What describes the motion of fluid swirling rapidly around a center in fluid dynamics?

The motion of fluid swirling rapidly around a center is described as a vortex. In fluid dynamics, a vortex is characterized by a rotational motion where fluid elements circulate around an axis. This phenomenon can occur in various scenarios, such as in tornadoes, whirlpools, or around blades of a propeller, where the fluid adheres to the rotation and movement patterns created by surrounding forces.

In contrast, advection refers to the transport of a substance or property by bulk motion of the fluid itself, typically in the context of heat or mass transfer. Convection describes the process where heat is transferred through a fluid due to the movement of the fluid itself, encompassing both conduction and advection mechanisms. Diffusion involves the gradual spreading of particles from areas of higher concentration to areas of lower concentration, driven primarily by random thermal motion.

While all these terms relate to fluid motion or transport processes, the specific characteristic of rapid swirling around a center distinctly identifies a vortex, making it the correct description in this context.