Measurements of intermittency of turbulent motion in a boundary layer

Sandborn, V. A.

doi:10.1017/s0022112059000581

Cited by 53 publications

(18 citation statements)

References 2 publications

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“…Even though there is a systematic flow pattern in the fluid wake behind an obstacle, at high Reynolds numbers the flows can be highly fluctuating in time [e.g., Humphreys, 1960;Bearman, 1969], intermittent in time [e.g., Batchelor and Townsend, 1949;Sandborn, 1959], and spatially irregular [e.g., Cebeci and Smith, 1974, Figure 1.7; Faber, 1995, Figure 7 Figure 6], the turbulence is anisotropic, with the velocity fluctuations normal to the boundary having a lesser magnitude than the velocity fluctuations parallel to the boundary; far from the boundary the velocty fluctuations become quasi-isotropic. Note that the vy flow statistics largely excludes bursty bulk flows.…”

Section: Discussion: the Plasma Sheet As A Wakementioning

confidence: 99%

The driving of the plasma sheet by the solar wind

Borovsky¹,

Thomsen²,

Elphic³

1998

J. Geophys. Res.

341

386

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Abstract. The coupling of the plasma sheet to the solar wind is studied statistically using measurements from various satellite pairs: one satellite in the solar wind and one in either the magnetotail central plasma sheet or the near-Earth plasma sheet. It is found that the properties of the plasma sheet are highly correlated with the properties of the solar wind: specifically that (1) the density of the plasma sheet is strongly correlated with the density of the solar wind, (2) the temperature of the plasma sheet is strongly correlated with the velocity of the solar wind, (3) the particle pressure and total pressure of the plasma sheet are strongly correlated with the ram pressure of the solar wind, (4) By in the plasma sheet is strongly correlated with the By in the solar wind, (5) B•. in the plasma sheet is weakly correlated with the B•. in the solar wind, (6) Ey in the plasma sheet is weakly correlated with the Ey in the solar wind, and (7) plasma sheet earthwardtailward flow velocity is weakly anticorrelated with the solar wind velocity. After removing these solar wind dependencies, the dependencies of the properties of the plasma sheet on geomagnetic activity are reduced and changed. The time lags between the solar wind density and the plasma sheet density are investigated statistically and on a case-by-case basis; it is found that solar wind material reaches the midtail plasma sheet in --2 hours, reaches the near-Earth nightside plasma sheet in --4 hours, and reaches the dayside plasma sheet in --15 hours. The pathway for mass transport into the plasma sheet is explored; it is suggested that solar wind material is transported rapidly up the tail to the near-Earth region via the plasma sheet boundary layer, followed by poloidal transport via E x B convection in the near-Earth (low/•) plasma sheet or followed by eddy diffusion in the not-too-distant (high/•) plasma sheet. Analogies are drawn between the high Reynolds number plasma sheet and a high Reynolds number fluid wake.

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Section: Discussion: the Plasma Sheet As A Wakementioning

confidence: 99%

The driving of the plasma sheet by the solar wind

Borovsky¹,

Thomsen²,

Elphic³

1998

J. Geophys. Res.

341

386

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“…Here we define intermittency as a departure from Gaussianity, which is reflected by increasing flatness when scale decreases. Sandborn [37] introduced this definition in the context of boundary layer flows and for a historical overview on intermittency we refer to [38]. Alternative definitions of intermittency can be found, e.g., in [24], for example a steepening of the energy spectrum proposed by Kolmogorov in 1962 [26].…”

Section: Wavelet-based Statistical Diagnosticsmentioning

confidence: 99%

Wavelet transforms and their applications to MHD and plasma turbulence: a review

Farge

Schneider

2015

J. Plasma Phys.

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International audienceWavelet analysis and compression tools are reviewed and different applications to study MHD and plasma turbulence are presented. We introduce the continuous and the orthogonal wavelet transform and detail several statistical diagnostics based on the wavelet coefficients. We then show how to extract coherent structures out of fully developed turbulent flows using wavelet-based denoising. Finally some multiscale numerical simulation schemes using wavelets are described. Several examples for analyzing, compressing and computing one, two and three dimensional turbulent MHD or plasma flows are presented

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“…In turbulent pipe flow, the turbulence is everywhere, whereas near the edge of the boundary layer the flow is intermittently turbulent, i.e., the turbulent eddies are sharply separated from the nonturbulent fluid that is entrained from outside the boundary layer. A velocity-measuring probe, such as a hot wire held at a fixed distance from the wall, will therefore sometimes see a turbulent signal and sometimes a calm flow Sandborn, 1959). The calm flow is more likely at a velocity closer to the free-stream velocity because, owing to the lack of turbulence, there is no strong shear coupUng between adjacent strata and the entrained fluid does not feel the presence of the boundary.…”

Section: Velocity Distribution Near the Groundmentioning

confidence: 99%

Aerodynamic Characteristics of Atmospheric Boundary Layers.

Plate¹

1971

180

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Measurements of intermittency of turbulent motion in a boundary layer

Cited by 53 publications

References 2 publications

The driving of the plasma sheet by the solar wind

The driving of the plasma sheet by the solar wind

Wavelet transforms and their applications to MHD and plasma turbulence: a review

Aerodynamic Characteristics of Atmospheric Boundary Layers.

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