Vortex tubes in velocity fields of laboratory isotropic turbulence

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The streamwise and transverse velocities are measured simultaneously in isotropic grid turbulence at relatively high Reynolds numbers, Re λ ≃ 110-330. Using a conditional averaging technique, we extract typical intermittency patterns, which are consistent with velocity profiles of a model for a vortex tube, i.e., Burgers vortex. The radii of the vortex tubes are several of the Kolmogorov length regardless of the Reynolds number. Using the distribution of an interval between successive enhancements of a small-scale velocity increment, we study the spatial distribution of vortex tubes. The vortex tubes tend to cluster together. This tendency is increasingly significant with the Reynolds number. Using statistics of velocity increments, we also study the energetical importance of vortex tubes as a function of the scale. The vortex tubes are important over the background flow at small scales especially below the Taylor microscale. At a fixed scale, the importance is increasingly significant with the Reynolds number.

Section: Introductionmentioning

confidence: 50%

Vortex tubes in velocity fields of laboratory isotropic turbulence: Dependence on the Reynolds number

Mouri¹,

Hori²,

Kawashima³

2003

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“…While the radius R 0 is several times the Kolmogorov length η, the circulation velocity V 0 is about a half of the root-meansquare velocity fluctuation v 2 1/2 or several times the Kolmogorov velocity u K [4,9,10,11,14,15,17,18,19]. The observed v profile is close to the profile of a Burgers vortex [11,18,19]. We thus confirm the existence of vortex tubes and their responsibility for small-scale intermittency at high microscale Reynolds numbers.…”

Section: Velocity Profile Of Vortex Tubesmentioning

confidence: 99%

“…There are several possible configurations for laboratory experiments. Although the most popular configuration is isotropic grid turbulence, its Reynolds number is not high [18]. We instead use rough-wall boundary-layer tur- * Electronic address: hmouri@mri-jma.go.jp † Also at Meteorological and Environmental Service, Inc., Tama, Tokyo 206-0012, Japan.…”

Section: Introductionmentioning

confidence: 99%

Vortex tubes in turbulence velocity fields at Reynolds numbersReλ≃300–1300

Mouri¹,

Hori²,

Kawashima³

2004

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The most elementary structures of turbulence, i.e., vortex tubes, are studied using velocity data obtained in a laboratory experiment for boundary layers with Reynolds numbers Re(lambda) =295-1258 . We conduct conditional averaging for enhancements of a small-scale velocity increment and obtain the typical velocity profile for vortex tubes. Their radii are of the order of the Kolmogorov length. Their circulation velocities are of the order of the root-mean-square velocity fluctuation. We also obtain the distribution of the interval between successive enhancements of the velocity increment as the measure of the spatial distribution of vortex tubes. They tend to cluster together below about the integral length and more significantly below about the Taylor microscale. These properties are independent of the Reynolds number and are hence expected to be universal.

“…(6), the radius r x of a tube observed along the streamwise direction is different from its true radius r 0 as r x ≃ r 0 /(1 −sin 2 θ cos Hereafter we analyze data obtained in a wind tunnel [8]. Its test section was 3 × 2 × 18 m in size.…”

mentioning

confidence: 99%

Wavelet analysis of vortex tubes in experimental turbulence

Mouri

Takaoka

2002

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This report proposes a new method to study vortex tubes in one-dimensional velocity data of experimental turbulence. Vortex tubes are detected as local maxima on the scale-space plot of wavelet transforms of the velocity data.Then it is possible to extract a typical velocity pattern. The result for data obtained in a wind tunnel is consistent with those of three-dimensional direct numerical simulations.