eddies (microscale), viscous resistance dissipates virtually all the kinetic energy that initially existed in the larger eddies. This process of vortex generation and dissipation is a key feature of turbulent flows. It is sometimes called a cascade of vortices from macro- to micro-scales.

Table 1 - Characteristics of large whirlpools


Strait :
Saltstraumen & Sandstraumen
Other name(s) :
Naruto kaikyo
Saltfjord & Skjerstadfjord
Corrievrekin, Charybdis
Country :
Location :
between Awaji and Shikoku islands
between Lofoten Pointand Vaerøy island, Lofoten islands
50 km North of Bodø
between Scarba and Jura islands, Western Scotland
Tidal range :
up to 1.7 m
up to 3 m (?)
Strait width :
1.3 km
8 km
? (Sandstraumen)
? (Saltstraumen)
Current speed :
up to over 9 knots (4.6 m/s)
up to 7 knots (3.6 m/s)
up to 9 knots (4.6 m/s)
Whirlpools :
Large whirlpools on the Southern end during ebb
Access :
Views from Ohnaruto bridge and from tourist boats
Two straits :  Sandstraumen & Saltstraumen
Views from the bridge crossing

Detailed photographs

Photo No. 1 : general view from Ohnaruto bridge.
Photo No. 2 : whirlpools and vortices with a freighter in background, note the large eddy (over 50-m diameter) on the right.
Photo No. 3 : tourist boat in the middle of the whirlpools.
Photo No. 4 : street of vortex.
Photo No. 5 : Freighter and whirlpools.
Photo No. 6 : whirlpool in foregound right with stranded freighter in background.
Photo No. 7 : freighter trapped in Naruto whirlpools which became grounded beneath the bridge.
Photo No. 8 : grounded bow of the freighter.
Photo No. 9 : grounded freighter on 17 Oct. 2001.
Photo No. 10 : Flood flow on 9 July 2002 beneath the bridge (Courtesy of Drs ICHIMIYA and BROWN).
Photo No. 11: Turbulent vortices during the flood flow on 9 July 2002 (Courtesy of Drs ICHIMIYA and BROWN).

Related links

{http://www.uq.edu.au/~e2hchans/photo.html#Whirlpools} Gallery of photographs
{http://www.smithsonianmag.si.edu/journeys/01/aug01/feature_full_page_1.html} "In the Eye of the Whirlpool", Smithsonian Journeys, Aug. 2001
{http://jin.jcic.or.jp/atlas/nature/nat12.html} Naruto Strait (1)
{http://www1.pref.tokushima.jp/english/sightseeing/whirlpools_e.html} Naruto Strait (2)
{http://www.maths.bris.ac.uk/~madhp/Whirlpools/} Whirlpools at Saltstraumen - Comments by Professor Howell PEREGRINE, Bristol University
{http://www.rs.noda.sut.ac.jp/~kaiyou/eddy.htm} Coherent oceanic structures
{http://www.math.uio.no/maelstrom/} Maelstrom


[1] VAN DYKE, M. (1982). "An Album of Fluid Motion." Parabolic Press, Stanford CA, USA, 176 pages.
[2] GJEVIK, G., MOE, H., and OMMUNDSEN, A. (1997). "Sources of the Maelstrom." Nature, Vol. 388, 28 Aug 1997, pp 837-838.
[3] NISHIMURA, T. (1986). ""The Tidal Whirlpools Encountered in the Naruto-Strait." K. Sanbunsha Publ., Tokyo, Japan, 145 pages.
[4] CHANSON, H. (2002). "Whirlpools. Experiencing Naruto Whirlpools." IAHR Newsletter, Vol. 40, No. 2, pp. 17 & 28-29.  (PDF file at UQeSpace) (Download PDF file)
[5] CHANSON, H. (1999). "The Hydraulics of Open Channel Flows : An Introduction." Butterworth-Heinemann, London, UK, 512 pages (ISBN 0 340 74067 1).


The writer acknowledges the help and support of Bernard CHANSON, Ms Y.H. CHOU and Prof. S. AOKI. He further acknowledges the assistance of Mr J. CHANSON, Dr T. NISHIMURA, Dr ICHIMIYA and Dr R. BROWN


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Hubert CHANSON is a Professor in Civil Engineering, Hydraulic Engineering and Environmental Fluid Mechanics at the University of Queeensland, Australia. His research interests include design of hydraulic structures, experimental investigations of two-phase flows, applied hydrodynamics, hydraulic engineering, water quality modelling, environmental fluid mechanics, estuarine processes and natural resources. He has been an active consultant for both governmental agencies and private organisations. His publication record includes over 620 international refereed papers and his work was cited over 3,700 times (WoS) to 5,600 times (Google Scholar) since 1990. Hubert Chanson is the author of several books : "Hydraulic Design of Stepped Cascades, Channels, Weirs and Spillways" (Pergamon, 1995), "Air Bubble Entrainment in Free-Surface Turbulent Shear Flows" (Academic Press, 1997), "The Hydraulics of Open Channel Flow : An Introduction" (Butterworth-Heinemann, 1st edition 1999, 2nd editon 2004), "The Hydraulics of Stepped Chutes and Spillways" (Balkema, 2001), "Environmental Hydraulics of Open Channel Flows" (Butterworth-Heinemann, 2004), "Applied Hydrodynamics: an Introduction of Ideal and Real Fluid Flows" (CRC Press, 2009), and "Tidal Bores, Aegir, Eagre, Mascaret, Pororoca: Theory And Observations" (World Scientific, 2011). He co-authored two further books "Fluid Mechanics for Ecologists" (IPC Press, 2002) and "Fluid Mechanics for Ecologists. Student Edition" (IPC, 2006). His textbook "The Hydraulics of Open Channel Flows : An Introduction" has already been translated into Spanish (McGraw-Hill Interamericana) and Chinese (Hydrology Bureau of Yellow River Conservancy Committee), and the second edition was published in 2004. In 2003, the IAHR presented him with the 13th Arthur Ippen Award for outstanding achievements in hydraulic engineering. The American Society of Civil Engineers, Environmental and Water Resources Institute (ASCE-EWRI) presented him with the 2004 award for the Best Practice paper in the Journal of Irrigation and Drainage Engineering ("Energy Dissipation and Air Entrainment in Stepped Storm Waterway" by Chanson and Toombes 2002). Hubert Chanson edited further several books : "Fluvial, Environmental and Coastal Developments in Hydraulic Engineering" (Mossa, Yasuda & Chanson 2004, Balkema), "Hydraulics. The Next Wave" (Chanson & Macintosh 2004, Engineers Australia), "Hydraulic Structures: a Challenge to Engineers and Researchers" (Matos & Chanson 2006, The University of Queensland), "Experiences and Challenges in Sewers: Measurements and Hydrodynamics" (Larrate & Chanson 2008, The University of Queensland), "Hydraulic Structures: Useful Water Harvesting Systems or Relics?" (Janssen & Chanson 2010, The University of Queensland), "Balance and Uncertainty: Water in a Changing World" (Valentine et al. 2011, Engineers Australia). He chaired the Organisation of the 34th IAHR World Congress held in Brisbane, Australia between 26 June and 1 July 2011.
 His Internet home page is http://www.uq.edu.au/~e2hchans. He also developed a gallery of photographs website {http://www.uq.edu.au/~e2hchans/photo.html} that received more than 2,000 hits per month since inception.

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