WHIRLPOOL Abstract. Whirlpools are most familiar as vortices in the fast-fluid flow of rivers, usually in the form of an eddy downstream of some obstruction. Whirlpools can also occur in certain marine conditions, usually near particular coasts. Keywords: Fluid vortices, water, river flow A whirlpool, whether in water or other liquid, is a rotary current or vortex produced by the interaction of opposing currents in the fluid or surface winds over it. In rivers they form as eddies downstream of obstacles like jetties and bridge piers, the more readily when conditions are turbulent. Whirlpools are less common in seas and oceans but can develop from the interaction of opposing tidal flows especially where coastal and bottom configurations offer narrow, deep passages of considerable depth. Whirlpools are also created in the turbulent flow at the base of cascades or waterfalls as at Niagara. In the vortex of the whirlpool, the dynamic flow is a spiralling motion downwards. A return of water to the surface takes place in the manner of a quasi-stationary rising current known as a kolk or boil. This is visible at the surface as a heaving disturbance of the fluid. The severest sea-whirlpools are those of Corryvreckan off Western Scotland, Moskstraumen in the Lofoten Islands, Norway, and the Old Sow between Maine and New Brunswick. Other major whirlpools include Naruto between Tokushima and Awaji Island in Hyogo (Japan), Saltstraumen (Norway), and Garofalo (Italy). When their power is intense, the term maelstrom is often used. The often-cited sea-whirlpool Charybdis is a fiction, being no more than rough choppy water arising from wind blowing obliquely across fast-moving tidal water flowing steadily in one direction, or in the opposite direction when the tide is ebbing. G. TERENCE MEADEN Tornado and Storm Research Organisation, Oxford Published by Wiley Water On-line 2005