A vortex is a vortex or point where the water or other liquid moves downward in a circular or spiral motion, with a funnel-shaped depression in the middle . In North German, a vortex with a strong countercurrent is also called a neer.
Of particular interest are the eddies that form in the upper courses of the rivers as a result of the unevenness of the bottom combined with waterfalls and rapids . Their erosion effect is characterized by the formation of whirlpool holes or giant pots . At mouths of water into the sea, eddies can arise from the interaction of fresh water with salt water , since salt water is heavier than fresh water. Furthermore, vortices can arise from inflows and outflows below the water surface (in deep water ), for example through suction pipes for cooling water (fresh water) from power plants.
Whirlpools can be particularly dangerous for bathers and boats , but hardly for larger ships . The circular or spiral movement of the water pulls the swimmer or boat with it and pulls it to the bottom. It is very difficult to resist the swirling motion of a vortex. Therefore, there is a risk of drowning. For this reason, leading experts in the German Armed Forces advise not to fight against the vortex, but to dive towards the ground with all your strength and to submerge the vortex, as it were, because the suction effect is weakest at the bottom.
Examples in nature
Eddies arise in rapid currents, which are not at all in the open sea and seldom present in narrow seas. Examples of vortices in nature are:
- Corryvreckan: The dangerous whirlpool within the Corryvreckan Strait , also known as the Corryvreckan whirlpool , has already cost the lives of numerous ship crews, people and animals and is both a tourist attraction and a danger zone. It is located in the Scottish county of Argyll and Bute at the end of the Jura Sound , between the island of Jura and Scarba . It is considered to be the second strongest marine vortex in the world. For shipping, it is considered the only impassable place in the British Isles .
- Moskenesstraumen / Saltstraumen / Mahlstrom: This large vortex system off the Norwegian Lofoten , which is often summarized under the term "Mahlstrom", but correctly consists of the Moskenesstraumen and the Saltstraumen , is often the most dangerous due to its flow speed of 27.8 kilometers per hour The current of the world. In fact, it only poses a more serious hazard to smaller boats.
- Danube wave: This formerly very strong vortex below Grein in Upper Austria on the north side of the island of Wörth has lost its danger for shipping since 1866 due to explosions. Upstream in Regensburg is the Regensburger Strudel below the Stone Bridge . It results from the narrow bridge passages.
- Congo Pack: The Congo Pack is located in the Democratic Republic of the Congo in the Congo River . It's a little downstream from Vivi .
- Naruto whirlpools: The extremely strong Naruto whirlpools in a strait in Japan have speeds of up to 20 kilometers per hour.
- Old Sow: The Old Sow is a whirlpool between New Brunswick and Maine . It reaches top speeds of up to 27.7 kilometers per hour.
- Charybdis: The Charybdis from the Odyssey was said to be in the Strait of Messina between Sicily and mainland Italy.
Whirlpool in drains
There has been a long controversy over the question of whether the rotation behavior of a water vortex, for example in a bathtub, is decisively influenced by the Coriolis force . After the drain is opened, the resulting vortex would have to rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, similar to what happens in the atmosphere in high and low pressure areas. Under ideal conditions, this effect of the Coriolis force was proven in 1962 by Ascher Shapiro in water basins each two meters in diameter, with one series of tests taking place in Watertown (Massachusetts) , and a second with an identical structure shortly afterwards by other physicists in Cambridge , England. The water content of the pools had previously been brought to absolute calm. The direction of rotation of the vortex as it drained was always counter-clockwise. In 1965 the same experiment was carried out in Sydney . Here the vortex always turned clockwise. However, since the Coriolis force in water basins is extremely low, the phenomenon only works reliably under ideal conditions, if at all. That it can be observed in practice is refuted by other studies.
- Duden: Entry "Neer, die", accessed on July 31, 2018
- The dangers of bathing. (No longer available online.) Augsburger Allgemeine / DDP, July 26, 2010, archived from the original on November 23, 2010 ; Retrieved July 27, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- The great debate plughole. In: The Guardian , September 13, 2003 (accessed September 16, 2017)
- Ascher H. Shapiro: Bath-Tub Vortex . In: Nature . 196, No. 4859, 1962, doi : 10.1038 / 1961080b0 . , pp. 1080-1081.
- AM Binnie: Some Experiments on the Bath-Tub Vortex . In: Journal of Mechanical Engineering Science . 6, No. 3, 2006, doi : 10.1243 / JMES_JOUR_1964_006_037_02 . , pp. 256-257.
- Lloyd M. Trefethen, RW Bilger, PT Fink, RE Luxton, RI Tanner: The Bath-Tub Vortex in the Southern Hemisphere . In: Nature . 207, No. 5001, 1965, doi : 10.1038 / 2071084a0 . , pp. 1084-1085.
- Christoph Drösser: Right? Strange vortex. On: zeit.de. March 3, 2010, accessed December 14, 2014.
- Jearl Walker : The Flying Circus of Physics . Oldenbourg Wissenschaftsverlag, 2007, ISBN 978-3-486-58067-9 ( limited preview in Google book search).
- Norbert Lossau : Five minutes of physics: bathtubs and low pressure areas. In: The world . June 6, 2007.