Discrete shedding modes in the von Kármán vortex street

In the laminar vortex street behind a circular cylinder, only few distinct shedding modes for a large range of aspect ratios and various end conditions are observed. The nth mode is characterized by a Strouhal number Stn and a shedding angle, θn, both of which vary continuously with the Reynolds number. The experimentally observed discontinuities in the Strouhal–Reynolds number relationship are transitions between these shedding modes.