Spatially and temporally resolved measurements of turbulent Rayleigh-Bénard convection by Lagrangian particle tracking of long-lived helium-filled soap bubbles

We present spatially and temporally resolved velocity and acceleration measurements of turbulent RayleighBénard convection spanning the whole volume (~ 1 m³) of a cylindrical sample with aspect ratio one. With the "Shake-The-Box" (STB) Lagrangian particle tracking (LPT) algorithm, we were able to instantaneously track up to 560,000 particles, corresponding to mean inter-particle distances down to 6 - 8 Kolmogorov lengths. We used the data assimilation scheme ‘FlowFit’, which involves continuity and Navier-Stokesconstraints, to map the scattered velocity and acceleration data on cubic grids, herewith recovering the smallest flow scales. Lagrangian and Eulerian visualizations reveal the dynamics of the large-scale circulation and its interplay with small scale structures, such as thermal plumes and turbulent background fluctuations. As a result, the complex time-dependent behavior of the LSC comprising azimuthal rotations, torsional oscillation and sloshing can be extracted from the data. Further, we found more seldom dynamic events, such as spontaneous reorientations of the LSC in the data from long-term measurements.

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Time-resolved large-scale volumetric pressure fields of an impinging jet from dense Lagrangian particle tracking

Experiments in Fluids ◽

10.1007/s00348-018-2533-0 ◽

2018 ◽

Vol 59 (5) ◽

Cited By ~ 8

Author(s):

F. Huhn ◽

D. Schanz ◽

P. Manovski ◽

S. Gesemann ◽

A. Schröder

Keyword(s):

Particle Tracking ◽

Large Scale ◽

Impinging Jet ◽

Lagrangian Particle Tracking ◽

Lagrangian Particle ◽

Time Resolved ◽

Pressure Fields

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CFD Prediction of Particle Deposition in Large-Scale Human Lung Models

Volume 2: Biomedical and Biotechnology Engineering ◽

10.1115/imece2010-39406 ◽

2010 ◽

Author(s):

D. Keith Walters ◽

William H. Luke

Keyword(s):

Particle Tracking ◽

Particle Transport ◽

Particle Deposition ◽

Large Scale ◽

Human Lung ◽

Computational Cost ◽

Lagrangian Particle Tracking ◽

Lagrangian Particle ◽

Order Of Magnitude ◽

Intractable Problem

Computational fluid dynamics (CFD) has evolved as a useful tool for the prediction of airflow and particle transport within the human lung airway. A large number of published studies have demonstrated the use of CFD coupled with Lagrangian particle tracking methods to determine local and regional deposition rates in small subsections of the bronchopulmonary tree. However, simulation of particle transport and deposition in large-scale models encompassing more than a few generations is less common, due primarily to the sheer size and complexity of the human lung airway geometry. Fully coupled flowfield solution and particle tracking in the entire lung, for example, is currently an intractable problem and will remain so for the foreseeable future. This paper adopts a previously reported methodology for simulating large-scale regions of the lung airway [1], which was shown to produce results similar to fully resolved geometries using approximate, reduced geometry models. The methodology is here extended to particle transport and deposition simulations. Lagrangian particle-tracking simulations are performed in combination with Eulerian simulations of the air flow in an idealized representation of the human lung airway tree. Results using the reduced models are compared to fully resolved models for an eight-generation region of the conducting zone. Agreement between fully resolved and reduced geometry simulations indicates that the new method can provide an accurate alternative for large-scale CFD simulations while reducing the computational cost of these simulations by an order of magnitude or more.

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Large-scale 3D flow investigations around a cyclically breathing thermal manikin in a 12 m³ room using HFSB and STB

14th International Symposium on Particle Image Velocimetry ◽

10.18409/ispiv.v1i1.204 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Andreas Schröder ◽

Daniel Schanz ◽

Johannes Bosbach ◽

Matteo Novara ◽

Reinhard Geisler ◽

...

Keyword(s):

Particle Tracking ◽

Large Scale ◽

Virus Transmission ◽

Mitigation Strategies ◽

Thermal Manikin ◽

Lagrangian Particle Tracking ◽

Lagrangian Particle ◽

Infection Dynamics ◽

Key Factor ◽

Passive Tracers

Exhalation of small aerosol droplets and their transport, dispersion and (local) accumulation in closed rooms have been identified as the main pathway for indirect or airborne respiratory virus transmission from person to person, e.g. for SARS-CoV 2 or measles (Morawska and Cao 2020). Understanding airborne transport mechanisms of viruses via small bio-aerosol particles inside closed populated rooms is an important key factor for optimizing various mitigation strategies (Morawska et al. 2020), which can play an important role for damping the infection dynamics of any future and the ongoing present pandemic scenario, which unfortunately, is still threatening due to the spreading of several SARS-CoV2 variants of concern, e.g. delta (Kupferschmidt and Wadman 2021). Therefore, a large-scale 3D Lagrangian Particle Tracking experiment using up to 3 million long lived and nearly neutrally buoyant helium-filled soap bubbles (HFSB) with a mean diameter of ~ 370 µm as passive tracers in a 12 m³ generic test room has been performed, which allows to fully resolve the Lagrangian transport properties and flow field inside the whole room around a cyclically breathing thermal manikin (Lange et al. 2012) with and without mouth-nose-masks and shields applied. Six high-resolution CMOS streaming cameras, a large array of powerful pulsed LEDs have been used and the Shake-The-Box (STB) (Schanz et al. 2016) Lagrangian particle tracking algorithm has been applied in this experimental study of internal flows in order to gain insight into the complex transient and turbulent aerosol particle transport and dispersion processes around seated breathing persons.

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Eddy Cancellation of the Ekman Cell in Subtropical Gyres

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0097.1 ◽

2016 ◽

Vol 46 (10) ◽

pp. 2995-3010 ◽

Cited By ~ 9

Author(s):

Edward W. Doddridge ◽

David P. Marshall ◽

Andrew McC. Hogg

Keyword(s):

Biological Activity ◽

Southern Ocean ◽

Wind Stress ◽

Particle Tracking ◽

Potential Vorticity ◽

Large Scale ◽

Ekman Pumping ◽

Lagrangian Particle Tracking ◽

Lagrangian Particle ◽

Wind Stress Curl

AbstractThe presence of large-scale Ekman pumping associated with the climatological wind stress curl is the textbook explanation for low biological activity in the subtropical gyres. Using an idealized, eddy-resolving model, it is shown that Eulerian-mean Ekman pumping may be opposed by an eddy-driven circulation, analogous to the way in which the atmospheric Ferrel cell and the Southern Ocean Deacon cell are opposed by eddy-driven circulations. Lagrangian particle tracking, potential vorticity fluxes, and depth–density streamfunctions are used to show that, in the model, the rectified effect of eddies acts to largely cancel the Eulerian-mean Ekman downwelling. To distinguish this effect from eddy compensation, it is proposed that the suppression of Eulerian-mean downwelling by eddies be called “eddy cancellation.”

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Computational Fluid Dynamics Simulations of Particle Deposition in Large-Scale, Multigenerational Lung Models

Journal of Biomechanical Engineering ◽

10.1115/1.4002936 ◽

2010 ◽

Vol 133 (1) ◽

Cited By ~ 35

Author(s):

D. Keith Walters ◽

William H. Luke

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Particle Tracking ◽

Particle Transport ◽

Particle Deposition ◽

Large Scale ◽

Human Lung ◽

Lagrangian Particle Tracking ◽

Lagrangian Particle ◽

Cfd Simulations

Computational fluid dynamics (CFD) has emerged as a useful tool for the prediction of airflow and particle transport within the human lung airway. Several published studies have demonstrated the use of Eulerian finite-volume CFD simulations coupled with Lagrangian particle tracking methods to determine local and regional particle deposition rates in small subsections of the bronchopulmonary tree. However, the simulation of particle transport and deposition in large-scale models encompassing more than a few generations is less common, due in part to the sheer size and complexity of the human lung airway. Highly resolved, fully coupled flowfield solution and particle tracking in the entire lung, for example, is currently an intractable problem and will remain so for the foreseeable future. This paper adopts a previously reported methodology for simulating large-scale regions of the lung airway (Walters, D. K., and Luke, W. H., 2010, “A Method for Three-Dimensional Navier–Stokes Simulations of Large-Scale Regions of the Human Lung Airway,” ASME J. Fluids Eng., 132(5), p. 051101), which was shown to produce results similar to fully resolved geometries using approximate, reduced geometry models. The methodology is extended here to particle transport and deposition simulations. Lagrangian particle tracking simulations are performed in combination with Eulerian simulations of the airflow in an idealized representation of the human lung airway tree. Results using the reduced models are compared with those using the fully resolved models for an eight-generation region of the conducting zone. The agreement between fully resolved and reduced geometry simulations indicates that the new method can provide an accurate alternative for large-scale CFD simulations while potentially reducing the computational cost of these simulations by several orders of magnitude.

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