On integral length scales in anisotropic turbulence

Bewley, Gregory P.; Chang, Kelken; Bodenschatz, Eberhard

doi:10.1063/1.4726077

Cited by 32 publications

(27 citation statements)

References 25 publications

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“…The velocity scales are 6.4 ± 0.8 cm/s for the along component and 11.5 ± 0.3 cm/s for the across component. These values on the order of meters and centimeters are consistent with the small‐eddy limit in the inertial subrange and may apply despite evidence of anisotropy (Bewley et al, ; MacCready, ). Whether or not these scales relate to the eddies themselves is a question that remains unresolved.…”

Section: Discussionsupporting

confidence: 69%

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Surface Layer Turbulence Parameters Derived From 1‐s Wind Observations on the West Florida Shelf

2019

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One‐second wind data on the West Florida Shelf were used to examine turbulent scales from large eddies to small eddies in the atmospheric surface layer within a frequency band from 0.02 to 0.3 Hz (periods from ~1 min to ~3 s). Data were collected at two at‐sea locations spanning 6.5 months. Three events in three wind ranges were examined in exploring the one‐dimensional turbulent power spectra: >14 m/s, wind range I; those between 10 and 14 m/s, wind range II; and those between 5 and 10 m/s, wind range III. Events consisted of ensembles of abutting 30‐min subsets spanning 5.5 to 23 hr. The mean vector wind time scale of T0 = 30 min was found to be reasonable for the West Florida Shelf region. The first wind range provided the best results, more or less in line with a Kolmogorov −5/3 power law whose mean vector wind speed over 21 subsets (10.5 hr) was nearly 15 m/s. The one‐dimensional turbulent power spectra provided an estimate of the dissipation rate (ε) from which other turbulent quantities could be computed: u*, τ, and Cd (the frictional velocity, the surface stress, and the drag coefficient, respectively). The salient point here is that these quantities were larger than those from previous observational studies. Where the power law was not operant intrinsic turbulent spatial scales ranged from 1 to 0.1 m and provide evidence of anisotropy for frequencies greater than 0.1 Hz.

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Section: Discussionsupporting

confidence: 69%

“…Journal of Geophysical Research: Atmospheres the inertial subrange and may apply despite evidence of anisotropy (Bewley et al, 2012;MacCready, 1962). Whether or not these scales relate to the eddies themselves is a question that remains unresolved.…”

Section: Discussionmentioning

confidence: 99%

Surface Layer Turbulence Parameters Derived From 1‐s Wind Observations on the West Florida Shelf

2019

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“…Therefore the estimate of the Eulerian integral length scales is generally calculated as the distance at which the correlation function falls below a threshold value. For example Bewley et al (2012) assumed a value of 0.5 whereas Takimoto et al (2013) adopted 0.4. Note that this method may be problematic when computing scales associated to the ρ uu functions, since the extent of the iso-correlation lines corresponding to the threshold value may not be fully captured by the PIV field (see Fig.…”

Section: Integral Length and Time Scalesmentioning

confidence: 99%

Dispersion of a Passive Scalar Fluctuating Plume in a Turbulent Boundary Layer. Part I: Velocity and Concentration Measurements

Nironi

Salizzoni

Marro

et al. 2015

Boundary-Layer Meteorol

146

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The prediction of the probability density function (PDF) of a pollutant concentration within atmospheric flows is of primary importance in estimating the hazard related to accidental releases of toxic or flammable substances and their effects on human health. This need motivates studies devoted to the characterization of concentration statistics of pollutants dispersion in the lower atmosphere, and their dependence on the parameters controlling their emissions. As is known from previous experimental results, concentration fluctuations are significantly influenced by the diameter of the source and its elevation. In this study, we aim to further investigate the dependence of the dispersion process on the source configuration, including source size, elevation and emission velocity. To that end we study experimentally the influence of these parameters on the statistics of the concentration of a passive scalar, measured at several distances downwind of the source. We analyze the spatial distribution of the first four moments of the concentration PDFs, with a focus on the variance, its dissipation and production and its spectral density. The information provided by the dataset, completed by estimates of the intermittency factors, allow us to discuss the role of the main mechanisms controlling the scalar dispersion and their link to the form of the PDF. The latter is shown to be very well approximated by a Gamma distribution, irrespective of the emission conditions and the distance from the source. Concentration measurements are complemented by a detailed description of the velocity statistics, including direct estimates of the Eulerian integral length scales from two-point correlations, a measurement that has been rarely presented to date.

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“…Kundu, 1990, p. 424;Bewley et al, 2012) L ¼ A reasonable estimate can be obtained by scanning DO concentrations at a rate faster than the characteristic travel time.…”

Section: Dissolved Oxygen Balancementioning

confidence: 99%

“…From this data, a convenient measure of the extent of the region over which DO concentrations are appreciably correlated can be estimated by the integral length scale (e.g. Kundu, 1990, p. 424;Bewley et al, 2012) L ¼…”

Section: Dissolved Oxygen Balancementioning

confidence: 99%

Estimating and scaling stream ecosystem metabolism along channels with heterogeneous substrate

et al. 2013

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Measured diurnal curves of dissolved oxygen (DO) concentration have been used to estimate the gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NP) of aquatic communities. Open-system one-station and twostation methods have been employed to estimate the rate of NP, R, and GPP. We conducted field measurements in Minnehaha Creek, MN (44 o 56'N, 93 o 28'W), to quantify the spatial and temporal variabilities of DO concentrations and, consequently, evaluated the estimates of NP. Dimensionless analysis of DO mass balance revealed the dominance of local photosynthesis over respiration, advection, re-aeration, and dispersion along the studied reach. Two alternative estimation methods of stream metabolism provided similar estimates of NP with 0.65 > k a T a > 0.17 within the studied reach where k a is the re-aeration rate and T a is the water parcel average travel time. The spatial variability of DO change along the creek revealed an average length scale of 10 m over which DO exhibited significant autocorrelation. The autotrophic-heterotrophic balance, quantified by GPP to R ratio, scaled with local stream geomorphic and hydraulic conditions from diverse geographic areas, providing useful predictive relationships expressed in terms of easily measurable abiotic parameters.

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On integral length scales in anisotropic turbulence

Cited by 32 publications

References 25 publications

Surface Layer Turbulence Parameters Derived From 1‐s Wind Observations on the West Florida Shelf

Surface Layer Turbulence Parameters Derived From 1‐s Wind Observations on the West Florida Shelf

Dispersion of a Passive Scalar Fluctuating Plume in a Turbulent Boundary Layer. Part I: Velocity and Concentration Measurements

Estimating and scaling stream ecosystem metabolism along channels with heterogeneous substrate

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