3D Chaotic Model for Subgrid Turbulent Dispersion in Large Eddy Simulations

Abstract A 3D multiscale kinematic velocity field is introduced as a model to simulate Lagrangian turbulent dispersion. The incompressible velocity field is a nonlinear deterministic function, periodic in space and time, that generates chaotic mixing of Lagrangian trajectories. Relative dispersion properties, for example Richardson’s law, are correctly reproduced under two basic conditions: 1) the velocity amplitudes of the spatial modes must be related to the corresponding wavelengths through the Kolmogorov scaling and 2) the problem of the lack of a “sweeping effect” of the small eddies by the large eddies, common to kinematic simulations, has to be taken into account. It is shown that, as far as Lagrangian dispersion is concerned, the model presented herein can be successfully applied as an additional subgrid contribution for large eddy simulations of the planetary boundary layer flow.

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Effects of Reduced Mesh Resolution on Large Eddy Simulations of Atmospheric Boundary Layer Flow

10.1615/tfec2018.cfd.021721 ◽

2018 ◽

Author(s):

Matthew McKenna ◽

Ikramuddin Ahmed ◽

DongHun Yeo

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Boundary Layer Flow ◽

Large Eddy Simulations ◽

Large Eddy ◽

Mesh Resolution ◽

Layer Flow

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The Spatio-Temporal Intermittency of the Velocity Field in Low-Resolution Large-Eddy Simulations of Homogeneous Turbulence

Fluid Mechanics and Its Applications - Advances in Turbulence V ◽

10.1007/978-94-011-0457-9_9 ◽

1995 ◽

pp. 41-46

Author(s):

M. Briscolini ◽

P. Santangelo

Keyword(s):

Velocity Field ◽

Large Eddy Simulations ◽

Homogeneous Turbulence ◽

Low Resolution ◽

Large Eddy ◽

Spatio Temporal

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Can statistics of turbulent tracer dispersion be inferred from camera observations of SO<sub>2</sub> in the ultraviolet?

10.5194/amt-2019-286 ◽

2019 ◽

Author(s):

Arve Kylling ◽

Hamidreza Ardeshiri ◽

Massimo Cassiani ◽

Anna Solvejg Dinger ◽

Soon-Young Park ◽

...

Keyword(s):

Turbulent Dispersion ◽

Relative Dispersion ◽

Radiative Transfer Model ◽

Transfer Model ◽

Eddy Simulation ◽

Tracer Dispersion ◽

Large Eddy ◽

Sensitivity Studies ◽

Mean Differences ◽

Simulated Images

Abstract. Turbulence is one of the unsolved problems of physics. Atmospheric turbulence and in particular its effect on tracer dispersion may be measured by cameras sensitive to the absorption of ultraviolet (UV) sun-light by sulfur dioxide (SO2), a gas that can be considered a passive tracer over short transport distances. We present a method to simulate UV camera measurements of SO2 with a 3D Monte Carlo radiative transfer model which takes input from a large eddy simulation (LES) of a SO2 plume released from a point source. From the simulated images the apparent absorbance and various plume density statistics (centerline position, meandering, absolute and relative dispersion, skewness, and fractal dimension) were calculated. These were compared with corresponding quantities obtained directly from the LES. Mean differences of centerline position, absolute and relative dispersion, and skewness between the simulated images and the LES were found to be smaller than a quarter of one camera pixel, with standard deviations between 1/2 and 3/2 camera pixel. Furthermore sensitivity studies were made to quantify how changes in solar azimuth and zenith angles, aerosol loading (background and in plume), and surface albedo impact the UV camera image plume statistics. Changing the values of these parameters within realistic limits have negligible effect on the centerline position, meandering, absolute and relative dispersions, and skewness of the SO2 plume. Thus, we demonstrate that UV camera images of SO2 plumes may be used to derive plume statistics of relevance for the study of atmospheric turbulent dispersion.

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Drifter dispersion in the Adriatic Sea: Lagrangian data and chaotic model

Annales Geophysicae ◽

10.5194/angeo-19-121-2001 ◽

2001 ◽

Vol 19 (1) ◽

pp. 121-129 ◽

Cited By ~ 64

Author(s):

G. Lacorata ◽

E. Aurell ◽

A. Vulpiani

Keyword(s):

Nonlinear Dynamics ◽

Lyapunov Exponent ◽

Adriatic Sea ◽

Relative Dispersion ◽

Analysis Tool ◽

Standard Analysis ◽

Mixing Processes ◽

Chaotic Model ◽

Lagrangian Dispersion ◽

Lagrangian Data

Abstract. We analyze characteristics of drifter trajectories from the Adriatic Sea with recently introduced nonlinear dynamics techniques. We discuss how in quasi-enclosed basins, relative dispersion as a function of time, a standard analysis tool in this context, may give a distorted picture of the dynamics. We further show that useful information may be obtained by using two related non-asymptotic indicators, the Finite-Scale Lyapunov Exponent (FSLE) and the Lagrangian Structure Function (LSF), which both describe intrinsic physical properties at a given scale. We introduce a simple chaotic model for drifter motion in this system, and show by comparison with the model that Lagrangian dispersion is mainly driven by advection at sub-basin scales until saturation sets in.Key words. Oceanography: General (marginal and semi-closed seas) – Oceanography: Physical (turbulence, diffusion, and mixing processes; upper ocean processes)

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