Vortex Street


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vortex street

[′vȯr‚teks ‚strēt]
(fluid mechanics)
A series of vortices which are systematically shed from the downstream side of a body around which fluid is flowing rapidly. Also known as vortex trail; vortex train.

Vortex Street

 

a system of sequential vortices that form in a fluid during flow around long cylindrical bodies whose axis is perpendicular to the direction of movement. The vortices break off alternately from the sides of the body, and they arrange themselves in checkerboard order in the form of two chains behind the body. The vortices of one chain rotate clockwise, and those of the other chain rotate counterclock-wise. Vortex streets are unstable and may be clearly ob-served only at small Reynolds numbers Re. In addition, a fixed ratio has been observed between the width h of a vortex street and the distance l between the adjacent vortices of each row: h/I = 0.281. Experiments have demonstrated that the size of the vortex street also depends on the size of the streamlined body.

Energy is expended in the formation of vortices; therefore the body behind which the vortex street originates experiences drag. The resistance of the body decreases with a de-crease in the width of the vortex street.

References in periodicals archive ?
This phenomenon coincides with what we know: decreasing d/D leads to the narrower wake and smaller vortices after the upstream cylinder [19]; before L/D reaches the critical value, the vortex street is suppressed between the two cylinders [30].
At d/D = 1 and L/D = 3, the vortex street is suppressed behind the upstream cylinder.
Using a muscle recording technique on Kirman gaiting fish that resembles acupuncture with long wires, I found that fish shut down almost all of their body muscles when positioned in the vortex street behind the cylinder.
I called this behavior "Karman gait," after Theodore von Karman, the famous fluid dynamicist who formally described the phenomenon of vortex streets.
This characteristic vortex pattern is known as the Karman vortex street, after the great Hungarian-born American aerodynamicist, Theodore von Karman.
Dramatic examples of the Karman vortex street can be seen in rivers downstream of the cylindrical columns supporting bridges.
Above: Von Karman Vortex Streets, Aleutian Islands, Alaska.