Vortex
In fluid dynamics, a
vortex is a region within a fluid where the flow is mostly a spinning motion about an imaginary axis, straight or curved. That motion pattern is called a
vortical flow. Vortices form in stirred fluids, including liquids, gases, and plasmas. Some common examples are smoke rings, the whirlpools often seen in the wake of boats and paddles, and the winds surrounding hurricanes, tornadoes and dust devils. Vortices form in the wake of airplanes and are prominent features of Jupiter's atmosphere. Vortices are a major component of turbulent flow. In the absence of external forces, viscous friction within the fluid tends to organize the flow into a collection of so-called
irrotational vortices. Within such a vortex, the fluid's velocity is greatest next to the imaginary axis, and decreases in inverse proportion to the distance from it. The vorticity is very high in a core region surrounding the axis, and nearly zero in the rest of the vortex; while the pressure drops sharply as one approaches that region. Once formed, vortices can move, stretch, twist, and interact in complex ways.