(Also called Kármán vortex street, vortex trail, vortex train.) Two parallel rows of alternately placed vortices along the wake of an obstacle in a fluid of moderate Reynolds number.
Fluid drag can be calculated from the motion of these vortices, which are stable only for a certain ratio of the width of the street to the distance between vortices along the street.
See vortex cloud street.
Batchelor, G. K. 1967. An Introduction to Fluid Dynamics. Cambridge University Press, . pp. 261, 338, 536.