Vortex

A region of fluid in which motion revolves around an axis. Its rotation may be organized around a recognizable core or distributed across a broader flow.

Vorticity: A measure of the local rotation of a fluid, defined as the curl of its velocity field. It quantifies the rotation concentrated within a vortex.
Streamline: A curve tangent everywhere to the instantaneous velocity of a fluid. Streamlines reveal how fluid paths curve around a vortex.
Smoke ring: A toroidal vortex made visible by smoke or another suspended tracer. Its closed, traveling ring makes vortex structure visible in air.
Kármán vortex street: A repeating pattern of vortices shed alternately from opposite sides of a bluff body in a flow. Alternating vortex shedding can create oscillating forces on structures.
Fluid dynamics: The study of how liquids and gases move and exert forces. Vortices are recurring structures within fluid motion.
Circulation: The line integral of a velocity field around a closed curve in a fluid. Circulation measures the net swirling motion enclosed by a loop around the vortex.
Potential flow: An idealized flow whose velocity is the gradient of a scalar potential and whose vorticity is zero. It describes irrotational regions around some vortices, despite rotation concentrated at a core.
Tornado: A violently rotating column of air extending from a thunderstorm to the ground. It is a powerful atmospheric vortex with a narrow, often visible core.
Magnus effect: A force on a spinning body moving through a fluid, produced by differences in flow and pressure around it. The body's rotation changes the surrounding flow and creates lift.
Turbulence: Irregular fluid motion characterized by fluctuating velocities and interacting scales. Turbulent flows contain vortices that stretch, tilt, and interact.

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