Transport Of Suspended Particles Research Articles

Temperature-driven coupled transport of pollutants and suspended particles established by granular thermodynamics

The temperature-driven effects on pollutant transport are significant, including thermal diffusion of pollutants, thermal osmosis of solutions, thermal motion of suspended particles, and other deformation and transformation processes. The pollutant seepage field equation was derived based on granular thermodynamics, and the motion equation of suspended particles was derived from Newton's second law. A comprehensive coupled transport model for the two-phase flow of pollutants and suspended particles in saturated porous media was established, which can effectively consider the impact of temperature driving. The model accurately described the coupled transport process of pollutants and suspended particles under different temperatures and particle sizes during single-pulse injection. Furthermore, the application of this model in natural clay layers under varying temperature gradients was discussed. The results indicated that, for the same time, an increase in temperature at the high-temperature end led to a 36.5 % decrease in the peak concentration of pollutant transport. When the temperature difference was significant, thermal osmosis and thermal motion were the main mechanisms for the coupled transport of pollutants and suspended particles, with the diffusion mechanism induced by concentration and temperature gradients not dominating. Thermal diffusion positively drove the transport of pollutants, while thermal osmosis and thermal motion under temperature gradients had a reverse inhibitory effect on pollutant transport.

Modeling of multi-fractional suspended particle pathways in a shallow water basin under influence of strong winds

In this study, we investigate the complex dynamics of multi-fractional suspended particle transport in a shallow water basin subjected to strong wind conditions. Our research focuses on understanding the interplay between wind-induced advection and particle settlement, and its implications for sediment redistribution.Through our analysis, we reveal the distinct behaviors of different sediment fractions. Clay particles, constituting the lowest fraction in sediment cores, remain suspended throughout the simulation due to their low settlement velocity, with relatively stable concentrations. Conversely, the dominant fraction, medium silt, is suspended during intense wind events but quickly settles to the bed due to its higher settling velocity. Wind stress exceeding 0.05 Pa triggers particulate matter erosion, leading to its presence in the water column.Additionally, we explore the 2D distribution of sediment characteristics, including thickness, dry density, and mud fraction, to identify areas prone to erosion and deposition. Our findings demonstrate that coastal areas of the Taganrog Bay experienced significant erosion following strong wind events, exhibiting the thinnest sediment thickness and the highest dry bulk density. Deposition areas, characterized by thicker sediment layers and lower dry density, were often found in proximity to erosion zones, indicating the influence of particle resuspension and settlement processes.Furthermore, we analyze the implications of our findings on the vulnerability of specific regions to erosion and deposition. The central part of the sea contains moderately thicker sediment layers with a moderately high mud fraction, representing a zone of fine sediment accumulation. These fine sediments, including fine silt and clay, remain suspended for longer durations and are redistributed over greater distances by currents.Overall, our study provides valuable understanding into the multi-fractional suspended particle pathways and their interaction with strong winds in shallow water basins. The results contribute to a better understanding of sediment dynamics, which has implications for coastal management, environmental monitoring, and the preservation of benthic ecosystems.

Analysis of environmental transport of suspended sediment particles in a tidal wetland flow under the effect of floating vegetation absorption

Wetlands play an important role in maintaining many natural cycles and supporting a wide range of biodiversity. In the current world, the transport of solute in a wetland with vegetation is an essential issue in environmental, biological, geophysical, and concerned applications. Specially, floating vegetated wetland which is a buoyant platform enveloped by plants, playing a pivotal role in filtering and purifying water in aquatic ecosystems The main focus of the present research is to investigate the transport of sediment particles in a depth-dominated tidal floating vegetated wetland (FVW) flow. The characteristics of floating vegetation absorption and vegetation parameter in FVW are explained to explore the transport of sediment particles. This work’s model relies on an advection-diffusion equation, the solution of which discloses the concentration of settling particles in the water phase. Utilizing the method of moments, a set of moment equations is derived from the governing equation. The equations of moment are then solved using a finite difference implicit scheme. Further, the four moments and Hermite polynomial illustration is adopted to derive the vertical mean concentration distribution profile. The effective dispersivity and the concentration distributions of the sediment particles are illustrated for three different situations of fluid flow: steady, purely oscillatory, and periodic flow with non-zero-mean for all time. The effects of the vegetation factor, settling velocity, absorption due to floating vegetation, and other important factors on sediment transport in FVW are discussed for three different cases separately. Result shows as settling velocity (ω) increases, the influence of vegetation absorption (β) on dispersion coefficient diminishes in the steady state, and its effect on mean concentration becomes less pronounced due to the downward movement of particles. This is because vegetation absorption is stronger near the upper surface, but higher ω values lead to particle downward, reducing β′s impact. The results are described in the context of some real-world situations, as the free surface of a tidal wetland is naturally covered with plants; FVW serve as a natural water purification filter for polluted estuaries, contaminated crude oil wastewater, and so on. This study has potential to aid in water purification efforts as well as for the protection and conservation of coastal environments to limit sea level rise.

Numerical Investigation of the Two-Component Suspension Filtration in a Porous Medium Taking into Account Changes in the Characteristics of the Porous Medium

The paper explores a mathematical model of the filtration of dual-component suspension within a porous medium characterized by two distinct zones. This model encompasses mass balance equations of suspended particles, kinetic equations of deposition formation for both reversible and irreversible deposition types for each suspension component, and incorporates Darcy’s law. In order to solve the problem, we formulate a numerical algorithm for computer-based experimentation on the basis of the finite difference method. Through the analysis of numerical findings, we establish key features of two component suspension filtration within a porous medium. Furthermore, we examine the effects of model parameters on the transport and deposition of suspended particles in a two-component suspension within porous media. The polydispersity of the suspension and the multi-stage nature of deposition kinetics can induce effects that differ from those typically observed in the transport of onecomponent suspensions with single-stage particle deposition kinetics.

From cave to spring: Understanding transport of suspended sediment particles in a fully phreatic karst conduit using particle analysis and geochemical methods

AbstractKarst aquifers are vulnerable to contamination, especially in the context of heavy rainfall events. Contamination is often associated with turbidity that can originate from the soil zone, infiltrating surface waters or resuspension of previously deposited sediments within the aquifer. While turbidity events can be well monitored at karst springs, related information about the sediment origin and the spatiotemporal input function usually remain unknown. Thus, the mobility and attenuation of the particulate matter and associated pollutants can hardly be determined quantitatively. A tracer test with suspended cave sediments and solute tracers for comparison has hence been performed in a karst aquifer at the Blue Spring (Blautopf) in Southern Germany. The tracers were injected in the cave system, at the beginning of a fully phreatic karst conduit, and monitored at the spring after a travel distance of 1250 m. The particle‐size distribution was monitored using a particle counter and sediment samples were filtered with 0.45‐μm cellulose acetate filters. Particles on the filter were analysed for major and trace elements as well as rare earth elements (REE) by ICP‐MS after acid digestion. Results show that (1) sediment particles were transported faster than solutes, which was interpreted as a transport in the main flow path of the conduit, whereas conservative tracers tend to diffuse into smaller fissures as well. (2) All measured particles sizes were transported at similar flow velocities. (3) A transport associated to sediment particles could be shown for all measured elements. This study presents a methodological improvement of comparative sediment tracer tests as well as deeper insights into particle and element transport processes in karst aquifers, originating from previously deposited cave sediment. Results provide deeper knowledge into transport processes of sediment‐associated contaminants, such as heavy metals which may strongly be affected by the particle size. This knowledge contributes to a better management of karst water resources in the context of turbidity events.

Laboratory Studies on the Influence of Ionic Strength on Particle Transport Behavior in a Saturated Porous Medium

An experimental study has been undertaken to investigate the effect of flow velocity and ionic strength on the transport of suspended particles (SP) and their deposition in a saturated porous medium. The SP injections were carried out using a laboratory column filled with sand and a pulse injection method. Ionic strengths varying between 0 and 600 mM (NaCl) have prospected. Two velocities were tested: 0.15 and 0.30 cm/s. Selected polydisperse particles diameters ranging from 0.27 to 5 μm and a median diameter (dp50) equal to 2.25 μm were used. An analytical solution of the convection–dispersion equation with first-order deposition kinetics was used to describe the experimental breakthrough curves and to identify the transport parameters. The results show that the increase of ionic strength promotes the retention of the SP in the porous medium. In addition, retention is more important when the flow velocity is low. The deposition kinetics coefficient increases with increasing ionic strength and flow velocity.

Position-dependent rates of film growth in drying colloidal suspensions on tilted air-water interfaces.

Suspended particles in a solvent form a packed film when the solvent evaporates. We investigated film growth rates in a narrow channel on a tilted drying interface and observed clear differences in the rates of film growth. Films grew faster at one end and slower at the other; thus, the slope of the packing front, i.e., the boundary between the packed film and the drying suspension, changed as drying proceeded. However, the difference in film growth rates became smaller as the slope of the packing front changed and the rates of film growth at the either end ultimately became identical. We found that the differences in the rates of film growth were proportional to cosθ, where θ is the angle defined by the slope of the packing front. We constructed a mathematical description to successfully express the time evolution of both the difference in the growth rates and the packing front angle θ. Relationships between drying-induced flow of bulk suspensions and transport of suspended particles to the tilted packing front are discussed.

Численное моделирование распространения микропластика в прибрежной зоне водоема вследствие волнового движения

The transport of suspended microplastic particles in an aqueous medium is closely related to hydrodynamic circulation. There are several mechanisms of horizontal and vertical movement of suspended microplastic particles associated with their concentration. In the article, a model describing the change in the concentration of suspended microplastic particles is considered, discretization is carried out, and the results of numerical experiments in two-dimensional and three-dimensional cases are obtained. The results of both the analytical model and numerical simulation demonstrate that waves can affect the distribution of floating particles near a free surface. The results of numerical simulation are largely consistent with the theory.

Mathematical model of process of sedimentation of multicomponent suspension on the bottom and changes in the composition of bottom materials

The paper considers 2D and 3D models of transport of suspended particles, taking into account the following factors: movement of aqueous medium; variable density depending on the suspension concentration; multicomponent character of suspension; changes in bottom geometry as a result of suspension sedimentation. The approximation of the three-dimensional diffusion-convection equation is based on splitting schemes into two-dimensional and one-dimensional problems. In this work, we use discrete analogues of convective and diffusion transfer operators in the case of partial cell occupancy. The geometry of the computational domain is described based on the occupancy function. The difference scheme used is a linear combination of the Upwind and Standard Leapfrog difference schemes with weight coefficients obtained by minimizing the approximation error. This scheme is designed to solve the problem of impurity transfer at large grid Peclet numbers. Based on the results of numerical experiments, conclusions are drawn about the advantage of the 3D model of multicomponent suspension transport in comparison with the 2D model. Computational experiments have been performed to simulate the process of sedimentation of a multicomponent suspension, as well as its effect on the bottom topography and changes in its composition.

Spatial Variations in Microfiber Transport in a Transnational River Basin

Five countries share the catchment of the Tisza River (Central Europe). In most households electricity and water are available, and by washing synthetic clothes they can produce a large number of microfibers. However, in many sub-catchments of the river, the wastewater treatment is insufficient; therefore, microplastics (MP), especially plastic microfiber emissions into rivers, represent a problem. Our goal was to analyze the suspended sediment and microfiber transport at the low stage, making repeated (2021 and 2022) measurements in the Tisza River (946 km) at 26 sites across three countries. Water sampling was performed by pumping 1 m3 of water through sieves (90–200 µm). The mean MP transport in 2021 was 19 ± 13.6 items/m3, but it increased by 17% in 2022 (22.4 ± 14.8 items/m3). The most polluted sections were the Upper Tisza (Ukraine, Hungary) and the Lower Tisza (Serbia), where wastewater treatment is not satisfactory, whereas the Middle Tisza (Hungary) was less polluted. The tributaries increased the sediment and MP budget of the main river. Microfibers dominate (84–97%) the suspended MP transport, and thus it can be determined that they originated from wastewater. The MP transport was influenced by the availability of wastewater treatment plants, dams, tributaries, and mobilization of bottom sediments. At the low stage, no connection was found between the suspended sediment and MP particle transport.

Mathematical Model of Suspended Particles Transport in the Estuary Area, Taking into Account the Aquatic Environment Movement

A large amount of contaminants enter marine systems with river runoff, so the purpose of the study is to model the transport of suspended particles in the estuary area. To describe hydrodynamic and hydrophysical processes, the mathematical model of the suspended particles transport was used, supplemented by a three-dimensional mathematical model of hydrodynamics, used to calculate the fields of the aquatic environment movement velocity vector, and equation for calculating the variable density. The approximation of the equations for calculating the velocity field by spatial variables is based on the splitting schemes for physical processes with fluid volume of the control areas, which allows for us to consider the complex geometry of the coastline and the bottom. The suspended particles transport model is approximated using splitting schemes for two-dimensional and one-dimensional problems. Numerical experiments were carried out to simulate the aquatic environment movement in the estuary area, the multicomponent suspension deposition, as well as mixing of waters in the mouth, taking into account the different density of the aquatic environment. The used models and methods allow to significantly improve the accuracy of modeling suspended particle transport and consider the factors influencing the studied processes.

Measurement of PM2.5 and PM10 Concentrations in Nakhodka City with a Network of Automatic Monitoring Stations

The Nakhodka city – Port Vostochny urban agglomeration is Russia’s largest transport hub on the Pacific Ocean. Within Nakhodka city, there are several marine terminals involved in coal handling and shipment. An increase in coal handling leads to environmental pollution and an impact on public health. This work focuses on the concentrations of PM2.5 and PM10 in the air of Nakhodka city during the period from January to May 2021. PM concentrations were measured using a network of automatic monitoring stations deployed in 5 districts of Nakhodka city. Data on PM2.5 and PM10 concentrations were averaged by months. According to the results obtained, the highest concentrations of PM10 and PM2.5 were observed in the winter months, and then there was a gradual decrease in concentrations at all observation points. Elevated concentrations of particulate matter were observed to the north of the Nakhodka port, which is due to the proximity to the port infrastructure and the railroad, as well as in the central part of the city. Given the specific conditions of occurrence and transport of suspended particles in the atmosphere of Nakhodka city, they can be hazardous to public health.

Simulation of microplastic particles propagation in the coastal zone of the reservoir due to wave motion

The transport of suspended microplastic particles in an aqueous medium is closely related to hydrodynamic circulation. The transfer of microplastics to and from the surf zone is largely determined by the properties of the particles, which may differ significantly in terms of chemical and physical characteristics, size, shape, degradation stage and color. Microplastic particle capture and transfer models are largely determined by phenomena such as sea storms and prevailing currents. There are several mechanisms of horizontal and vertical movement of suspended microplastic particles associated with their concentration. Depending on the prevailing wave climate and the coastal currents caused by the destruction of waves and caused by waves, precipitation is captured, transported and redistributed along and across the coastline, which often leads to erosion or seasonal bathymetric changes. In the article, a model describing the change in the concentration of suspended microplastic particles is considered, discretization is carried out, and the results of numerical experiments in two-dimensional and three-dimensional cases are obtained. The deposition and erosion of microplastics with an average grain size of 0.3 mm were compared. Data demonstrating the amount of erosion and deposition in two-dimensional and three-dimensional cases were obtained. The results of both the analytical model and numerical simulation demonstrate that waves can affect the distribution of floating particles near a free surface. The results of numerical simulation are largely consistent with the theory.

Effect of fracture roughness on transport of suspended particles in fracture during drilling

Fractures with different roughness are important permeable channels in oil and gas reservoirs. However, the drilling fluid is prone to leakage through fractures, resulting in formation damage. Study on the migration behavior of suspended particles with drilling fluid loss is the basis for finding the damage mechanism of solid invasion and drilling fluid loss control measures. From a comprehensive review of the previous studies, the transport behavior of suspended particles considering particle-fluid-fracture interaction hasn't been fully understood and quantified. In this study, we examined flow behavior of the particle-fluid mixture by the unresolved CFD-DEM approach. The effects of particle concentration, particle size, fracture width, drilling fluid loss rate, drilling fluid viscosity and cohesive force on particle transport in different rough fractures were studied. The research suggests that: (1) Increase of particle concentration will not only result in significant increase in fluid-particle velocity, but will also increase the wall mechanical retardation. (2) Particle aggregation near the fracture walls is more serious than in the fracture center. The shape of the agglomeration particle clusters is mainly elongated, with the long axis direction consistent with the flow direction. (3) Rough fracture walls will not only lead to more energy loss due to frequent particle-particle and particle-fracture contact, but also cause more particles to migrate in the fracture center.

Coupling between physical processes and biogeochemistry of suspended particles over the inner shelf mud in the East China Sea

This study examines how geochemical signals regarding the source and transformation in suspended particles are transported in the marine portion of the sediment dispersal system. In the source-to-sink sedimentary continuum of a world major river, the Changjiang (Yangtze) River, is used to demonstrate the close coupling between the marine physical processes and the geochemical signals carried by suspended particles. A sediment trap mooring configured with a non-sequential sediment trap, a downward-looking ADCP, CTD, LISST-100× were deployed for 29 days in the winter of 2014 off the coast of Zhejiang Province, China in water depth of 22.5 m. The mooring rendered two types of data. Physical processes included temporal changes of water depth, currents at 11 depths, temperature at two depths, and salinity at one depth. There was 15-cm accumulation of captured particles in the trap, which rendered the total mass flux of 233.3 g/cm2/day. The trap material was analyzed for grain-size composition, total 210Pb, minerals including mica/illite, kaolinite, chlorite, k-feldspar, plagioclase, quartz, and dolomite. Organic material (TOC, TN) and carbon isotope δ13C were also measured. The range of terrestrial fraction (Ft) of the trap material was between 45–60%. EOF analysis was used to examine the covariability in both data sets. For the physical data set, 37 variables were used in the analysis. For the sediment trap material, 15 variables were used. The EOF results of the physical processes indicate the tidal flow was the most important physical forcing for the transport of suspended particles and water masses that carried marine- and terrestrial-sourced particles. Wave and current combined resuspension entrained reworked sediment off the seabed, which was then transported landward or seaward. The most important covariability of the particle properties in the sediment trap was caused by hydrodynamic sorting that separated the clay from silt and sand sizes. Geochemical signals of the particles were carried by clay and the particle mass (dry weight) was associated with silt and sand. The temporal characteristics of the sorting show the spring-neap tidal cycle. The next major distinction was the contrast between terrestrial- and marine-sourced materials. The EOF analysis further distinguish contributions from the distal Changjiang River and proximal small rivers at the tertiary level of the covariability. The coverabilities in both data sets show close correspondence. Our findings give firm evidence to show marine processes dominated the transport of land-derived fluvial sediment and the incorporation of marine-sourced particles into the dispersal system. There is complexity in both physical processes and geochemical signals of suspended particles. However, our study points out the close coupling between the two.

Assessment of the spread of pollution in the riverbed of the Neva River as a result of an emergency at a toxic waste landfill

The catchment area of the Neva River, which includes the largest European lakes Ladoga, Onega, Ilmen and Saimaa, located in Finland, has an area of 183,300 km2. The quality of water in the Neva River is determined by the characteristics of the water masses of Lake Ladoga, as well as by point and non-point sources of pollution on the tributaries of the Neva. One of the potential sources of pollution is the Krasny Bor landfill for storing highly toxic waste of hazard classes I – V. In the event of an emergency at the landfill, toxic wastewater can enter the Izhora River, and then into the Neva River, 7 km above the water intakes of St. Petersburg. Using the methods of mathematical modeling, the calculation of the spread of toxic substances in the hydrographic network of the catchment area, and then in the channel of the Neva River was carried out under various scenarios of the development of an emergency at the landfill. A full-scale experiment was carried out to confirm the adequacy of the model of impurity spreading in the channel of the Neva. An assessment of the features of the transport of suspended particles and dissolved impurities in the direction of the water intakes of St. Petersburg is given.

Suspended particle transport process modeling based on 2D and 3D models

In this paper, suspended particles transport mathematical model is proposed and investigated. The considered model includes the following factors: the aquatic environment movement; variable density depending on the suspension concentration; multicomponent suspension; change in the bottom geometry as suspension sedimentation result. The 3D diffusion-convection equation approximation based on splitting schemes into 2D and one-dimensional problems. In the paper, convective and diffusive transfer operators’ discrete analogs in the case of partial fullness of the cells are used. Based on the fullness function, the calculated area geometry is described. The difference scheme, which is linear combination of the Upwind and Standard Leapfrog difference schemes with weight coefficients obtained from the condition of minimizing the approximation error, is used. This scheme is designed to solve the impurity transfer problem at large grid Peclet numbers. Based on the results of numerical experiments, conclusions are drawn about the advantages of the 3D model of suspended particle transport over the 2D model. The results of numerical experiments on modeling the multicomponent suspension deposition are presented.

A novel CFD-DEM upscaling method for prediction of scour under live-bed conditions

Despite intensive research efforts, the accurate modelling and prediction of bridge pier scour is an outstanding challenge due to the complexities arising from the detailed interactions between granular and fluid mechanics in the riverbed. Pier scour predictions based on empirical formulas are used in conventional bridge design codes which fail to realistically account for these interactions, and thus fail to facilitate pier design optimization. A critical step towards optimal pier design is an improved physical understanding of detailed mechanisms of the scour process and the development of appropriate modelling techniques to resolve these mechanisms in engineering applications. In this study, a combination of computational fluid dynamics (CFD) and discrete element modelling (DEM) is used to improve physical understanding of the scour process, including detailed interactions between river hydrodynamics, transport of suspended particles, and granular mechanics of the riverbed. As CFD-DEM models of turbulent hydrodynamics coupled with densely packed granular assemblies are computationally expensive, it is currently not feasible to accurately model scour in macroscopic engineering applications. To address this problem, we propose a novel upscaling methodology based on highly-resolved microscale simulations that significantly reduces the computational overhead, facilitating macroscopic prediction of scour under live-bed conditions. Predictions of scour initiation, rate and extent from these microscale simulations have been validated against previously published experimental data. Results indicate that the microscale model is reasonably capable of predicting the scour initiation as well as the equilibrium scour depth. This upscaling model provides a viable methodology for the macroscopic prediction of scour in engineering applications with modest computational resources.

Direct Laser Writing for Deterministic Lateral Displacement of Submicron Particles

Emerging additive manufacturing (or “three-dimensional (3D) printing”) strategies offer the potential to vastly extend the capabilities of established microfluidic technologies. For example, the operational performance of “deterministic lateral displacement (DLD)” - a technique in which micro/nanoposts arrayed inside of a microfluidic channel enable passive transport of target suspended particles away from their initial flow streams - is based on geometric design variables, such as the gap spacing between the arrayed posts (G). For applications that involve DLD processing of submicron-scale particles (e.g., extracellular vesicles), however, achieving the requisite geometric control via conventional microfabrication protocols represents a technically challenging manufacturing hurdle. To bypass such barriers, here we explore the use of two-photon “direct laser writing (DLW)” for additively manufacturing DLD arrays capable of submicron particle handling. Studies of DLW fabrication conditions revealed that increasing the laser power from 22.5 mW to 27.5 mW significantly decreased G from 1.51±0.04 μm to 1.02±0.05 μm, respectively. Experimental microfluidic testing of 860 nm-in-diameter fluorescent particles within the DLW-printed DLD system revealed effective hydrodynamic railing of particles along the angled arrayed microposts, with a lateral displacement of 15.3±8.6 μm over a channel length of 500 μm. These results represent, to our knowledge, the first report of a 3D printed DLD system capable of processing submicron particles, thereby offering a promising foundation for DLW-enabled DLD-based biomedical applications.

Transport of inertial particles in high-Reynolds-number turbulent boundary layers

Abstract