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Visualisation of the Kármán vortex street in the wake behind a circular cylinder in air; the flow is made visible through release of oil vapour in the air near the cylinder. The wake is the region of disturbed flow (often turbulent) downstream of a solid body moving through a fluid, caused by the flow of the fluid around the body.
For the wake of a circular cylinder, for which the reference length is conventionally the diameter d of the circular cylinder, the lower limit of this range is Re ≈ 47. [9] [10] Eddies are shed continuously from each side of the circle boundary, forming rows of vortices in its wake. The alternation leads to the core of a vortex in one row ...
A vortex street around a cylinder. This can occur around cylinders and spheres, for any fluid, cylinder size and fluid speed, provided that the flow has a Reynolds number in the range ~40 to ~1000. [1] In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. [2]
Where is the dimensionless Strouhal number, is the vortex shedding frequency (Hz), is the diameter of the cylinder (m), and is the flow velocity (m/s). The Strouhal number depends on the Reynolds number R e {\displaystyle \mathrm {Re} } , [ 5 ] but a value of 0.22 is commonly used. [ 6 ]
In the dynamics of fluid, a vortex is fluid that revolves around the line of flow. This flow of fluid might be curved or straight. Vortices form from stirred fluids: they might be observed in smoke rings, whirlpools, in the wake of a boat or the winds around a tornado or dust devil.
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An engine cowling on a Southwest Airlines Boeing 737-800 fell off on Sunday during takeoff in Denver and struck the wing flap, prompting the Federal Aviation Administration to open an investigation.
Wake turbulence can occasionally, under the right conditions, be heard by ground observers. [25] On a still day, the wake turbulence from heavy jets on landing approach can be heard as a dull roar or whistle. This is the strong core of the vortex. If the aircraft produces a weaker vortex, the breakup will sound like tearing a piece of paper.