swirl

Swirl refers to a motion or pattern in which matter or imagery moves with a twisting, spiraling motion around a central axis. It can describe physical movement in fluids, weather systems, as well as decorative or symbolic patterns.

In physics and fluid dynamics, a swirl arises when a fluid possesses angular momentum around an axis, creating vortices or eddies. Real-world examples include whirlpools, smoke rings, tornadoes, and the spiraling of a stirred liquid. The intensity of a swirl in a flow is often described using the swirl number, a dimensionless quantity that compares axial to tangential momentum.

Engineering uses of swirl include enhancing mixing and combustion. Swirl injectors and swirl burners use rotational flow to improve fuel-air mixing and stability in gas turbines and reactors.

Natural phenomena: Swirling patterns appear in cloud formations, rivers, and plant patterns. In meteorology, large-scale vortices such as cyclones show swirling motion around a low-pressure center.

Cultural and design contexts: Swirl is a common motif in art, architecture, typography, and decorative patterns. In food and beverage, "swirl" describes a pattern created by combining two or more components, for example chocolate swirl in ice cream or coffee.

See also: vortex, spiral, eddy, whirlpool, turbulence.