Lagrangian Particle Tracking Algorithm Research Articles

The Effect of Model Input Uncertainty on the Simulation of Typical Pollutant Transport in the Coastal Waters of China

Route planning to evade potential pollution holds critical importance for aquaculture vessels. This study establishes a fish-feed pollutant drift model based on the Lagrangian particle tracking algorithm and designs four sets of sensitivity experiments in the East China Sea. The research investigates the impact of model input uncertainties on the drift trajectory, centroid position, and sweeping area of the fish-feed pollutants. Numerical results indicate that the uncertainty in the background flow field significantly affects the uncertainty in the centroid position and sweeping area in the numerical simulations. Specifically, when a 35% random error is added to the background flow field, the centroid shift distance reaches its maximum, and the sweeping area also attains its largest value. The uncertainty in the background wind field affects the centroid position of particles but to a much lesser extent compared to the background flow field. When considering only the uncertainty of the background wind field, the sweeping area does not significantly differ from the control experiment as the uncertainty of the background wind field increases. The initial release position has little effect on the drift direction of the fish-feed pollutants but does affect the drift distance; it has minimal impact on the trajectory but significantly affects the final position of the pollutant centroid. By analyzing the model uncertainties, this study reveals the key factors influencing the drift of fish-feed pollutants. This information is crucial for aquaculture vessels in planning routes, considering environmental factors, and reducing potential pollution risks.

Large Scale Turbulent Round Free Jet Far Field Investigations Using Shake-The-Box 3D Lagrangian Particle Tracking

In this study, we utilize the Shake-The-Box (STB) Lagrangian Particle Tracking (LPT) algorithm to conduct large-scale measurements in the far field of a turbulent jet. We confirm self-similar mean velocity and Reynold stress profiles across two fields of view (FOVs) spanning 90 to 240 nozzle diameters in streamwise direction. Furthermore, the utilization of a novel version of the data assimilation scheme FlowFit enables the visualization of instantaneous realizations of coherent structures in terms of Q-values. The results indicate that the structures are predominantly tube rather than hairpin-like. The high number of tracked particles and the extensive measurement range allow for the estimation of mean dissipation as a function of the distance from the nozzle using structure functions. A comparison of results derived from longitudinal and transverse approaches with those obtained using the velocity-acceleration structure function indicates that the latter provides more accurate results due to its validity in anisotropic flows. However, the findings also indicate that the anisotropy diminishes downstream. The determination of mean dissipation and acceleration enables the investigation of the validity of the Heisenberg-Yaglom relation in this anisotropic flow. Nevertheless, acceleration is a highly intermittent value, which hinders capturing all relevant events to measure its variance accurately. This paper presents the difficulties encountered in the tracking and filtering of the trajectories, offering a perspective on potential future solutions to the problem.

Dynamic Wall Shear Stress Measurement Using Event-Based 3D Particle Tracking

We describe the implementation of a 3d Lagrangian particle tracking (LPT) system based on event-based vision (EBV) sensors and demonstrate its application for the near-wall characterization of a turbulent boundary layer (TBL) in air. The viscous sublayer of the TBL is illuminated by a thin light sheet that grazes the surface of a glass window inserted into the flat wall of the wind tunnel wall. The data simultaneously captured by three synchronized EBV-cameras is used to reconstruct the 3d particle tracks within 0.4 mm of the wall on a field of view of 12.0 mm by 7.5 mm. The velocity and position of particles within the viscous sub-layer permit the estimation of the local, unsteady wall shear stress vector under the assumption of linearity between particle velocity and wall shear stress. Thereby, 2d distributions and higher order statistics of the unsteady wall shear stress are obtained. The systematic underestimation of the spanwise shear stress fluctuation can be explained on the basis of DNS data; a methodology for its mitigation is proposed. The employed EBV hardware coupled with suited LPT algorithms provide data quality on par with currently used, considerably more expensive, high-speed framing cameras.

The role of 3D electrostatic field in modeling the electrospinning process

Electrospinning is a cost-effective but very intricate method of producing polymeric nanofibers at room temperature. Unfortunately however, it is extremely difficult to predict the diameter or other properties of the fibers produced via electrospinning a prior. In this paper, we present a new approach to simulate fiber formation during electrospinning. Our work builds on the mathematical framework that was originally developed by Reneker and Yarin in 2000. Our approach incorporates the 3D electrostatic field that surrounds the fiber in a Lagrangian discrete particle tracking algorithm that tracks the trajectory of the fiber in air and predicts its deposition velocity and diameter. We investigate the effects of electrostatic field spatial variation on fiber electrospinning and compare our results with those obtained using a constant electrostatic field, the traditional approach, and with experiments (conducted using polyurethane). We considered three different electrospinning configurations of single-needle-plate-collector, single-needle-drum-collector, and two-needles-drum-collector to investigate how different electrostatic fields impact fiber formation. The computational model developed in this work helps to advance the current state of the art in modeling the electrospinning process.

Three-Dimensional Quantitative Flow Visualization Around a Thrust Reverser

Volumetric particle tracking velocimetry measurements are performed in a low-speed wind tunnel to study the flow around a 1:12-scale aircraft model with jet engines operating with thrust reversers. The engine jet and freestream flow velocity are varied to yield a jet to freestream velocity ratio of ranging from 1.5 to 6. Measurements at such scale () require the use of strongly scattering helium-filled soap bubbles as flow tracers, which are introduced in both the jet and the freestream flow. The tracer’s three-dimensional motion is determined using an array of cameras and a Lagrangian particle tracking algorithm. The mean velocity field reveals the jet inner structure as well as its interaction with the freestream, the ground board, the nacelle, the fuselage, and the horizontal and vertical tails. The experiments allow detection of exhaust reingestion as well as the aerodynamic interference with control surfaces at the tail segments in a single measurement volume. The results are in good agreement with conventional temperature rake measurements while adding details of the flow topology and of the large-scale unsteady flow fluctuations. Finally, the jet reversal characteristics with varying freestreams and nozzle pressure ratios are assessed, demonstrating the feasibility and versatility of volumetric velocimetry measurements for industrial aerodynamics.

Analysis of multiple successive collisions between a prolate spheroidal particle and a plane wall

This study investigates multiple successive collisions between elastic prolate spheroid particles and a rigid planar wall in vacuum. The influence of various factors on multiple particle–wall collisions, including the particle aspect ratio, orientation angle, impact velocity, material properties, size, impact angular velocity, and wall friction coefficient, is analyzed. The results show that secondary and tertiary collisions are primarily determined by the particle aspect ratio and orientation angle. Four particle aspect ratios (λ=1.5, 2, 3, and 5) are investigated. A secondary collision occurs for λ=2 to 5. For λ=5, the particle can collide with the wall three times in a row. The corresponding ranges of the particle orientation angles for the secondary and tertiary collisions are provided for different particle aspect ratios. The maximum elastic force acting on the particles during each collision was also analyzed. The proposed model is verified to be applicable to gas-driven particles, and an example of its implementation within a Lagrangian particle-tracking algorithm is provided.

Numerical investigation of the three-dimensional paths of plastic polymers in the Gulf of Naples

The high-resolution Campania Regional Ocean Model (CROM), coupled with an online Lagrangian particle tracking algorithm, is used to investigate the horizontal and vertical behavior of different (in terms of size and density) plastic polymer types during February and August 2016 in the Gulf of Naples. The transport of passive particles is evaluated based on the three-dimensional Eulerian velocity fields provided by the ocean model. The virtual particles are released in several hot spot areas in the Gulf of Naples where most of the marine debris is supposed to come from. A sensitivity analysis on the vertical sinking for negatively buoyant particles is carried out. The sinking behavior is determined by the settling velocity, which depends on the physical properties of the individual litter item as well as on the hydrodynamical features of the marine environment. Different numerical experiments are carried out to evaluate the effect of marine dynamics on three-dimensional transport.

Investigation of turbulent superstructures in Rayleigh–Bénard convection by Lagrangian particle tracking of fluorescent microspheres

We present spatially and temporally resolved velocity and acceleration measurements of turbulent Rayleigh–Bénard convection (RBC) in the entire fluid sample of square horizontal cross section with length L=320 mm and height H=20 mm, resulting in an aspect ratio of Gamma =H/L=16. The working fluid was water with a Prandtl number of Pr=7 and the Rayleigh number was set to {text{Ra}}= 1.1times 10^6. In order to minimize surface reflections, we used fluorescent polyethylene microspheres as tracer particles that were imaged at a rate of 19 Hz by six cameras. From the images, the particle positions, velocities, and accelerations were determined via the ‘Shake-The-Box’ (STB) Lagrangian particle tracking algorithm. With this approach, we could simultaneously track more than 300,000 particles and hence study the resulting turbulent structures in the Eulerian and Lagrangian frames while resolving the smallest spatial and temporal scales of the flow.

Dynamics Of Coherent Structures In 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 Rayleigh-Bénard convection in a cylindrical sample with aspect ratio one. Using the "Shake-The-Box" Lagrangian Particle Tracking algorithm, we were able to instantaneously track more than 560,000 particles in the complete sample volume (~ 1 m³), corresponding to mean inter-particle distances of less than 8 volume averaged Kolmogorov lengths. We used the data assimilation scheme "FlowFit" with continuity and Navier-Stokes-constraints to regularize the scattered velocity and acceleration data via continuous 3D B-Splines on a cubic grid to recover the smallest flow scales. The measurements were enabled by a dedicated bubble fluid solution, which we developed for generation of long-lived helium filled soap bubbles, allowing for long-term optical flow measurements at large scales in gaseous media. We show visualizations of the Large-Scale Circulation (LSC) using iso-surfaces the Q-criterion, that allow a glance into the turbulent structure of the flow and to spot some of the dynamic features of the LSC. By employing Proper Orthogonal Decomposition (POD) in the rotating frame of the LSC, we are able to model the oscillatory dynamics of the LSC using just the first three POD modes with a standard deviation from the full data set of less than 5 % utilizing only ~50% of the turbulent kinetic energy.

Investigation Of Turbulent Superstructures In Rayleigh-Benard Convection By Lagrangian Particle Tracking Of Fluorescent Microspheres

We present spatially and temporally resolved velocity measurements of turbulent Rayleigh-Bénard convection (RBC) in a fluid sample of square horizontal cross section with length L = 320 mm and height H = 20 mm, resulting in an aspect ratio of Γ = H/L = 16. The working fluid was water with a Prandtl number of Pr=7 and the Rayleigh-number was set to Ra = 1.1 × 10^6. We seeded the flow with fluorescent polyethylene microspheres that were photographed at a rate of 19 Hz by six cameras. From the images the particle position and their velocity was calculated via the "Shake-The-Box" (STB) Lagrangian particle tracking algorithm. With this approach, we could simultaneously track more than 300,000 particles and hence study the resulting turbulent structures in the Eulerian and Lagrangian frames.

Measurements Of The Energy Dissipation Rate In Homogeneous Turbulence Using Dense 3D Lagrangian Particle Tracking And FlowFit

We present measurements of the full velocity gradient tensor and all volumetric dissipation rate elements based on dense fields of fluid particle trajectories in homogeneous turbulence at Re_λ~270 and ~370 in a Kármán flow between two counter-rotating disks with impellers. Applying the Shake-The-Box (STB) Lagrangian Particle Tracking (LPT) algorithm, we are able to instantaneously track up to 80.000 particles in a volume of 40 x 40 x 15 mm³. The mean interparticle distance is lower than 7 Kolmogorov lengths for the Re_λ ~270 case. A data assimilation scheme (FlowFit) with continuity and Navier-Stokes- constraints is used to interpolate the scattered velocity and acceleration data by a continuous 3D B-Spline representation, enabling to recover (locally) the smallest flow scales. In the presentation, we show Lagrangian velocity and acceleration statistics, as well as the Eulerian counterparts on velocity gradients and pressure fields. We compute the energy dissipation rate directly by making use of quadruples of particle trajectories in close proximity (r < 3η) and compare it to indirect approaches using second-order velocity- and velocityacceleration structure functions in the inertial subrange.

A Web Portal For Automatic Performance Evaluation Of Lagrangian Particle Tracking And Data Assimilation Algorithms

We introduce a web portal dedicated to benchmarking Lagrangian Particle Tracking (LPT) and Data Assimilation (DA) processing algorithms. LPT is here understood in a wide sense, as we consider acquisition situations ranging from only two illuminations (i.e. Particle Tracking Velocimetry - PTV) to a large number of images. The website, https://www.onera.fr/en/flow-benchmarks allows not only to download datasets, but also to upload results and automatically obtain their performance evaluation; in its principle, it is thus similar to a number of already existing benchmark websites in the computer vision community, while none existed so far in the community of optical metrology for fluid mechanics. On the basis of the obtained performance, a user has the choice to publish their results or not on the public page of the dataset. The present work presents the website structure, its rules for participation, and a description of the first dataset available at opening, namely the two-pulse (PTV) case of the First LPT and DA Challenge dataset (Sciacchitano et al. 2021).

Main Results Of The Analysis Of The HOMER Lagrangian Particle Tracking And Data Assimilation Database

In this work, we extend the analysis of Lagrangian Particle Tracking (LPT) and Data Assimilation (DA) algorithms, presented at the ISPIV21 conference, to the case of a turbulent wall-bounded flow interacting with a moving panel. The work is conducted within the European project HOMER and the data is processed by the partners of the project consortium. A synthetic experiment is performed that reproduces the air flow around a cylinder in ground effect, whereby a flexible panel is placed undergoing periodic oscillations. The database comprises two different panel's materials, namely metal and rubber, different marker densities on the panel’s surface and different concentrations of tracer particles in the flow. Images of the flow tracers and of the surface markers are acquired either with a four-camera volumetric imaging setup or with a dual setup composed of four LPT cameras and two Digital Image Correlation (DIC) cameras. Additionally, three image acquisition modes are simulated, namely time-resolved, two-pulse and four-pulse. The data are analyzed in terms of percentages of correctly reconstructed, missed and ghost particles, errors of the measured particles’ positions, velocities and accelerations (LPT analysis) and errors of the reconstructed flow fields, panel’s positions and surface pressures (DA analysis).

Large-scale volumetric flow studies on transport of aerosol particles using a breathing human model with and without face protections

Exhalation of small aerosol particle droplets and their airborne transport, dispersion, and (local) accumulation in closed rooms have been identified as the main pathways for direct and indirect respiratory virus transmission from person to person, for example, for severe acute respiratory syndrome coronavirus-2 or measles. Therefore, understanding airborne transport mechanisms of aerosol particles inside closed populated rooms is an important key factor for assessing and optimizing various mitigation strategies. Unsteady flow features, which are typically evolving in such mixed convection flow scenarios, govern the respective particle transport properties. Experimental and numerical methods that enable capturing the related broad range of scales in such internal flows over many cubic meters in order to provide reliable data for the adaptation of proper mitigation measures (distances, masks, shields, air purifiers, ventilation systems, etc.) are required. In the present work, we show results of a large-scale, three-dimensional Lagrangian particle tracking (LPT) experiment, which has been performed in a 12-m3 generic test room capturing up to 3 × 106 long-lived and nearly neutrally buoyant helium-filled soap bubbles (HFSBs) with a mean diameter of dHFSB ∼370 μm as (almost) passive tracers. HFSBs are used as fluid mechanical replacements for small aerosol particles dP < 5 μm, which allow to resolve the Lagrangian transport properties and related unsteady flow field inside the whole room around a cyclically breathing thermal manikin with and without mouth-nose-masks and shields applied. Six high-resolution complementary metal-oxide semiconductor streaming cameras, a large array of powerful pulsed light emitting diodes, and the variable-time step Shake-The-Box LPT algorithm have 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 a seated and breathing human model.

An analytical approach for urban groundwater transit time distributions accounting for the effect of stormwater infiltration system

The stormwater infiltration system (SIS) has been recognized as a feasible way to manage stormwater and restore streamflow. As a lumped representation of the flow and transport processes, the groundwater transit time distribution (TTD) is highly relevant to this restoration goal. However, the influence of the SIS on groundwater TTDs has rarely been studied. In this paper, we propose a novel analytical model for groundwater TTDs in regional urban aquifers accounting for the impact of the SIS. This analytical solution is developed for a homogeneous 2-D cross-section of an idealized unconfined aquifer following the Dupuit-Forchheimer assumption. The analytical solution is verified through the comparison with simulated TTDs using the Lagrangian particle tracking algorithm. The global sensitivity analysis reveals that the stormwater infiltration rate, the number of infiltration facilities, the size of the urban area, and the evapotranspiration are the most important factors for groundwater mean transit times (MTTs). Although groundwater discharge and MTT can be restored to the pre-urban one, groundwater TTDs will inevitably deviate from the pre-urban ones due to the alteration from diffuse recharge to infiltration-focused recharge, indicating that the urban groundwater flow regime cannot be fully restored to the pre-urban conditions. Overall, as a first-order approximation of the real-world urban groundwater system, the proposed analytical model provides decision-making support for urban water resources management and the design of the SIS.

A decade of modeled dispersal of Dungeness crab Cancer magister larvae in the California Current

Marine populations are often typified by large annual variations in the number of larvae that return to the adult population. The Dungeness crab Cancer (Metacarcinus) magister is an important economic and ecological species along the western seaboard of the continental USA. Research suggests larval returns of Dungeness crabs vary annually by a factor of 1000, strongly influencing the population dynamics of the species. To understand how hydrographic conditions affect population dynamics, a light trap in Coos Bay, Oregon, was monitored daily during the recruitment season (April to September) from 1997 to 2001 and from 2006 to the present. Using an individual-based biophysical model, we tested the hypothesis that more Dungeness crab larvae recruit during negative-phase Pacific Decadal Oscillation (PDO). The model uses the Regional Oceanic Modeling System to simulate circulation in the California Current and an offline Lagrangian particle-tracking algorithm (Larval TRANSport Lagrangian Model, LTRANS) to model larval dispersal. We validated our model by comparing the model data to the light trap data. Our findings support the hypothesis that more megalopae (pelagic postlarvae) recruit during the negative phase of the PDO. In addition, megalopae appear to spend longer in the water column during positive-phase PDO as a result of faster development rates likely due to warmer seawater temperature. Lastly, our model suggests that the population experiences more self-recruitment than previously thought, albeit not to an extent to suggest there are multiple metapopulations.

Image-based operational modal analysis and damage detection validated in an instrumented small-scale steel frame structure

The use of image-based techniques in structural dynamics is constantly growing thanks to the decrease in the cost of high-speed cameras and the improvement in image processing algorithms. Compared to traditional sensors, such as accelerometers or velocimeters, the use of fast cameras for data acquisition allows the number of measurements points to be significantly increased. However, such an abundance of points, not always lead to an increased accuracy of damage detection algorithms. With this in mind, we compare different damage detection techniques by using displacement data and modal quantities. A small scale steel frame structure is used to validate the damage detection by using measurements acquired through a high-speed camera with different image processing techniques. The Hybrid Lagrangian Particle Tracking (HLPT) algorithm and Digital Image Correlation (DIC) are both used to extract displacement measurements from images. The results are compared with those obtained with seismic class accelerometers which are normally used in the lab for such an application. Damage localization and intensity have been determined through image-based measurements without losing the accuracy obtained with accelerometers.

Aeroelastic Characterization of a Flexible Wing Using Particle Tracking Velocimetry Measurements

The aerodynamic, elastic, and inertial components in Collar’s triangle of forces acting on a flexible wing with span width and chord are determined based on integrated optical measurements of the structural and aerodynamic response to steady and unsteady periodic inflow conditions at a chord-based Reynolds number of . The measurement device is a coaxial volumetric velocimeter mounted on a robotic arm, which is used to perform optical measurements of fiducial markers on the wing surface, and helium-filled soap bubbles, which are used as flow tracers. The optical measurements of the structural markers and the flow tracers are both processed with the Lagrangian particle tracking algorithm Shake-the-Box. Subsequently, physical models are used to determine the inertial and elastic forces of the aeroelastic interaction from the marker tracking results, and to determine the unsteady aerodynamic lift force from the flow velocity fields. The results of this integrated aeroelastic characterization approach are in physical agreement with each other according to the equilibrium of forces in Collar’s triangle and good agreement with external reference measurements.

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

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.

Lagrangian Particle Tracking: a link between localization error and fraction of missed particles

This paper aims at analysing the behaviour of particle localisation error in 3D Lagrangian Particle Tracking (LPT) techniques, with a particular emphasis on general properties, independent of a specific algorithm. Based on the hypothesis that in LPT algorithms, errors on the image formation models are solely due to random noise, we show/prove the existence of a best achievable root mean square error (RMSE) on particle localisation, that, for a setup at a given seeding density, depends only on the noise level. We provide a procedure to estimate this lower bound, and show that it can only be reached if there are no missed detections; further on, we establish a link between localisation error and fraction of missed particles. We illustrate the consistency of this model on the results of the recent First Challenge on LPT (see ISPIV21 papers by Leclaire et al. and Sciacchitano et al.)