Kármán vortex street

Article By:

Bryson, Arthur E., Jr. Department of Aeronautics and Astronautics, Stanford University, Stanford, California.

Telionis, Demetri P. Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.362200

A double row of line vortices in a fluid. Under certain conditions, a Kármán street is shed in the wake of bluff cylindrical bodies when the relative fluid velocity is perpendicular to the generators of the cylinder (Fig. 1). This shedding of eddies occurs first from one side of the body and then from the other, an unusual phenomenon because the oncoming flow may be perfectly steady. Vortex streets can often be seen, for example, in rivers downstream of the columns supporting a bridge. The streets have been studied most completely for circular cylinders at low subsonic flow speeds. Regular, perfectly periodic vortex streets occur in the range of Reynolds number (Re) 50–300, based on cylinder diameter. Above a Reynolds number of 300, a degree of randomness begins to occur in the shedding due to secondary instabilities, which becomes progressively greater as Reynolds number increases, until finally the wake is completely turbulent. The highest Reynolds number at which some slight periodicity is still present in the turbulent wake is about 10⁶. See also: Reynolds number

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