Whirlpool

Key takeaways

Whirlpool belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Whirlpool to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Whirlpool from memory before moving on to harder problems.

Reference excerpt

A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. Miniature whirlpools form when a bath or a sink is draining. More powerful ones formed in seas or oceans may be called maelstroms ( MAYL-strom, -⁠strəm). Vortex is the proper term for a whirlpool that has a downdraft. In narrow ocean straits with fast flowing water, whirlpools are often caused by tides. Many stories tell of ships being sucked into a maelstrom, although only smaller craft are actually in danger. Small whirlpools appear at river rapids and can be observed downstream of artificial structures such as weirs and dams. Large cataracts, such as Niagara Falls, produce strong whirlpools.

Etymology

One of the earliest uses in English of the Scandinavian word malström or malstrøm was by Edgar Allan Poe in his short story "A Descent into the Maelström" (1841). The Nordic word itself is derived from the Dutch word maelstrom (pronounced [ˈmaːlstroːm] ; modern spelling maalstroom), from malen ('to mill' or 'to grind') and stroom ('stream'), to form the meaning 'grinding current' or literally 'mill-stream', in the sense of milling (grinding) grain.

Notable whirlpools

Saltstraumen

Saltstraumen is a narrow strait located close to the Arctic Circle, 33 km (20 mi) south-east of the city of Bodø, Norway. It has one of the strongest tidal currents in the world. Whirlpools up to 10 metres (33 ft) in diameter and 5 metres (16 ft) in depth are formed when the current is at its strongest.

Moskstraumen

Moskstraumen, or the Lofoten maelstrom, is an unusual system of tidal currents in the open seas near the Lofoten Islands off the Norwegian coast. It is the second strongest whirlpool in the world with flow currents reaching speeds as high as 32 km/h (20 mph). This is supposedly the whirlpool depicted in Olaus Magnus's map, labeled as "Horrenda Caribdis" (Charybdis). The Moskstraumen is formed by the combination of powerful semi-diurnal tides and the unusual shape of the seabed, with a shallow ridge between the Moskenesøya and Værøya islands which amplifies and whirls the tidal currents. The fictional depictions of the Moskstraumen by Edgar Allan Poe, Jules Verne, and Cixin Liu describe it as a gigantic circular vortex that reaches the bottom of the ocean, when in fact it is a set of currents and crosscurrents with a rate of 18 km/h (11 mph). Poe described this phenomenon in his short story "A Descent into the Maelström", which in 1841 was the first to use the word maelstrom in the English language; in this story related to the Lofoten Maelstrom, two fishermen are swallowed by the maelstrom while one survives.

Corryvreckan

The Corryvreckan is a narrow strait between the islands of Jura and Scarba, in Argyll and Bute, on the northern side of the Gulf of Corryvreckan, Scotland. It is the third-largest whirlpool in the world. Flood tides and inflow from the Firth of Lorne to the west can drive the waters of Corryvreckan to waves of more than 9 metres (30 ft), and the roar of the resulting maelstrom, which reaches speeds of 18 km/h (11 mph), can be heard 16 km (10 mi) away. Though it was classified initially as non-navigable by the Royal Navy it was later categorized as "extremely dangerous". A documentary team from Scottish independent producers Northlight Productions once threw a mannequin into the Corryvreckan ("the Hag") with a high-visibility vest and depth gauge. The mannequin was swallowed and spat up far down current with a depth gauge reading of 262 m (860 ft) and evidence of being dragged along the bottom for a great distance.

Niagara Whirlpool

About three miles (4.8 kilometers) downstream from Niagara Falls is the Niagara Whirlpool. Located mostly in Canada and partially in the United States, the whirlpool is crossed by the Whirlpool Aero Car. The basin of the whirlpool is 1,700 feet (518 meters) long and 1,200 feet (365 meters) wide. Its maximum water depth is 125 feet (38 meters).

Other notable maelstroms and whirlpools Old Sow whirlpool is located between Deer Island, New Brunswick, Canada, and Moose Island, Eastport, Maine, USA. It is given the epithet "pig-like" as it makes a screeching noise when the vortex is at its full fury and reaches speeds of as much as 27.6 km/h (17.1 mph). The smaller whirlpools around this Old Sow are known as "Piglets".

The Naruto whirlpools are located in the Naruto Strait near Awaji Island in Japan, which have speeds of 26 km/h (16 mph). Skookumchuck Narrows is a tidal rapids that develops whirlpools, on the Sunshine Coast, British Columbia, Canada with speeds of the current exceeding 30 km/h (19 mph). French Pass (Te Aumiti) is a narrow and treacherous stretch of water that separates D'Urville Island from the north end of the South Island of New Zealand. In 2000 a whirlpool there caught student divers, resulting in fatalities. A short-lived whirlpool sucked in a portion of the 1,300-acre (530 ha) Lake Peigneur in Louisiana, United States after a drilling mishap on November 20, 1980. This was not a naturally occurring whirlpool, but a disaster caused by underwater drillers breaking through the roof of a salt mine. The lake then drained into the mine until the mine filled and the water levels equalized, but the formerly 10-foot (3.0 m) deep lake was now 1,300 feet (400 m) deep. This mishap caused a sinkhole, and in the end, resulted in the destruction of five houses, the loss of nineteen barges and eight tug boats, oil rigs, a mobile home, trees, acres of land, and most of a botanical garden. The adjacent settlement of Jefferson Island was reduced in area by 10%. A crater 0.5 miles (0.8 km) across was left behind. Nine of the barges, which had sunk, later resurfaced after the whirlpool subsided. A more recent example of an artificial whirlpool that received significant media coverage occurred in early June 2015, when an intake vortex formed in Lake Texoma, on the Oklahoma–Texas border, near the floodgates of the dam that forms the lake. At the time of the whirlpool's formation, the lake was being drained after reaching its highest level ever. The Army Corps of Engineers, which operates the dam and lake, expected that the whirlpool would last until the lake reached normal seasonal levels by late July.

Dangers

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Whirlpool

Start with the simplest possible case. Write down what Whirlpool claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Whirlpool before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Whirlpool ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Whirlpool

In research: Whirlpool appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Whirlpool in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Whirlpool is common in secondary-school and first-year university syllabi. It links to neighbouring topics Natural hazards, Vortices, Whirlpools, so understanding it makes those chapters shorter.
In everyday life: Look for Whirlpool outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Whirlpool in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Whirlpool means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Whirlpool out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Whirlpool in simple terms?

A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. Miniature whirlpools form when a bath or a sink is draining.

Why does Whirlpool matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Whirlpool?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Whirlpool.