Kármán Vortex Streets

The phenomenon on the tubes in a tube row, which vibrate alternately along the row in the transverse and stream-wise directions, will be explained by a vortex model. This model consists of the symmetrical vortex pair trains behind the stream-wisely vibrating tubes, and the Karman vortex streets behind the transversely vibrating tubes. It will be shown in the paper that the coupling between these two groups of vortex systems can excite the tube arrays to perform this fluidelastic vibration. A criterion for the onset of this orbital movement will be given with the expression ξ = R/Sxt. This criterion predicts a strong fluidelastic vibration for tubes with low transverse tube spacings and low natural flexible frequencies in a high speed flow. The theory leading to this criterion is based on the phenomenon of the variation in the position of the separation point for the free shear layer during the cylinder vibration. A switching of the jet for maintaining the fluidelastic vibration is then a result of this variation.

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Lewis number effects on premixed flames interactioning with turbulent Karman vortex streets

Fuel and Energy Abstracts ◽

10.1016/0140-6701(95)80640-7 ◽

1995 ◽

Vol 36 (3) ◽

pp. 207

Keyword(s):

Premixed Flames ◽

Lewis Number ◽

Vortex Streets ◽

Karman Vortex

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Blockage and sheltering effects of vegetation in turbulent flow

10.5194/egusphere-egu2020-20999 ◽

2020 ◽

Author(s):

Wei-Jie Wang

Keyword(s):

Drag Coefficient ◽

Flow Resistance ◽

Aquatic Vegetation ◽

Reynolds Numbers ◽

Viscous Boundary Layer ◽

Vortex Streets ◽

Karman Vortex ◽

Viscous Boundary ◽

Sheltering Effect ◽

Blockage Effect

<p>The interaction between aquatic vegetation and water flow is investigated here focusing on the drag coefficient. Compared with the standard drag coefficient of isolated cylinder, the phenomena of "blockage effect" and "sheltering effect" are put forward for vegetation clusters with different vegetation densities and Reynolds numbers. "Blockage effect" occurs when the drag coefficient of vegetation cluster is greater than the standard drag coefficient of isolated cylinder. The reason is that viscous boundary layer attached to the surface of vegetation items, resulting that the effective flowing width between adjacent vegetation items is less than the spacing of them, which brings a greater flow resistance and the drag coefficient of vegetation array is greater than the standard drag coefficient. On the other trend, "sheltering effect" is formed when the drag coefficient of vegetation array is less than the standard drag coefficient. This effect usually occurs for flow with large Reynolds numbers. In this case, Karman vortex streets forms and these vortexes are filled in the vegetation interval, thus causing the drag coefficient of vegetation cluster to be less than the standard drag coefficient of isolated cylinder.</p>

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Atmospheric Refractivity Anomalies Induced by Mesoscale von Kármán Vortex Streets

Imaging and Applied Optics ◽

10.1364/pcdvt.2013.pw3f.2 ◽

2013 ◽

Author(s):

Christopher G. Nunalee ◽

Jean Minet ◽

Sukanta Basu ◽

Mikhail A. Vorontsov

Keyword(s):

Von Karman ◽

Vortex Streets ◽

Karman Vortex ◽

Von Kármán

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Static and dynamic calibrations of constant-temperature hot-wire systems

Journal of Fluid Mechanics ◽

10.1017/s0022112071001356 ◽

1971 ◽

Vol 47 (4) ◽

pp. 765-777 ◽

Cited By ~ 58

Author(s):

A. E. Perry ◽

G. L. Morrison

Keyword(s):

Constant Temperature ◽

Calibration Method ◽

Calibration Procedure ◽

Hot Wire ◽

Low Frequencies ◽

Conventional Procedure ◽

Vortex Streets ◽

Karman Vortex ◽

System Frequency ◽

Wire System

The conventional hot-wire static calibration procedure for the measurement of absolute turbulence intensities with constant-temperature hot-wire anemometers is investigated and serious errors are found. An alternative calibration procedure is developed which involves shaking the wire at low frequencies in a uniform flow. A series of tests indicate that this dynamic calibration method is more accurate and consistent than the conventional procedure.A method for verifying various calibration procedures is demonstrated. This method involves the measurement of velocity perturbations in a series of Karman vortex streets. The velocity perturbation amplitude is held fixed, but the frequency varies from one vortex street to another. This method also acts as a direct check of the hot-wire system frequency response.

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