Feeding of Plankton in a Turbulent Environment: A Comparison of Analytical and Observational Results Covering Also Strong Turbulence

Pécseli, H. L.; Trulsen, J.; Stiansen, Jan Erik; Sundby, Svein

doi:10.3390/fluids5010037

Cited by 3 publications

(12 citation statements)

References 66 publications

(158 reference statements)

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“…shown on a double logarithmic scale for varying normalized separation r/η K , with η K = (ν 3 / ) 1/4 being the Kolmogorov length scale (see also Pécseli et al 2020). The Kolmogorov velocity u K = (ν ) 1/4 is used for normalization.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Table 2. The specific energy dissipation (dissipated energy per unit mass of fluid) and other characteristic turbulence parameters as found in the oceans (Granata & Dickey 1991;Kiørboe & Saiz 1995;Pécseli et al 2020).…”

Section: Basic Resultsmentioning

confidence: 99%

“…A key parameter for characterizing turbulence conditions is the specific energy dissipation rate . This is used in many applications, for instance for quantifying the turbulent mixing in marine environments (Kiørboe 2008;Pécseli et al 2020). When an estimate for the wavenumber velocity power spectrum is obtained, can be estimated (Stiansen & Sundby 2001) by comparing experimental results with the Kolmogorov-Obukhov spectrum C 0 2/3 k −5/3 , where C 0 ∈ {0.4 − 0.9} is the Kolmogorov-Obukhov constant (Sreenivasan 1995).…”

Section: Estimation Of the Specific Energy Dissipation Ratementioning

confidence: 99%

“…In many experiments, in the laboratory or in nature, the velocity V can be chosen freely, at least to some extent. In a number of cases, however, the velocity is imposed by external conditions, such as a tidal current (Pécseli et al 2020). A practical advantage of using Taylor's hypothesis is that a one-point measurement suffices.…”

Section: Estimation Of the Specific Energy Dissipation Ratementioning

confidence: 99%

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On the applicability of Taylor's hypothesis, including small sampling velocities

Pécseli

Trulsen

2021

J. Fluid Mech.

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Taylor's hypothesis, or the frozen turbulence approximation, can be used to estimate also the specific energy dissipation rate $\epsilon$ by comparing experimental results with the Kolmogorov–Obukhov expression. The hypothesis assumes that a frequency detected by an instrument moving with a constant large velocity $V$ can be related to a wavenumber by $\omega = k V$ . It is, however, not obvious how large the translational velocity has to be in order to make the hypothesis valid, or at least applicable with some acceptable uncertainty. Using the space–time-varying structure function for homogeneous and isotropic conditions, this question is addressed in the present study with emphasis on small velocities $V$ . The structure function is obtained using results from numerical solutions of the Navier–Stokes equation. Particular attention is given to the $V$ variation of the estimated specific energy dissipation, $\epsilon _{est}$ , compared with the actual value, $\epsilon$ , used in the numerical calculations. In contrast to previous studies, the results emphasize velocities $V$ less than or comparable to the one-component root-mean-square velocity, $u_{rms}$ . We find that $\epsilon$ can be determined to an acceptable accuracy for $V \geq 0.3\,u_{rms}$ . A simple analytical model is suggested to explain the main features of the observations, both Eulerian and Lagrangian. The model assumes that the observed time variations are solely due to eddies moving past the observer, thus ignoring eddy deformation and intermittency effects. In spite of these simplifications, the analysis accounts for most of the numerical results when also eddy-size-dependent velocities are accounted for.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Basic Resultsmentioning

confidence: 99%

Section: Estimation Of the Specific Energy Dissipation Ratementioning

confidence: 99%

Section: Estimation Of the Specific Energy Dissipation Ratementioning

confidence: 99%

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On the applicability of Taylor's hypothesis, including small sampling velocities

Pécseli

Trulsen

2021

J. Fluid Mech.

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“…Hidden mechanisms in scale and flow fields may hinder the detection by copepods. Pécseli et al [11] studied the encounter rate and the capture probabilities between cod larvae and prey (copepod) based on a field study under the different conditions of turbulence intensity.…”

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confidence: 99%