New insights into the fine-scale structure of turbulence

Wilczek, Michael

doi:10.1017/jfm.2015.536

Cited by 4 publications

(3 citation statements)

References 10 publications

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“…The majority of coherent structure identification methods used in fluid dynamics continues to be Eulerian (see, e.g., [4][5][6][7] for recent examples), concerned with features of the instantaneous velocity field driving the flow [8,9]. The resulting Eulerian coherent structure criteria have been broadly used in flow structure identification, although none has emerged as a definitive tool of choice.…”

Section: Introductionmentioning

confidence: 99%

Spectral-clustering approach to Lagrangian vortex detection

et al. 2016

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One of the ubiquitous features of real-life turbulent flows is the existence and persistence of coherent vortices. Here we show that such coherent vortices can be extracted as clusters of Lagrangian trajectories. We carry out the clustering on a weighted graph, with the weights measuring pairwise distances of fluid trajectories in the extended phase space of positions and time. We then extract coherent vortices from the graph using tools from spectral graph theory. Our method locates all coherent vortices in the flow simultaneously, thereby showing high potential for automated vortex tracking. We illustrate the performance of this technique by identifying coherent Lagrangian vortices in several two- and three-dimensional flows.

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Section: Introductionmentioning

confidence: 99%

Spectral-clustering approach to Lagrangian vortex detection

et al. 2016

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“…According to the K41 theory, the more energy turbulence extracts from largescale eddies, the more energy finescale eddies gain in the cascade process before energy dissipates (Kolmogorov 1941). The gained energy could entail the presence of finescale coherent structures, such as vortex tubes and strain sheets (Wilczek 2015;Dong et al 2020). Thus, clusterization intermittency manifesting itself in finescale coherent structures is typically larger in daytime than in nighttime (Fig.…”

Section: A Diurnal Variationmentioning

confidence: 99%

Finescale Clusterization Intermittency of Turbulence in the Atmospheric Boundary Layer

Liu

2020

Journal of the Atmospheric Sciences

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The intermittency of atmospheric turbulence plays an important role in the understanding of particle dispersal in the atmospheric boundary layer and in the statistical simulation of high-frequency wind speed in various applications. There are two kinds of intermittency, namely the magnitude intermittency (MI) related to non-Gaussianity and the less studied clusterization intermittency (CI) related to long-term correlation. In this paper, we use a 20 Hz ultrasonic data set lasting for one month to study CI of turbulent velocity fluctuations at different scales. Basing on the analysis of return time distribution of telegraphic approximation series, we propose to use the shape parameter of the Weibull distribution to measure CI. Observations of this parameter show that contrary to MI, CI tends to weaken as the scale increases. Besides, significant diurnal variations, showing that CI tends to strengthen at daytime (under unstable conditions) and weaken at nighttime (under stable conditions), are found at different observation heights. In the convective boundary layer, the mixed-layer similarity is found to scale CI exponent better than the Monin-Obukhov similarity. At night, CI is found to vary more slightly with height in the regime with large mean wind speeds than in the regime with small mean wind speeds, according to the Hockey-Stick theory.

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“…1. This organization-a sort of vortex-strain worm-rolls-is characteristic of turbulent flows [7][8][9][10], and its origin and dynamical implications continue to be investigated [11][12][13][14][15][16]. These structures distinguish fully developed turbulence from purely random flow fields, and must play an important role in many aspects of turbulent transport.…”

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confidence: 99%

Flow structures govern particle collisions in turbulence

et al. 2019

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The role of the spatial structure of a turbulent flow in enhancing particle collision rates in suspensions is an open question. We show and quantify, as a function of particle inertia, the correlation between the multiscale structures of turbulence and particle collisions: Straining zones contribute predominantly to rapid head-on collisions compared to vortical regions. We also discover the importance of vortex-strain worm-rolls, which goes beyond ideas of preferential concentration and may explain the rapid growth of aggregates in natural processes, such as the initiation of rain in warm clouds. * jrpicardo@icts.res.in;

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New insights into the fine-scale structure of turbulence

Cited by 4 publications

References 10 publications

Spectral-clustering approach to Lagrangian vortex detection

Spectral-clustering approach to Lagrangian vortex detection

Finescale Clusterization Intermittency of Turbulence in the Atmospheric Boundary Layer

Flow structures govern particle collisions in turbulence

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