Clogging Behavior Research Articles

Effect of Direct Current Electric Field on the Clogging Behavior of Submerged Entry Nozzle During Casting of UltraLow‐Carbon Steel

Effect of Direct Current Electric Field on the Clogging Behavior of Submerged Entry Nozzle During Casting of UltraLow‐Carbon Steel

Real-time two-dimensional visualization reveals the transport mechanisms of biochar colloids in the presence of DOM in porous media

Biochar colloids (BCs) have attracted much attention globally, and their fate and transport in the subsurface are significantly influenced by soil-dissolved organic matter (DOM) in soil. This study utilized a real-time and non-invasive visualization system to reveal the transport and retention behavior of BCs in the presence of DOM in two-dimensional porous media. Results indicated that the presence of DOM enhanced the transport of BCs, due to its increased negative charge density and increased repulsion between BCs. The change in the particle size of the porous medium was also shown to affect the BCs transport in the porous media. Additionally, the negative charge of BCs shielded by high IS, the mobility of BCs decreased by 30.37 % from 1 mM to 50 mM. When the pH was increased from 5 to 9, the oxygen-containing functional groups of BCs and DOM were dissociated, and the mobility of BCs increased by 32.41 %. Through a simplified Double-Monod model, we fitted the breakthrough curves for BCs transport in porous media (R2 > 0.94). Moreover, the mechanism of different conditions on colloid clogging behavior was further elucidated through the DLVO theory. These findings extend the understanding of the environmental behavior of BCs in the presence of DOM derived from soil, enabling us to assess better and predict their environmental risks.

Pore-scale investigation of injectivity impairment caused by oil droplets during produced water reinjection using volume of fluid method

Produced water from subsurface may often contain oil droplets, even when not directly extracted from oil wells. Oil droplets can migrate into water-bearing stratigraphic layers, leading to the generation of oily water. This study evaluates the dynamic clogging behavior of oil droplets concerning various injection fluid properties, including injection velocity, interfacial tension, oil droplet size, concentration, viscosity, and medium wettability. The primary objective is to validate common clogging mechanisms associated with oil droplets and quantitatively assess the impact of these parameters on injectivity impairment within porous media. To achieve this, a volume of fluid approach is employed, integrating fluid interfacial properties to account for coalescence and surface adherence. The results are then compared to similar findings in existing literature. Our study reveals that increasing the capillary number enhances injectivity, up to a critical point where the flow regime attains optimal stability, contingent upon relative permeability and phase mobility. Investigation into system wettability demonstrates that while contact angle significantly affects the injectivity index, the impact on injectivity diminishes when altering it beyond 90°. Aligning droplet viscosity with that of the displacing fluid proves to be an effective solution for minimizing injectivity impairment, nearly eliminating damage. This research provides valuable insights into commonly studied emulsion parameters, like Jamin Ratio and oil concentration, and underlines the importance of investigating less-explored factors, such as wettability and oil viscosity, particularly in scenarios involving unstabilized droplets and coalescence dynamics.

Study on the pore blocking characteristics and cleaning methods of permeable asphalt mixtures based on accelerated clogging simulation experiments

Clogging in permeable asphalt pavements compromises their functional properties. Understanding clogging characteristics and developing appropriate maintenance methods is crucial. This study integrates indoor accelerated clogging simulations with Grey Relational Analysis to investigate the factors influencing clogging behavior. Computer tomography scanning and seepage model simulations are utilized to examine the distribution of clogging materials, seepage properties, and changes in pore parameters in permeable asphalt mixtures before and after clogging. Additionally, variable frequency vibration tests are conducted to evaluate the impact of vibration frequency on clog removal efficiency. Findings show that the cementation hardening effect of clay progressively seals pores, with sand particles of 0.15 mm diameter exerting the most significant influence on clogging. Wet-dry cycles lead to an accumulation of clay cementation, resulting in a 26.1 % and 72.4 % decrease in pore channel length and volume, respectively, at depths of 0–4.2 cm. The area within this depth range is most prone to clogging, increasing pore tortuosity. Seepage behavior is primarily determined by several main interconnected pores. Vibration test outcomes indicate that frequencies between 100 and 400 Hz are optimal for disrupting cementation blockages.

Flow and clogging behavior of a mixture of particles in a silo

We investigated the clogging behavior observed during the flow of aspherical particles from a silo in the presence of spherical particles of different sizes and proportions using flow visualization experiments and discrete element method simulations. The size of the avalanche, essentially the tendency of clogging, exhibits non-monotonic dependence on the spherical particle volume fraction. For small enough content of spherical particles, the clogging tendency intensifies, whereas it reduces rapidly for high enough spherical particle fractions, with a minimum in between. The non-monotonic behavior is observed to persist over for different spherical particle sizes. The overall behavior is shown to arise due to competing effects between the localized total particle fraction influencing avalanche strength and mean size of the particles exiting the silo, influencing the probability of arch formation.

Understanding Penetration Attenuation of Permeable Concrete: A Hybrid Artificial Intelligence Technique Based on Particle Swarm Optimization

Permeable concrete is a type of porous concrete with the special function of water permeability, but the permeability of permeable concrete will decrease gradually due to the clogging behavior arising from the surrounding environment. To reliably characterize the clogging behavior of permeable concrete, particle swarm optimization (PSO) and random forest (RF) hybrid artificial intelligence techniques were developed in this study to predict the permeability coefficient of permeable concrete and optimize the aggregate mix ratio of permeable concrete. Firstly, a reliable database was collected and established to characterize the input and output variables for the machine learning. Then, PSO and 10-fold cross-validation were used to optimize the hyperparameters of the RF model using the training and testing datasets. Finally, the accuracy of the developed model was verified by comparing the predicted value with the actual value of the permeability coefficients (R = 0.978 and RMSE = 1.3638 for the training dataset; R = 0.9734 and RMSE = 2.3246 for the testing dataset). The proposed model can provide reliable predictions of the clogging behavior that permeable concrete may face and the trend of its development.

Modelling clogging dynamics in groundwater systems using multiscale homogenized physics informed neural network (MHPINN)

Groundwater systems, or also commonly known as large-scale closed and saturated porous media systems in general, are important sources of potable water, especially in arid countries. However, maintenance of groundwater systems is operationally expensive and time-consuming, hence requiring field engineers to optimally predict the system’s breakthrough phase. To address this engineering challenge, this study developed an alternative physics informed machine learning model, termed as multiscale homogenized physics informed neural network (MHPINN), to model and predict the effluent discharge concentrations from closed and saturated porous media systems when removing different contaminants. The proposed MHPINN model mainly exploits the homogenization theory, coupled with multiscale perturbation analysis, for hydrodynamic modelling to extract important model input features pertaining to the pore-scale clogging behavior in porous media. Together with available experimental data, the extracted model features then set the input layer for training neural network model to predict the discharge concentration of emulated porous media groundwater systems. At the same time, the model training is performed with modified mean square error (MSE) cost function, based upon homogenized mathematical representations derived from a series of rigorous mathematical constructs and formulations, to better facilitate the model’s learning, especially under sparse data constraint. To verify the proposed methodology, MPINN is trained (and validated) with data obtained from five historical experimental studies, which emulated porous media systems to remove ammonium ions and fine-scaled colloids, to model and predict the discharge concentration in each study. Overall, MHPINN outperformed other conventional machine learning models (random forest, support vector machines, etc.) by obtaining higher predictive accuracy of around 4% on average from the model’s validation step across the five different experimental studies. Therefore, the predictive analysis underscored the effectiveness of MHPINN to combine both physics-based modelling and machine learning to model complex porous media systems, under sparse experimental data constraints, hence demonstrating the potential of the proposed methodology to extend to other physical systems.

Experimental Investigation of the Effects of Aperture Ratio, Chamber Pressure and Soil Conditioning on the Clogging Behavior of EPB Shields

Earth pressure balance (EPB) shield excavation in cohesive strata frequently encounters cutterhead clogging, consuming time and economic costs. Engineering practice shows that cutterhead aperture ratio, soil chamber pressure and soil conditioning have important influences on the clogging behavior of EPB shields. In order to study these factors, a series of laboratory tests were conducted using a setup that can closely simulate the shield tunnelling process. The indicators analyzed were excavation speed, torque, specific energy and soil distribution on the cutterhead. The results indicate that cutterhead aperture and cutter arrangement are important factors in clogging potential. Clogging creates a significant reduction in excavation speed. Torque is not a sensitive parameter reflecting clogging because of the effect of the consolidated soil on the cutters. The presence of soil chamber pressure makes it difficult to remove the clogging through the shearing action of the excavation surface. The injection of a sufficient amount of foam can reduce the risk of shield clogging, but it may lead to an increase of soil adhesion on the cutterhead. The amount of soil that adheres to the cutterhead cannot be used as a classification criterion for clogging potential. Based on experimental phenomena and established studies, a mechanical model called ‘beam-bridge’ was proposed to study the behavior of the soil through the cutterhead opening and damage form of clogging. The results will help to the excavation control of EPB shields.

Assessing clogging potential and optimizing driving parameter of slurry shield tunneling in clay stratum assisted with CFD-DEM modeling

This paper proposed a two-way coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach to analyze the evolution of clogging in slurry shield tunneling quantitatively. The interactions between clay particles and slurry were considered by exchanging three interaction forces, including buoyancy force, pressure gradient force, and drag force. The CFD-DEM coupling approach was first benchmarked by comparing cutterhead torque and total thrust with field monitored data of a practical slurry shield tunnel project. The evolution process of the particle phase and the fluid phase over time was presented. The results indicated that fewer than 70% of the particles can be washed away in time by the circulating slurry. About 9% of the particles adhered to the submerged wall, resulting in increased cutterhead torque and thrust. Through parametric analysis, the influence of the shield driving parameters on the clay clogging behavior is further explored. The time history of cutterhead torque or thrust can be used as a criterion for judging whether clogging has occurred. Additionally, a new assessment method of clogging risk and an optimization strategy of driving parameters were proposed, which were intended to provide some guidance for similar projects.

Development of Sewage Pumps with Numerical and Experimental Support

Especially in the field of sewage pumps, the design of radial impellers focuses not only on maximum efficiency but also on functionality in terms of susceptibility to clogging by fibrous media. In general, the efficiency of sewage impellers is significantly lower than that of clear water impellers. These sewage impellers are designed with a low number of blades to ensure that fibrous media can be pumped. This paper describes the methodology of an optimisation for a sewage impeller. The optimisation is carried out on a semi-open two-channel impeller as an example. Therefore, a new impeller is designed for a given volute casing. Based on a basic design for given boundary conditions, the impeller is verified by means of numerical simulation. The manufactured impeller is then tested on the test rig to verify the simulation. With regard to the optical investigations, the clogging behaviour of the impeller is specifically improved over three different modifications in order to finally present an impeller with good efficiency and a low clogging tendency.

Effect of Seepage Velocity on Pore Clogging Growth Behavior and Its Effect on Permeability Reduction During Fines Migration in Porous Media

AbstractFines migration driven by fluid flows often causes pore clogging in porous media and thus reduces the permeability of the porous media. The clogging can pose serious problems in various practices, such as formation damage in hydrocarbon reservoirs, degradation of fluid withdrawal or injection efficiency, particle‐induced fouling in filtration membranes, or even a risk of sediment failure with geostructures. However, the effect of seepage flow velocity on the spatial growth pattern of fines‐induced pore clogging remains poorly identified. This study explores the pore clogging growth behaviors caused by flow‐driven fines migration and accumulation in porous media and the associated permeability reductions through a series of column experiments and concurrent X‐ray computed tomography imaging. Particularly, the X‐ray image analysis captures the spatial distributions of fines, and thus the homogeneous or heterogeneous (localized) clogging growth pattern under various seepage velocities. Our results reveal that an increase in the seepage flow velocity increases the likelihood of localized clogging growth, attributable to the direct interception of fines by the sand grains. The localized clogging growth causes a faster reduction in permeability than the homogeneous clogging growth. The presented study provides well‐controlled experiment data on fines distribution and associated permeability change, which gives insights into fines‐induced clogging behavior in porous media.

Characterization of a Modular Microfluidic Section for Seeded Nucleation in Multiphase Flow

We present a proof-of-concept modular nucleation section for seeded multiphase flow crystallization of an active pharmaceutical ingredient. The setup can be used in four different modes of operation (with or without off-line prepared seeds and with or without a stream of microbubbles). The setup is characterized to provide insights into the design and operation of crystallization processes. First, the performance of the off-line continuous seeding platform is established via the seed delivery efficiency for constant and oscillatory flows. Second, the yields of seeded and unseeded crystallization are evaluated in the presence and absence of microbubbles. A statistically significant increase in the net crystal mass and net yield was measured when comparing unseeded and seeded crystallization, which can be attributed to the increased nucleation rates as a result of secondary nucleation. Third, the clogging behavior of the presented continuous microcrystallizer is discussed. Finally, also the crystal size distribution is analyzed: the mean crystal size decreases for both single- and two-phase flow when seeds are introduced. The presence of microbubbles resulted in a higher net yield and slightly smaller crystals compared to that of the single-phase flow. This work highlights the importance of a holistic characterization approach for continuous microfluidic crystallizers.

Three-Dimensional Visualization Reveals Pore-Scale Mechanisms of Colloid Transport and Retention in Two-Phase Flow.

Colloids are ubiquitous in the natural environment, playing an important role in facilitating the transport of absorbed contaminants. However, due to the complexities arising from two-phase flow and difficulties in three-dimensional observations, the detailed mechanisms of colloid transport and retention under two-phase flow are still not well understood. In this work, we visualize the colloid transport and retention during immiscible two-phase flow based on confocal microscopy. We find that the colloid transport and retention behaviors depend strongly on the flow rate and pore/grain size. At low levels of saturation (high flow rate) with the wetting liquid mainly present as pendular rings, the colloids can aggregate at the liquid filaments in small-grain packings and are uniformly distributed in large-grain packings. Through theoretical analysis of the pendular ring geometry, we elucidate the mechanism responsible for the strong dependence of colloid clogging behavior on solid grain size. Our results further demonstrate that even at dilute concentrations, colloids can alter the flow paths and the wetting fluid topology, suggesting a strong two-way coupling dynamics between immiscible two-phase flow and colloid transport and calling for improved predictive models to incorporate the overlooked clogging behavior.

Long-term permeability tests on clogging and permeability of nonwoven geotextile filtering silty clay

Geotextile filters have gained extensive applications in geotechnical and geoenvironmental drainage systems. Despite of the abundant research about geotextiles filtering coarse-grained soils, there is little experimental study on the performance of geotextiles filtering fine-grained soils. Since clogging and blinding of geotextiles are more likely to occur in clayey soils, a complex filtration performance of the filters is expected, posing great challenges to the long-term durability of the filtration system. In this research, long-term permeability tests were conducted on silty clay filtrated by three types of nonwoven needle-punched geotextiles. Comprehensive results regarding the permeability evolution, soil retention and clogging behavior were obtained. Interior clogging behavior of the geotextile was checked after the tests by means of scanning electron microscopy. Significant reduction around two orders of magnitude from 10−8 m/s to 10−10 m/s was observed in the permeability coefficient of the silty clay-geotextile system after 90 days of seepage flow. The influence of filtration opening size of the geotextile was obviously noticed in the initial permeation process, while the thickness played an increasingly important role at the later stage. Geotextile with the larger thickness and smaller filtration opening size had more soil retention and poorer filtration performance. In addition, a theoretical equation relating permeability coefficient and filtration opening size of nonwoven geotextile under clogged condition was proposed.

Characteristics of SEN clogging and adhesive behavior of oxide inclusion during continuous casting of Ti-stabilized ultra-pure ferritic stainless steels

Characteristics of SEN clogging and adhesive behavior of oxide inclusion during continuous casting of Ti-stabilized ultra-pure ferritic stainless steels

Influence of the injection of densified polymer suspension on the efficiency of DNAPL displacement in contaminated saturated soils

Nowadays the remediation of DNAPL contaminated zones near groundwater has gained great prominence in environmental fields due to the high importance of water resources. In this work, we suggest injecting a densified polymer suspension by adding barite particles to displace DNAPL. To evaluate the efficiency of the densification of polymer suspensions on the displacement of DNAPL, various densities of barite-polymer suspension; lower, equal, and higher than the density of DNAPL were prepared and their rheological behavior was analyzed. Then flow experiments were performed using a decimetric-scale 2D tank. The displacement procedure was monitored with an imaging technique and the production and injection process data were recorded by mass balance interpretation. It was shown that the densification of the polymer suspension could improve the displacement efficiency of DNAPL up to four times. The clogging behavior of barite-polymer suspension was assessed in a 1D column. Generalized Darcy’s law and the continuity equation were used to numerically simulate the experimental two-phase flow. To take into account the clogging behavior of the suspension, the transport equation of diluted species was implemented into the model. The simulation results show that the model can properly predicts the experimental consequences.

Numerical study on clogging mechanism of slurry infiltration in porous media based on coupled CFD-DEM method

The clogging behavior of particles is a ubiquitous phenomenon. In slurry support, the clogging behavior of slurry particles is expected to occur rapidly, but the microscopic mechanism is not well understood at present. The common penetration column test can only analyze some macroscopic parameters; it cannot track the movement of particles. In order to investigate the clogging mechanism and migration of slurry particles, a coupled CFD-DEM model of the penetration column test is employed in this paper. Based on a previous experimental study (Lin et al., 2021), the numerical model was appropriately simplified. The simulation results indicate that the apertures of homogeneous porous media have a minimum value; particles bigger than this value will be trapped and particles smaller than this value will escape. Furthermore, there is a maximum value; particles smaller than this value have the chance to enter the ground. Smaller particles always have longer trails than bigger ones before being captured. Pores of different sizes are distributed according to a certain rule in porous media, which leads to dispersed local clogs at the beginning of the infiltration. When large pores are blocked, local clogs will converge to the overall clog on a plane (i.e., filter cake). The simulation in this paper reveals the evolution process from local clog to overall clog, which can be summarized as a process from point (local clog) to surface (overall clog). This indicates that future models can focus on a pore rather than the entire ground, which could greatly reduce computational effort and leave more space to simulate more and smaller particles. This study provides a new insight for slurry infiltration and offers a reference for other similar investigations.

Drainability and Clogging Behavior of Open-Graded Asphalt Friction Courses with Basic Oxygen Furnace Steel Slag Aggregates

Drainability of an open-graded asphalt friction course (OGAFC) is a primary functional requirement, which mainly depends on the presence of a network of interconnected air voids. These mixtures, however, are prone to clogging, which severely limits their drainability. Clogging predominantly occurs as a result of the deposition of external (sand, debris, and dust) and internal (stripped-off bitumen) materials into the pores of OGAFC, which is referred to as particle-related clogging. Another type of clogging is deformation-related clogging and it is observed mainly because of rutting along the wheel path. In this study, the drainability and clogging behavior of OGAFC mixes with basic oxygen furnace (BOF) steel slag as replacement of natural aggregates was studied. BOF steel slag was used as 0% (control mix), 25%, 50%, 75%, and 100% substitution for coarse natural aggregates in the preparation of OGAFC mixes with two types of modified binders. Three different clogging mechanisms: particle-related clogging (caused by intrusion of foreign material such as sand); stripping-related clogging (caused by the deposition of stripped-off bitumen-fines mortar), and deformation-related clogging (reduced drainability caused by permanent deformation) were considered in this study. Comparisons were made to investigate the effect of BOF steel slag on the clogging potential of OGAFC mixes. OGAFC specimens were evaluated for their drainage potential using a flexible-wall falling-head permeameter both before and after being subjected to various clogging environments. BOF-steel-slag-incorporated OGAFC mixes exhibited lower clogging potential and reported better performance in resisting clogging resulting from stripping and permanent deformation.

Physical, chemical and biological emitter clogging behaviors in drip irrigation systems using high-sediment loaded water

High-sediment water in drip irrigation (HSWDI) technology offers the opportunity to alleviate water shortages in agricultural irrigation. Emitter clogging, caused by active suspended particles, salt ions, and microorganisms present in water with high sediment load, poses considerable technical challenges to HSWDI. To date, emitter blockage of HSWDI is attributed to physical clogging, little is known about the physical, chemical, and biological clogging behaviors and their interactions for HSWDI. Here, X-ray diffraction and 16S rRNA gene sequencing were applied to determine the physicochemical minerals and microbial community structure of the foulants for HSWDI, using three types of flat emitters and two fertilization modes (no-fertigation and fertigation with ammonium polyphosphate, APP). Results indicated that HSWDI emitter clogging was not only caused by physical clogging (induced by particulates) but also caused by chemical clogging (i.e., precipitates) and biological clogging (i.e., biofilms). The main particulates in HSWDI were found to be quartz (accounting for 41.8–56.3% of total clogging foulants) and feldspar (13.6–21.1%), while the precipitates that contained calcite, dolomite and aragonite contributed 14.6–26.7%. The dominant flora in foulants were Proteobacteria (relative abundance ranged: 41.7–53.9%) and Bacteroidetes (13.6–17.3%). Moreover, the coupling effect of three types of fouling was the main reason affecting clogging (accounting for 36.3%), while the effect of two or single fouling was less (accounting for 14.4–25.3% and 0.7–2.6%). In addition, APP application caused the increase in microbial diversity and the proliferation of microorganisms, resulting in the interactions between biofilm and other two foulants (i.e., precipitates and particulates) were exacerbated, thus aggravating emitter clogging. This study opens a frontier for the investigation of physical, chemical, and biological clogging behavior, in-depth clogging mechanisms, and anti-clogging measures for HSWDI, which will facilitate the utilization of high-sediment water in agricultural irrigation.

Microstructural Characterization of the Corrosion Product Deposit in the Flow-Accelerated Region in High-Temperature Water

The clogging behavior of the micro-orifice under a flow accelerated condition was investigated after 500 h of immersion in high-temperature water. The results indicated the residual area of the micro-orifice was reduced to one-third of its original size after 500 h of immersion due to the deposition of corrosion products. In this process, the clogging behavior of micro-orifice can be divided into three stages: the stable deposition stage, the quick recovery stage, and the dynamic equilibrium stage. The corrosion products were porous and consisted of many deposited particles. The process of particle deposition and removal was carried out simultaneously.