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

2018 ◽  
Vol 59 (5) ◽  
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

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

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Johannes Bosbach ◽  
Daniel Schanz ◽  
Phillip Godbersen ◽  
Andreas Schröder
Keyword(s):  
Particle Tracking ◽  
Large Scale ◽  
Torsional Oscillation ◽  
Cylindrical Sample ◽  
Small Scale ◽  
Lagrangian Particle Tracking ◽  
Lagrangian Particle ◽  
Thermal Plumes ◽  
Dynamic Events ◽  
Lpt Algorithm

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.

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

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.

scholarly journals TrackFit: Uncertainty Quantification, Optimal Filtering and Interpolation of Tracks for Time-Resolved Lagrangian Particle Tracking

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Sebastian Gesemann
Keyword(s):  
Uncertainty Quantification ◽  
Particle Tracking ◽  
Optimal Choice ◽  
Optimal Filtering ◽  
Lagrangian Particle Tracking ◽  
Lagrangian Particle ◽  
Time Resolved ◽  
Filtering Method ◽  
Power Spectral ◽  
And Performance

Advanced Lagrangian Particle Tracking methods (such as the STB algorithm (Schanz et al. 2016)) are a very useful tool for uncovering properties of flow. As a measurement technique, the results of such methods are perturbed by different sources of errors and noise. This work addresses the problem of optimal filtering of particle tracks as well as estimating uncertainties of derived quantities such as location, velocity and acceleration of observed particles. The behavior and performance of this new filtering method (“TrackFit”), first introduced at Gesemann et al. (2016) is analyzed and compared to the Savitzky–Golay filter (Savitzky and Golay (1964)) which is commonly used for these purposes. The optimal choice of parameters of this filtering method as well as the uncertainty quantification of the reconstructed tracks can be extracted from a spectral analysis of the recorded raw particle tracking data. This is in contrast to a Savitzky–Golay filter where the choice of parameters might often be driven by experience and gut feeling. Estimating the power spectral density (PSD) of the particle trajectory signals for the purpose of optimal filtering parameter selection represents a challenge due to possibly short trajectory signals. In the following work we will present a method for PSD estimation that is applicable in this scenario. In addition, we show that regardless of the choice of Savitzky–Golay filter parameters, the resulting filter will not approximate the ideal noise reduction filter well unlike the “TrackFit” described in this work.

scholarly journals Main results of the first Lagrangian Particle Tracking Challenge

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Andrea Sciacchitano ◽  
Benjamin Leclaire ◽  
Andreas Schroeder
Keyword(s):  
Particle Tracking ◽  
Tracer Particle ◽  
Time Instant ◽  
Lagrangian Particle Tracking ◽  
Lagrangian Particle ◽  
Time Resolved ◽  
Horizon 2020 ◽  
Tracer Particles ◽  
Acquisition Strategies ◽  
Particle Images

This work presents the main results of the first Lagrangian Particle Tracking challenge, conducted within the framework of the European Union’s Horizon 2020 project HOMER (Holistic Optical Metrology for Aero-Elastic Research), grant agreement number 769237. The challenge, jointly organised by the research groups of DLR, ONERA and TU Delft, considered a synthetic experiment reproducing the wall-bounded flow in the wake of a cylinder which was simulated by LES. The participants received the calibration images and sets of particle images acquired by four virtual cameras, and were asked to produce as output the particles positions, velocities and accelerations (when possible) at a specific time instant. Four different image acquisition strategies were addressed, namely two-pulse (TP), four-pulse (FP) and time-resolved (TR) acquisitions, each with varying tracer particle concentrations (or number of particles per pixel, ppp). The participants’ outputs were analysed in terms of percentages of correctly reconstructed particles, missed particles, ghost particles, correct tracks and wrong tracks, as well as in terms of position, velocity and acceleration errors, along with their distributions. The analysis of the results showed that the best-performing algorithms allow for a correct reconstruction of more than 99% of the tracer particles with positional errors below 0.1 pixels even at ppp values exceeding 0.15, whereas other algorithms are more prone to the presence of ghost particles already for ppp < 0.1. While the velocity errors remained contained within a small percentage of the bulk velocity, acceleration errors as large as 50% of the actual acceleration magnitude were retrieved.

scholarly journals First challenge on Lagrangian Particle Tracking and Data Assimilation: datasets description and planned evolution to an open online benchmark

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Benjamin Leclaire ◽  
Ivan Mary ◽  
Cédric Liauzun ◽  
Stéphanie Péron ◽  
Andrea Sciacchitano ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Particle Tracking ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Lagrangian Particle Tracking ◽  
Lagrangian Particle ◽  
Pressure Fields ◽  
Significant Research

In the last decade, Lagrangian Particle Tracking (LPT) has emerged as one of the leading measurement techniques for the quantitative determination of fluid flows in three-dimensional domains (see e.g. Schanz et al., 2016), due to its accuracy in reconstructing particles velocities and material accelerations. Due to the scattered nature of the obtained result, at the particles positions only, significant research efforts have also been placed in the development of dedicated Data Assimilation (DA) techniques, aiming at finally reconstructing full 3D velocity and pressure fields on regular Cartesian grids (see, e.g., Schneiders et al. 2016).

scholarly journals Investigation of turbulent boundary layer flows with adverse pressure gradient by means of 3D Lagrangian particle tracking with Shake-The-Box

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Matteo Novara ◽  
Daniel Schanz ◽  
Reinhard Geisler ◽  
Janos Agocs ◽  
Felix Eich ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Large Scale ◽  
Adverse Pressure Gradient ◽  
Spanwise Direction ◽  
Streamwise Direction ◽  
Lagrangian Particle Tracking ◽  
Lagrangian Particle ◽  
Time Resolved ◽  
Logarithmic Region

A large-scale 3D Lagrangian particle tracking (LPT) investigation of a turbulent boundary layer (TBL) flow developing across different pressure gradient regions is presented in this study. Three high-speed multi-camera imaging systems, LED illumination and helium-filled soap bubbles (HFSB) tracers have been adopted to produce time-resolved sequences of particle images over a large volume encompassing approximately 3 m in the streamwise direction, 0:8 m in the spanwise direction and 0:25 m in the wall-normal direction. Individual tracers have been reconstructed and tracked within the imaged volume by means of the Shake-The-Box algorithm (STB, Schanz et al. (2016)); the FlowFit data assimilation algorithm (Gesemann et al. (2016)) has been used to evaluate the spatial velocity gradients and to interpolate the scattered LPT results onto a regular grid. Thanks to the large size of the investigated volume and to the time-resolved nature of the recorded images, the entire spatial extent of the large-scale coherent motions within the logarithmic region of the TBL (i.e. superstructures) could be captured and their dynamics investigated during their development over several boundary layer thickness in the streamwise direction, from the zero pressure gradient region (ZPG) to the adverse pressure gradient region (APG). Two free-stream velocities were investigated, namely 7 and 14m=s, corresponding to Ret ~ 3,000 and 5,000 respectively. The results confirm the location and scale of the elongated high- and low-momentum structures in the logarithmic region, as well as their meandering in the spanwise direction. Two-point correlation statistics show that the width and spacing of the superstructures are not affected by the transition from the ZPG to the APG region. The analysis of the instantaneous flow realizations from both a Lagrangian and Eulerian perspective indicates the presence of significant fluid particle elements exchange across the interfaces of the large-scale structures.

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

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.

scholarly journals Eddy Cancellation of the Ekman Cell in Subtropical Gyres

2016 ◽  
Vol 46 (10) ◽  
pp. 2995-3010 ◽  
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.”

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

2010 ◽  
Vol 133 (1) ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document