(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.
Definition source: National Oceanic and Atmospheric Administration
