A robust and accurate technique for Lagrangian tracking of bubbles and detecting fragmentation and coalescence

2021 ◽  
Vol 135 ◽  
pp. 103523
Author(s):  
Qiang Gao ◽  
Grant B. Deane ◽  
Han Liu ◽  
Lian Shen
Keyword(s):  
Lagrangian Tracking

scholarly journals A parameterization of local and remote tidal mixing

2020 ◽  
Author(s):  
Casimir de Lavergne ◽  
Clément Vic ◽  
Gurvan Madec ◽  
Fabien Roquet ◽  
Amy Waterhouse ◽  
...  
Keyword(s):  
Vertical Mixing ◽  
Three Dimensional ◽  
Internal Tide ◽  
Ocean Model ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Global Ocean ◽  
Energy Conserving ◽  
Energy Constrained ◽  
Lagrangian Tracking

<p>Vertical mixing is often regarded as the Achilles’ heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. Implemented in the NEMO global ocean model, the scheme improves the representation of deep water-mass transformation and obviates the need for a constant background diffusivity.</p>

Effects of the laryngeal jet on nano- and microparticle transport and deposition in an approximate model of the upper tracheobronchial airways

2008 ◽  
Vol 104 (6) ◽  
pp. 1761-1777 ◽  
Author(s):  
Jinxiang Xi ◽  
P. Worth Longest ◽  
Ted B. Martonen
Keyword(s):  
Reverse Flow ◽  
Approximate Model ◽  
In Vitro Models ◽  
Deposition Density ◽  
Flow Features ◽  
Tracking Model ◽  
Induced Flow ◽  
Lagrangian Tracking ◽  
The Right

The extent to which laryngeal-induced flow features penetrate into the upper tracheobronchial (TB) airways and their related impact on particle transport and deposition are not well understood. The objective of this study was to evaluate the effects of including the laryngeal jet on the behavior and fate of inhaled aerosols in an approximate model of the upper TB region. The upper TB model was based on a simplified numerical reproduction of a replica cast geometry used in previous in vitro deposition experiments that extended to the sixth respiratory generation along some paths. Simulations with and without an approximate larynx were performed. Particle sizes ranging from 2.5 nm to 12 μm were considered using a well-tested Lagrangian tracking model. The model larynx was observed to significantly affect flow dynamics, including a laryngeal jet skewed toward the right wall of the trachea and a significant reverse flow in the left region of the trachea. Inclusion of the laryngeal model increased the tracheal deposition of nano- and micrometer particles by factors ranging from 2 to 10 and significantly reduced deposition in the first three bronchi of the model. Considering localized conditions, inclusion of the laryngeal approximation decreased deposition at the main carina and produced a maximum in local surface deposition density in the lobar-to-segmental bifurcations (G2–G3) for both 40-nm and 4-μm aerosols. These findings corroborate previous experiments and highlight the need to include a laryngeal representation in future computational and in vitro models of the TB region.

Lagrangian tracking of soot particles in LES of gas turbines

2019 ◽  
Vol 37 (4) ◽  
pp. 5429-5436 ◽  
Author(s):  
Lucien Gallen ◽  
Anne Felden ◽  
Eleonore Riber ◽  
Bénédicte Cuenot
Keyword(s):  
Gas Turbines ◽  
Soot Particles ◽  
Lagrangian Tracking

scholarly journals Extreme westward surface drift in the North Sea: Public reports of stranded drifters and Lagrangian tracking

2019 ◽  
Vol 177 ◽  
pp. 24-32 ◽  
Author(s):  
E.V. Stanev ◽  
T.H. Badewien ◽  
H. Freund ◽  
S. Grayek ◽  
F. Hahner ◽  
...  
Keyword(s):  
North Sea ◽  
The North ◽  
The North Sea ◽  
Lagrangian Tracking ◽  
Surface Drift

Study of Sand Particle Trajectories and Erosion Into the First Compression Stage of a Turbofan

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Equations Of Motion ◽  
Leading Edge ◽  
Sand Particle ◽  
The Finite Element Method ◽  
Particle Trajectories ◽  
Compression Stage ◽  
Trailing Edges ◽  
Blade Tip ◽  
Lagrangian Tracking ◽  
Aero Engines

Aero-engines operating in dusty environments are subject to ingestion of erodent particles leading to erosion damage of blades and a permanent drop in performance. This work concerns the study of particle dynamics and erosion of the front compression stage of a commercial turbofan. Particle trajectories simulations used a stochastic Lagrangian tracking code that solves the equations of motion separately from the airflow in a stepwise manner, while the tracking of particles in different cells is based on the finite element method. As the locations of impacts and rates of erosion were predicted, the subsequent geometry deteriorations were assessed. The number of particles, sizes, and initial positions were specified conformed to sand particle distribution (MIL-E5007E, 0-1000 micrometers) and concentrations 50–700 mg/m3. The results show that the IGV blade is mainly eroded over the leading edge and near hub and shroud; also the rotor blade has a noticeable erosion of the leading and trailing edges and a rounding of the blade tip corners, whereas in the diffuser, erosion is shown to spread over the blade surfaces in addition to the leading edge and trailing edge.

Simulation of Heat Transfer With LBM and Lagrangian Methods for Microfluidic Applications

2005 ◽  
Author(s):  
Nishitha Thummala ◽  
Dimitrios V. Papavassiliou
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Lattice Boltzmann ◽  
Constant Heat Flux ◽  
Fully Developed Flow ◽  
Thermal Boundary Conditions ◽  
Lattice Boltzmann Simulation ◽  
Lagrangian Tracking ◽  
Boltzmann Method ◽  
Single Flow

This work presents a Lagrangian approach to simulate convective heat transfer in small scales. The fully developed flow field, simulated by a Lattice Boltzmann Method, is combined with Lagrangian tracking of thermal markers to determine the behavior of an instantaneous scalar line source located at the wall of a channel. The resulting probability density functions are used to calculate the behavior of continuous line sources of heat at the wall of the channel, as well as the temperature for the case of constant temperature or constant heat flux from the wall. This method is resourceful in terms of computational efficiency, in that it can be used to simulate various thermal boundary conditions and Prandtl number fluids with a single flow field resulting from a Lattice Boltzmann simulation.

scholarly journals Intraseasonal and Interannual Variability in North American Storm Tracks and Its Relationship to Equatorial Pacific Variability

2013 ◽  
Vol 141 (10) ◽  
pp. 3610-3625 ◽  
Author(s):  
Kevin M. Grise ◽  
Seok-Woo Son ◽  
John R. Gyakum
Keyword(s):  
North America ◽  
Interannual Variability ◽  
North American ◽  
Southern Oscillation ◽  
Extratropical Cyclones ◽  
The North ◽  
The Pacific ◽  
Cyclone Tracks ◽  
Lagrangian Tracking ◽  
The North Atlantic Oscillation

Abstract Extratropical cyclones play a principal role in wintertime precipitation and severe weather over North America. On average, the greatest number of cyclones track 1) from the lee of the Rocky Mountains eastward across the Great Lakes and 2) over the Gulf Stream along the eastern coastline of North America. However, the cyclone tracks are highly variable within individual winters and between winter seasons. In this study, the authors apply a Lagrangian tracking algorithm to examine variability in extratropical cyclone tracks over North America during winter. A series of methodological criteria is used to isolate cyclone development and decay regions and to account for the elevated topography over western North America. The results confirm the signatures of four climate phenomena in the intraseasonal and interannual variability in North American cyclone tracks: the North Atlantic Oscillation (NAO), the El Niño–Southern Oscillation (ENSO), the Pacific–North American pattern (PNA), and the Madden–Julian oscillation (MJO). Similar signatures are found using Eulerian bandpass-filtered eddy variances. Variability in the number of extratropical cyclones at most locations in North America is linked to fluctuations in Rossby wave trains extending from the central tropical Pacific Ocean. Only over the far northeastern United States and northeastern Canada is cyclone variability strongly linked to the NAO. The results suggest that Pacific sector variability (ENSO, PNA, and MJO) is a key contributor to intraseasonal and interannual variability in the frequency of extratropical cyclones at most locations across North America.

An Investigation of Crossing Trajectory Effects in Turbulent Shear Flow (Keynote)

2005 ◽  
Author(s):  
Lionel Thomas ◽  
Benoiˆt Oesterle´
Keyword(s):  
Shear Flow ◽  
Isotropic Turbulence ◽  
Fluid Velocity ◽  
Stokes Number ◽  
Turbulent Shear ◽  
Inertial Particles ◽  
Turbulent Shear Flow ◽  
Velocity Magnitude ◽  
Dispersed Particles ◽  
Lagrangian Tracking

The dispersion of small inertial particles moving in a homogeneous, hypothetically stationary, shear flow is investigated using both theoretical analysis and numerical simulation, under one-way coupling approximation. In the theoretical approach, the previous studies are extended to the case of homogeneous shear flow with a corresponding anisotropic spectrum. As it is impossible to obtain a closed theoretical solution without some drastic simplifications, the motion of dispersed particles is also investigated using kinematic simulation where random Fourier modes are generated according to a prescribed anisotropic spectrum with a superimposed linear mean fluid velocity profile. The combined effects of particle Stokes number and dimensionless drift velocity (magnitude and direction) are investigated by computing the statistics from Lagrangian tracking of a large number of particles in many flow field realizations, and comparison is made between the observed effects in shear flow and in isotropic turbulence.

scholarly journals Airflow and Particle Deposition in Acinar Models with Interalveolar Septal Walls and Different Alveolar Numbers

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Jinxiang Xi ◽  
Mohamed Talaat ◽  
Hesham Tanbour ◽  
Khaled Talaat
Keyword(s):  
Deposition Rate ◽  
Particle Deposition ◽  
Orientation Angle ◽  
Structural Complexity ◽  
Particle Dispersion ◽  
Breath Holding ◽  
Complex Models ◽  
Tracking Model ◽  
Lagrangian Tracking ◽  
Collateral Ventilation

Unique features exist in acinar units such as multiple alveoli, interalveolar septal walls, and pores of Kohn. However, the effects of such features on airflow and particle deposition remain not well quantified due to their structural complexity. This study aims to numerically investigate particle dynamics in acinar models with interalveolar septal walls and pores of Kohn. A simplified 4-alveoli model with well-defined geometries and a physiologically realistic 45-alveoli model was developed. A well-validated Lagrangian tracking model was used to simulate particle trajectories in the acinar models with rhythmically expanding and contracting wall motions. Both spatial and temporal dosimetries in the acinar models were analyzed. Results show that collateral ventilation exists among alveoli due to pressure imbalance. The size of interalveolar septal aperture significantly alters the spatial deposition pattern, while it has an insignificant effect on the total deposition rate. Surprisingly, the deposition rate in the 45-alveoli model is lower than that in the 4-alveoli model, indicating a stronger particle dispersion in more complex models. The gravity orientation angle has a decreasing effect on acinar deposition rates with an increasing number of alveoli retained in the model; such an effect is nearly negligible in the 45-alveoli model. Breath-holding increased particle deposition in the acinar region, which was most significant in the alveoli proximal to the duct. Increasing inhalation depth only slightly increases the fraction of deposited particles over particles entering the alveolar model but has a large influence on dispensing particles to the peripheral alveoli. Results of this study indicate that an empirical correlation for acinar deposition can be developed based on alveolar models with reduced complexity; however, what level of geometry complexity would be sufficient is yet to be determined.

scholarly journals Direct Lagrangian tracking simulation of droplet growth in vertically developing cloud

2018 ◽  
Vol 18 (22) ◽  
pp. 16619-16630 ◽  
Author(s):  
Yuichi Kunishima ◽  
Ryo Onishi
Keyword(s):  
Cloud Condensation Nuclei ◽  
Ground Surface ◽  
Droplet Growth ◽  
Back Trajectory ◽  
Lagrangian Statistics ◽  
Lagrangian Simulation ◽  
Comparison Results ◽  
Snow Crystals ◽  
Lagrangian Tracking ◽  
Condensational Growth

Abstract. We present a direct Lagrangian simulation that computes key warm-rain processes in a vertically developing cloud, including cloud condensation nuclei (CCN) activation, condensational growth, collisional growth, and droplet gravitational settling. This simulation, which tracks the motion and growth of individual particles, is applied to a kinematic simulation of an extremely vertically elongated quasi-one-dimensional domain, after which the results are compared with those obtained from a spectral-bin model, which adopts the conventional Eulerian framework. The comparison results, which confirm good bulk statistical agreement between the Lagrangian and conventional spectral-bin simulations, also show that the Lagrangian simulation is free from the numerical diffusion found in the spectral-bin simulation. After analyzing the Lagrangian statistics of the surface raindrops that reach the ground surface, back-trajectory scrutiny reveals that the Lagrangian statistics of surface raindrops contains the information about the sky where the raindrops grow like the shape does for snow crystals.

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