A two-dimensional example of these features subject to the constraint “omega equals k-squared psi” is the Lamb–Chaplygin dipole. Motion near “lines” of these features is described by three theorems devised by Helmholtz, which are proven using a theorem named for Kelvin. The Strouhal number is defined by the rate of “shedding” of these features, which generate a “street” named for von Karman. A set of three of these features that form a characteristic horseshoe shape surround an aircraft wing. A quantity named for these features is defined as the curl of flow velocity, whose surface integral is circulation. Small examples of these features are called eddies. For 10 points, name these swirling features in a fluid flow exemplified by tornadoes and whirlpools. ■END■
ANSWER: vortex [or vortices; accept vorticity; accept vortex shedding or von Karman vortex street or horseshoe vortex; accept eddies until read; prompt on specific types of vortices such as whirlpools]
<Physics>
= Average correct buzz position