Analysis of velocity fluctuations and their intermittency properties in the surf zone using empirical mode decomposition

Schmitt, François G; Huang, Yongxiang; Lu, Zhiming; Liu, Yulu; Fernandez, N.

doi:10.1016/j.jmarsys.2008.11.012

Cited by 44 publications

(26 citation statements)

References 42 publications

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“…Several theoretical models have been put forward to describe the intermittent property of the energy dissipation field, for instance, the lognormal model [13], log-Poisson model [14,15], log-stable model [16,17], to list a few. Multifractality has also been recognized as a common feature of complex dynamic systems, such as financial activities [18][19][20], wind energy [21], geosciences [22,23], to name a few.…”

Section: Introductionmentioning

confidence: 99%

Intermittency measurement in two-dimensional bacterial turbulence

et al. 2016

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In this paper, an experimental velocity database of a bacterial collective motion , e.g., B. subtilis, in turbulent phase with volume filling fraction 84% provided by Professor Goldstein at the Cambridge University UK, was analyzed to emphasize the scaling behavior of this active turbulence system. This was accomplished by performing a Hilbert-based methodology analysis to retrieve the scaling property without the β−limitation. A dual-power-law behavior separated by the viscosity scale ℓ ν was observed for the qth-order Hilbert moment L q (k). This dual-power-law belongs to an inverse-cascade since the scaling range is above the injection scale R, e.g., the bacterial body length.The measured scaling exponents ζ(q) of both the small-scale (resp. k > k ν ) and large-scale (resp. k < k ν ) motions are convex, showing the multifractality. A lognormal formula was put forward to characterize the multifractal intensity. The measured intermittency parameters are µ S = 0.26 and µ L = 0.17 respectively for the small-and large-scale motions. It implies that the former cascade is more intermittent than the latter one, which is also confirmed by the corresponding singularity spectrum f (α) vs α. Comparison with the conventional two-dimensional Ekman-Navier-Stokes equation, a continuum model indicates that the origin of the multifractality could be a result of some additional nonlinear interaction terms, which deservers a more careful investigation. *

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Section: Introductionmentioning

confidence: 99%

Intermittency measurement in two-dimensional bacterial turbulence

et al. 2016

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“…At the low-frequency scale there is a typical Kolmogorov −5/3 slope and at high frequency a scaling regime with a 0.6 slope. For high frequencies there is a hump-like structure, which can be identified as the high energy associated with surf zone wave breaking (Schmitt et al, 2009). …”

Section: Psd Slope (ξ )mentioning

confidence: 99%

“…Such variability is often associated with turbulence, and multi-scaling properties of oceanic fields have been reported and studied in many previous studies: sea state (Kerman, 1993); phytoplankton concentration (Seuront et al, 1996a(Seuront et al, , b, 1999Lovejoy et al, 2001a); rainfall and cloud radiance (Tessier et al, 1993;Lovejoy and Schertzer, 2006); and satellite images of ocean colour, chlorophyll a and sea surface temperature (Lovejoy et al, 2001b;Nieves et al, 2007;Pottier et al, 2008;Turiel et al, 2009;de Montera et al, 2011;Renosh et al, 2015). Here we focus on coastal waters and consider particles transported by oceanic currents in this highly energetic medium (Svendsen, 1987;Schmitt et al, 2009). The solid phases in the environment have been described by hyperbolic particle size distribution (PSD) of clay aggregates in water (Amal et al, 1990), biological aggregate and marine snow (Jiang and Logan, 1991;Logan and Wilkinson, 1991), aerosol agglomerates (Wu and Friedlander, 1993) and flocs produced in the water, and wastewater discharge (Li and Ganczarczyk, 1989).…”

Section: Introductionmentioning

confidence: 97%

Intermittent particle dynamics in marine coastal waters

Renosh

Schmitt

Loisel

2015

Nonlin. Processes Geophys.

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Abstract. Marine coastal processes are highly variable over different space scales and timescales. In this paper we analyse the intermittency properties of particle size distribution (PSD) recorded every second using a LISST instrument (Laser In-Situ Scattering and Transmissometry). The particle concentrations have been recorded over 32 size classes from 2.5 to 500 µm, at 1 Hz resolution. Such information is used to estimate at each time step the hyperbolic slope of the particle size distribution, and to consider its dynamics. Shannon entropy, as an indicator of the randomness, is estimated at each time step and its dynamics is analysed. Furthermore, particles are separated into four classes according to their size, and the intermittent properties of these classes are considered. The empirical mode decomposition (EMD) is used, associated with arbitrary-order Hilbert spectral analysis (AHSA), in order to retrieve scaling multifractal moment functions, for scales from 10 s to 8 min. The intermittent properties of two other indicators of particle concentration are also considered in the same range of scales: the total volume concentration C vol-total and the particulate beam attenuation coefficient c p (670). Both show quite similar intermittent dynamics and are characterised by the same exponents. Globally we find here negative Hurst exponents (meaning the small scales show larger fluctuation than large scales) for each time series considered, and nonlinear moment functions.

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“…Since surface waves often occupy the same frequency range as marine turbulence, it is difficult to separate the latter from waveinduced velocity fluctuations using simple filtration. Therefore, development of various techniques and methods capable to remove the bias produced by surface waves from ADCP measurements of turbulent shear stress was an important issue over the past decade (Shaw and Trowbridge, 2001;Trowbridge and Elgar, 2003;Whipple et al, 2006;Feddersen and Williams, 2007;Rosman et al, 2008;Schmitt et al, 2009;Huang et al, 2010;Kirincich et al, 2010). This paper addresses two challenges.…”

Section: K a Korotenko Et Al: Effect Of Variable Winds On Current mentioning

confidence: 99%

Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

2012

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Abstract. Wind and wave effects on tidal current structure and turbulence throughout the water column are examined using an upward-looking acoustic Doppler current profiler (ADCP). The instrument has been deployed on the seafloor of 18-m mean depth, off the north-eastern French coast in the eastern English Channel, over 12 tidal cycles, and covered the period of the transition from mean spring to neap tide, and forcing regimes varied from calm to moderate storm conditions. During storms, we observed gusty winds with magnitudes reaching 15 m s −1 and wave heights reaching up to 1.3 m. Analysis of velocity spectra revealed a noticeable contribution of wind-induced waves to spectral structure of velocity fluctuations within the subsurface layer. Near the surface, stormy winds and waves produced a significant intensification of velocity fluctuations, particularly when the sustained wind blew against the ebb tide flow. As during wavy periods, the variance-derived Reynolds stress estimates might include a wave-induced contamination, we applied the Variance Fit method to obtain unbiased stresses and other turbulent quantities. Over calm periods, the turbulent quantities usually decreased with height above the seabed. The stresses were found to vary regularly with the predominantly semidiurnal tidal flow. The along-shore stress being generally greater during the flood flow (∼ 2.7 Pa) than during the ebb flow (∼ −0.6 Pa). The turbulent kinetic energy production rate, P , and eddy viscosity, A z , followed a nearly regular cycle with close to a quarter-diurnal period. As for the stresses, near the seabed, we found the maximum values of estimated quantities of P and A z to be 0.1 Wm −3 and 0.5 m 2 s −1 , respectively, during the flood flow. Over the storm periods, we found the highest unbiased stress values (∼ −2.6 Pa) during ebb when tidal currents were opposite to the southwesterly winds while, during the flood, the surface stresses slightly exceeded those estimated for a calm period. A comparison of obtained results gives a good agreement with those of other researchers working on direct measurements of turbulence in tidal flows.

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Analysis of velocity fluctuations and their intermittency properties in the surf zone using empirical mode decomposition

Cited by 44 publications

References 42 publications

Intermittency measurement in two-dimensional bacterial turbulence

Intermittency measurement in two-dimensional bacterial turbulence

Intermittent particle dynamics in marine coastal waters

Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

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