scholarly journals Pollution Transport Patterns Obtained Through Generalized Lagrangian Coherent Structures

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 168
Author(s):  
Peter J. Nolan ◽  
Hosein Foroutan ◽  
Shane D. Ross
Keyword(s):  
Velocity Field ◽  
Coherent Structures ◽  
Initial Conditions ◽  
Saddle Points ◽  
Chemical Species ◽  
Lagrangian Coherent Structures ◽  
Time Interval ◽  
Pollution Transport ◽  
Material Transport ◽  
Material Surfaces

Identifying atmospheric transport pathways is important to understand the effects of pollutants on weather, climate, and human health. The atmospheric wind field is variable in space and time and contains complex patterns due to turbulent mixing. In such a highly unsteady flow field, it can be challenging to predict material transport over a finite-time interval. Particle trajectories are often used to study how pollutants evolve in the atmosphere. Nevertheless, individual trajectories are sensitive to their initial conditions. Lagrangian Coherent Structures (LCSs) have been shown to form the template of fluid parcel motion in a fluid flow. LCSs can be characterized by special material surfaces that organize the parcel motion into ordered patterns. These key material surfaces form the core of fluid deformation patterns, such as saddle points, tangles, filaments, barriers, and pathways. Traditionally, the study of LCSs has looked at coherent structures derived from integrating the wind velocity field. It has been assumed that particles in the atmosphere will generally evolve with the wind. Recent work has begun to look at the motion of chemical species, such as water vapor, within atmospheric flows. By calculating the flux associated with each species, a new effective flux-based velocity field can be obtained for each species. This work analyzes generalized species-weighted coherent structures associated with various chemical species to find their patterns and pathways in the atmosphere, providing a new tool and language for the assessment of pollutant transport and patterns.

Lower thermospheric material transport via Lagrangian coherent structures

2021 ◽  
Author(s):  
S. Datta‐Barua ◽  
N. Pedatella ◽  
K. R. Greer ◽  
N. Wang ◽  
L. Nutter ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Lagrangian Coherent Structures ◽  
Material Transport

scholarly journals Numerical investigation of lagrangian coherent structures in steady rotation vortex shedding control

2021 ◽  
Author(s):  
Muhammad Hashir ◽  
◽  
Tauseef -ur-Rehman ◽  
Aamir Sohail ◽  
Muhammad Yasar Javaid ◽  
...  
Keyword(s):  
Dynamical System ◽  
Vortex Shedding ◽  
Coherent Structures ◽  
Invariant Manifolds ◽  
Saddle Points ◽  
Lagrangian Coherent Structures ◽  
Speed Ratio ◽  
Cylinder Wall ◽  
Steady Rotation ◽  
Autonomous Dynamical System

In this paper, vortex shedding and suppression are numerically investigated as autonomous and non-autonomous dynamical systems respectively. Lagrangian coherent structures (LCSs) are used as a numerical tool to analyze these systems. These structures are ridges of Finite time Lyapunov exponent (FTLE) which act as material surfaces that are transport barriers within the flow. Initially, the utility of LCSs is explored for revealing the coherent structures of these systems. Finally, an active flow control method, steady rotation is applied to the non-autonomous dynamical system with different speed ratios to mitigate vortex shedding magnitude. This will eventually turn the system into an autonomous system. Fixed saddle points, separation profiles essentially as unstable time variant manifolds attached to cylinder wall and evolution of other unstable manifolds with variant speed ratios are analyzed with reference to LCSs. It is revealed that speed ratio of 2.1 fully suppresses the von Karman vortex street at Reynolds number of 100 and system turns into an autonomous dynamical system with fixed saddle points and time-invariant manifolds.

Experimental Analysis of Lagrangian Coherent Structures and Chaotic Mixing in Rayleigh-Benard Convection

2020 ◽  
Author(s):  
Masahito Watanabe ◽  
Yusuke Kitamura ◽  
Naoki Hatta ◽  
Hiroaki Yoshimura
Keyword(s):  
Velocity Field ◽  
Coherent Structures ◽  
Lagrangian Coherent Structures ◽  
Chaotic Mixing ◽  
Lagrangian Description ◽  
Two Dimensional ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Abstract It is known that some fluid particles may be transported chaotically in Lagrangian description although the velocity field seems to be stable in Eulerian description. A typical example can be found in the system of two-dimensional Rayleigh-Benard convection with perturbed velocity fields, which has been investigated as a low dimensional mechanical model of fluid phenomena associated with natural convection in order to clarify the mechanism of fluid transport (see, for instance, [2]). In this study, we make an experimental study on the global structures of chaotic mixing appeared in the two-dimensional perturbed Rayleigh-Benard convection by analyzing Lagrangian coherent structures (LCSs), which correspond to the invariant manifolds of time-dependent mechanical systems. We develop an apparatus to measure the velocity field by Particle Image Velocimetry (PIV) and then show the LCSs which can be numerically detected from the experimental data by computing Finite-time Lyapunov exponent (FTLE) fields. Finally, we show the global structures of chaotic mixing appeared in the perturbed Rayleigh-Benard convection as well as the steady convection by experiments. In particular, we clarify how the LCSs are entangled with each other around the cell boundaries to carry out chaotic Lagrangian transports.

scholarly journals Lagrangian coherent structures and material transport in unsteady flow of vertical-axis turbine wakes

AIP Advances ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 085001
Author(s):  
Kun Wang ◽  
Li Zou ◽  
Jiuming Zhang ◽  
Yichen Jiang ◽  
Peidong Zhao
Keyword(s):  
Unsteady Flow ◽  
Coherent Structures ◽  
Vertical Axis ◽  
Lagrangian Coherent Structures ◽  
Material Transport ◽  
Vertical Axis Turbine

Persistency of debris accumulation in tidal estuaries using Lagrangian coherent structures

2021 ◽  
pp. 146808
Author(s):  
Anusmriti Ghosh ◽  
Kabir Suara ◽  
Scott W. McCue ◽  
Yingying Yu ◽  
Tarmo Soomere ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Lagrangian Coherent Structures ◽  
Debris Accumulation ◽  
Tidal Estuaries

Lagrangian coherent structures deduced from HF radar measurements

2015 ◽  
Author(s):  
Francesco Enrile ◽  
Giovanni Besio ◽  
Marcello G. Magaldi ◽  
Carlo Mantovani ◽  
Simone Cosoli ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Hf Radar ◽  
Lagrangian Coherent Structures ◽  
Radar Measurements

scholarly journals Fine-scale structures as spots of increased fish concentration in the open ocean

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alberto Baudena ◽  
Enrico Ser-Giacomi ◽  
Donatella D’Onofrio ◽  
Xavier Capet ◽  
Cedric Cotté ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Trophic Levels ◽  
Fish Distribution ◽  
Lagrangian Coherent Structures ◽  
Mesopelagic Fish ◽  
Fine Scale ◽  
Conservation Policies ◽  
Top Predators ◽  
Frontal Zones ◽  
Spatio Temporal

AbstractOceanic frontal zones have been shown to deeply influence the distribution of primary producers and, at the other extreme of the trophic web, top predators. However, the relationship between these structures and intermediate trophic levels is much more obscure. In this paper we address this knowledge gap by comparing acoustic measurements of mesopelagic fish concentrations to satellite-derived fine-scale Lagrangian Coherent Structures in the Indian sector of the Southern Ocean. First, we demonstrate that higher fish concentrations occur more frequently in correspondence with strong Lagrangian Coherent Structures. Secondly, we illustrate that, while increased fish densities are more likely to be observed over these structures, the presence of a fine-scale feature does not imply a concomitant fish accumulation, as other factors affect fish distribution. Thirdly, we show that, when only chlorophyll-rich waters are considered, front intensity modulates significantly more the local fish concentration. Finally, we discuss a model representing fish movement along Lagrangian features, specifically built for mid-trophic levels. Its results, obtained with realistic parameters, are qualitatively consistent with the observations and the spatio-temporal scales analysed. Overall, these findings may help to integrate intermediate trophic levels in trophic models, which can ultimately support management and conservation policies.

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