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Papers
61,005 resultsShowing papers similar to A physics-based and orientation-aware method for the direct calculation of the settling speed of prolate spheroidal particles in the atmosphere : theoretical basis and comparison to laboratory and CFL data
ClearGravitational settling of microplastic fibers: experimental results and implications for global transport
This study measured the gravitational settling velocities of microplastic fibers and found that their non-spherical shape causes them to settle much more slowly than spheres of the same volume. Current atmospheric transport models that assume spherical particles significantly underestimate how long fibers remain airborne. These results have important implications for predicting how far microplastic fibers can travel before depositing.
Effects of Shape and Size on Microplastic Atmospheric Settling Velocity
Researchers measured atmospheric settling and horizontal drift velocities of various microplastic shapes and sizes in controlled settling chambers, providing empirical data needed to improve atmospheric transport models that explain how microplastics reach remote environments.
The atmospheric settling of commercially sold microplastics
Researchers measured the gravitational settling velocities of commercially available glitter microplastics (0.1-3 mm nominal diameter) and synthetic fibers (1.2-5 mm length) in air, finding that non-spherical shapes cause complex settling behaviors that deviate substantially from spherical particle models used in atmospheric transport models.
Atmospheric transport of microplastic particles as a function of their size and shape
Researchers investigated the atmospheric transport and settling of microplastic particles as a function of size and shape, implementing a shape-correction parameterization for fiber-shaped particles in an atmospheric transport model to better represent their reduced gravitational settling velocity compared to spheres. The study showed that non-spherical fibers experience greater atmospheric drag, increasing their residence time and transport distance, and that including shape effects improved agreement between model output and ground-based measurements.
Low Reynolds Number Settling of Cylindrical Rods with Various Geometries in a Quiescent Fluid
Researchers experimentally investigated the settling behaviour of curved, V-shaped, U-shaped, and S-shaped cylindrical rods at low Reynolds numbers to improve models of atmospheric microplastic fibre transport, conducting experiments with millimeter-scale metal rods spanning aspect ratios from 10 to 120. The study found that fibre geometry significantly affects settling trajectories and drag compared to simplified sphere or straight-cylinder approximations used in current atmospheric transport models.
Modeling the Gravitational Settling of Microplastic Fibers in the Atmosphere
Researchers developed and applied a model for gravitational settling of microplastic fibers in the atmosphere, examining how fiber shape and size influence atmospheric residence time and deposition patterns to better understand the global atmospheric transport cycle of microplastics.
Terminal Settling Velocity of Cylindrical Rods with Various Geometries Applicable to Atmospheric Microplastics
Researchers measured how the shape of cylindrical microplastic fibers affects their settling speed through air, finding that curved and V-shaped fibers fall significantly faster than straight ones — up to 57% faster for V-shaped rods — which matters for predicting how airborne microplastics disperse in the atmosphere.
Improved Settling Velocity for Microplastic Fibers: A New Shape-Dependent Drag Model
A new shape-dependent drag model was developed to improve the accuracy of settling velocity predictions for microplastic fibers, addressing a major limitation of existing drag models that significantly underpredict fiber settling in aquatic environments.
Microfiber behavior in turbulence and in quiescent conditions: insights from 3D high-speed measurements
Researchers investigated the settling dynamics of microplastic fibers with high aspect ratios under turbulent and quiescent airflow conditions, using 3D high-speed measurements to show that existing drag models fail to accurately predict settling velocities of these anisotropic curved fibers with diameters of 10-100 micrometers.
Long-distance atmospheric transport of microplastic fibers depends on their shapes
Researchers developed a theory-based settling velocity model for microplastic fibers in the atmosphere that accounts for fiber shape and cross-sectional dimensions, finding that correctly characterising flat fibers rather than treating them as cylinders increases estimated mean atmospheric residence time by over 450%, suggesting the ocean is a major source of airborne plastic and that long-range transport is far more efficient than previously thought.
Twist, turn and encounter: the trajectories of small atmospheric particles unravelled
Experiments and simulations studied how non-spherical solid particles (including microplastics) settle through air, finding unexpectedly complex tumbling and spiraling trajectories even at low speeds. These insights improve predictions of how airborne microplastic particles travel and deposit across landscapes.
Torques on curved atmospheric fibres
Researchers derived a theoretical model for how planar curved atmospheric fibers settle in quiescent air, finding that fluid-inertia torques can align asymmetric fibers at oblique angles relative to gravity — consistent with recent laboratory observations. The model demonstrates that inertial alignment is a general and important factor governing the atmospheric transport of asymmetric particles such as curved microplastic fibers and ash particles.
Settling velocity of microplastic particles having regular and irregular shapes
Researchers measured how quickly microplastic particles of various shapes settle through water, testing 66 different particle types including spheres, cylinders, fibers, and irregular fragments. They found that particle shape significantly affects settling speed, with fibers and flat shapes sinking more slowly than spheres of the same size. The study provides new equations for predicting where microplastics end up in oceans and waterways based on their shape.
Experimental investigation of the fallout dynamics of microplastic fragments in wind tunnel: The BURNIA agenda
Wind tunnel experiments were used to measure the settling velocity of airborne microplastic fragments of PET, PVC, and low-density polyethylene, providing the first empirical data to model how plastic particles fall out of the atmosphere.
Settling of nonuniform cylinders at intermediate Reynolds numbers
This study investigated the settling behavior of non-uniform cylindrical particles at intermediate Reynolds numbers, providing new data on how particle shape and aspect ratio influence drag and settling velocity. The findings are relevant to predicting the transport and deposition of microplastic fibers in water.
Coupled CFD-DEM modelling to assess settlement velocity and drag coefficient of microplastics
Researchers used computational fluid dynamics coupled with particle simulations to model how the size, shape, and density of microplastics affect their settling velocity and drag in water. Accurate physical models of microplastic behavior are essential for predicting where particles accumulate in rivers, lakes, and the ocean.
Normalized Settling Velocity Governs Short-Range Transport of Atmospheric Microplastics
Wind tunnel experiments showed that how fast a microplastic particle settles under gravity—its normalized settling velocity—is the single best predictor of how far it travels through the air before landing. This finding helps fill a major gap in atmospheric microplastic research by enabling better models of where airborne plastic particles deposit, which affects estimates of human inhalation exposure and ecosystem contamination.
Towards better predicting the settling velocity of film-shaped microplastics based on experiment and simulation data
Researchers combined experimental and simulation data to better predict how film-shaped microplastics settle through water, since most existing models are based on spherical particles. They found that the particle definition approach was more suitable than equivalent spherical diameter for characterizing flat, irregular microplastics. The improved settling velocity predictions could help scientists better understand how film-shaped microplastics travel and accumulate in aquatic environments.
A new model for the terminal settling velocity of microplastics
A new empirical model for the terminal settling velocity of microplastics was developed and validated using 1,343 experimental measurements covering a range of particle shapes and materials. The model improves predictions of microplastic sedimentation rates, which are critical for understanding how plastic particles are transported and deposited in water bodies.
Lagrangian tracking of particles settling through the atmosphere: influence of particle shape on its dispersion
Researchers launched instrumented balloon experiments as part of the IMPACT field campaign in northern Finland to track non-spherical particle settling through the atmosphere, finding that particle shape significantly influences dispersion trajectories and that existing spherical-particle models underestimate the spread of realistic atmospheric particles such as microplastics.
Empirical Shape-Based Estimation of Settling Microplastic Particles Drag Coefficient
This study experimentally measured the settling behavior of flat square microplastic particles in water, finding that shape significantly affects sinking speed and drag compared to spherical particles. Understanding how microplastic shapes influence settling is essential for modeling where plastics accumulate in rivers and ocean sediments.
Modeling Microplastic Transport in the Marine Environment: Testing Empirical Models of Particle Terminal Sinking Velocity for Irregularly Shaped Particles
Researchers tested multiple drag models for predicting the terminal settling velocity of irregularly shaped microplastic particles in seawater, identifying three high-precision models and demonstrating that settling velocity is largely stable across ocean depths and independent of initial particle velocity, improving the accuracy of marine microplastic transport simulations.
Settling processes of cylindrical microplastics in quiescent water: A fully resolved numerical simulation study
Using a lattice Boltzmann numerical model, this study simulated how cylindrical microplastic fibers sink through still water and identified a critical shape ratio (aspect ratio ~0.93–0.94) at which settling behavior shifts dramatically. Understanding how fiber shape governs sinking speed is key to predicting where MP fibers accumulate in aquatic environments and how long they remain suspended.
Systematic Evaluation of Physical Parameters Affecting the Terminal Settling Velocity of Microplastic Particles in Lakes Using CFD
Researchers used computational fluid dynamics to systematically evaluate how physical parameters including size, shape, density, and surface roughness affect microplastic settling velocity in lakes, finding that particle shape and density are the most influential factors determining residence time.