Bedforms Research Articles

Session 25. Oral Presentation for: Deep bed filtration and formation damage by particles with distributed properties

Session 25. Oral Presentation for: Deep bed filtration and formation damage by particles with distributed properties

STAR-CCM+ simulation of debris bed formation in the unheated DEFCON-S experiment

In a severe accident of light-water reactor, molten corium can be formed and discharged into the reactor cavity. If the resulting debris bed is not adequately cooled, it could threaten the containment integrity by causing a molten core-concrete interaction. This study analyzes a non-heating debris bed formation experiment of DEFCON-S using the STAR-CCM+ code. Relevant CFD models are established to reflect the interaction between particles and fluids to describe the particle behavior and flow of fluids. The shape and size of debris bed are predicted through the CFD calculation. The rolling resistance becomes an important parameter in this simulation. The prediction with the default values of STAR-CCM+ forms a spread shape of particle bed compared to the experimental result. The shape of debris bed obtained with modified rolling resistance coefficients gives consistency with the DEFCON-S experiment, having a deviation in diameter of 4.6 % and a deviation in height of 3.8 %.

Flow resistance of emergent rigid vegetation in steady flow

Abstract Enhanced understanding of flow resistance in open channels with emergent vegetation is essential for flood management and river ecosystem restoration. The presence of vegetation can significantly alter bed resistance, leading to a challenge in accurately predicting flow discharge, water levels, sediment transport, and bed deformation. Previous studies on vegetated flows have focused on vegetation resistance, on which the impact of vegetation has been ignored or poorly estimated. This study proposes a new analytical model, built upon the momentum conservation law, to predict flow resistance to vegetated zones in a plain bed without bed forms, explicitly quantifying bed resistance and vegetation resistance in a corollary manner. The proposed model is benchmarked against five typical sets of laboratory experiments. It is demonstrated that the present model using a modified logarithmic velocity distribution performs best, whereas that assuming a uniform velocity profile considerably overestimates the vegetation resistance and neglects the effect of vegetation on bed resistance. The ratio of bed resistance to the total resistance is shown to range between 5% and 40%, and it decreases with increasing vegetation density and decreases with water depth. Therefore, bed resistance cannot be ignored when modelling shallow water flow with sparsely distributed vegetation. It is also revealed that vegetation arrangements significantly affect flow resistance, and therefore a model incorporating the effect of vegetation arrangement performs better. Overall, the present model facilitates a viable and promising tool for quantifying flow resistance in emergent vegetated channels.

Exploring the Mineral Composition, Structure, and Function of a Freshwater Bivalve Adhesive

AbstractEtheria elliptica is a freshwater oyster that produces an adhesive that hardens underwater, allowing them to attach to other oysters, rocks, wood, and other natural substrates, producing complex oyster bed communities. Despite the importance of the adhesive in oyster bed formation, little is known about its chemical composition, structure, or mechanical properties. Through a combination of scanning electron microscopy (SEM), x‐ray photoemission electron microscopy (X‐PEEM), infrared (IR) spectroscopy, microhardness testing, and nanoindentation, it is found that the oyster adhesive consists entirely of aragonite nanoparticles that clump together into crystallites of varied shape, size, and orientation. The crystallite clumping density varies from the exterior of the adhesive to the interior, with the adhesive closest to the prismatic layer generally being denser. With this variation in density comes a variation in material properties with the exterior adhesive layer being softer and more flexible and the interior adhesive layer being harder and less elastic, or more similar to the prismatic and nacre shell structures produced by the E. elliptica. The resultant material exhibits varied materials properties, despite similar mineral composition.

Hydraulic investigation of flow and bed load transport in diverging compound channels with rigid and flexible vegetation

Floodplains are really important for the environment as they provide various functions for waterways, including ecological, hydrological, and geomorphic ones. During overbank flows, there are complex hydrodynamic conditions that occur as water interacts with the rough floodplain vegetation and drag forces due to the vegetation that changes the flow pattern. However, we still don't fully understand how floodplain vegetation influences channel-altering hydrodynamic forces and sediment transport. To address this, we conducted flume experiments and measured flow pattern and sediment transport under varied floodplain geometry and rigid and flexible conditions. For this purpose, a physical model was constructed in the laboratory, in which plastic rods with a diameter of 10 mm will be used as trees, and artificial grass will be grass vegetation. Thus, 36 experiments were conducted in which the sedimentation and hydraulic parameters of the flow were calculated by measuring the flow velocity, water surface, and sediment transport rate. The results show that in the floodplain with dense (rigid and flexible) vegetation, the friction coefficient (f) is even 1.5 times higher than in the floodplain without vegetation. The parameters such as flow velocity, bed shear stress and Darcy Weissbach friction coefficient increase in the vertical plane between the main channel and floodplains due to the difference in roughness between the main channel and floodplains. In addition, in the main channel, the flow resistance is almost constant and does not depend on the vegetation density. The Darcy-Weissbach friction coefficient is greatly increased in the presence of grass and tree vegetation on the floodplain, and the larger contribution of f is due to the grass vegetation. The results also showed the sediment transport rate has a direct relationship with the angle of divergence and density of vegetation and an inverse relationship with the relative depth of the flow. Therefore, as the sediment transport rate decreases in the diverging compound channel, the wavelength and height of the dunes increase. At smaller divergence angles, the dunes tend to the top of the zero line (the level of the sediments before the formation of the bed form). In the presence of vegetation, due to the increase in the roughness ratio of the floodplain to the main channel, the contribution of the main channel to the flow rate increases. As a result, the sediment transport rate increases.

Prediction of burden distribution and electrical resistance in submerged arc furnaces using discrete element method modelling

A computational model of a submerged arc furnace (SAF) used in the production of ferrochrome is presented. The model's intended use is to investigate the extent to which intrinsic and extrinsic properties of the raw materials affect burden distribution and electrical resistance within the furnace. The model is built on the discrete element method and calculates the mechanical interactions of particle distributions resulting from the flow motion of typical raw materials used in the smelting of chromium ore. This model excludes the effects of thermodynamics, furnace chemistry, and heat transfer. It illustrates how the consumption of materials (chromite pellets, flux, and reductant) is affected by changes in electrode length, reductant fractions, and reductant sizing and density during the formation of a reductant bed. The resistance calculation algorithm developed by Mintek was applied to construct networks developed from particle contacts, which can quantitatively generate estimates of the electrode-to-electrode and electrode-to-bath electrical conduction conditions.

DETERMINATION OF PHYSICAL AND CHEMICAL PARAMETERS OF WATER BEFORE AND AFTER ION EXCHANGE TREATMENT

In accordance with consumer requirements, the water must be adequately purified, and the corresponding parameters within the defined values. Various methods are used for this purpose, of which the ion exchange method can be highlighted as the simplest, most efficient and economically profitable. Ion exchange is a reversible process of ion exchange between a solid phase and an electrolyte solution. The ion exchanger is a macromolecular insoluble material that has chemically bound electrified groups and mobile, oppositely charged ions that compensate for this electrification. Ion exchangers are usually used in the form of compact or granular beds that fill the column through which the solution with the ions to be exchanged flows.They usually contain phenolic, carboxylic, sulfonic amino and other groups, which is why the treatment also results in decarbonization, softening, demineralization and denitrification of water. As the assessment of water quality is based on the most significant physico-chemical parameters, the aim of the work is the analysis of drinking water before and after treatment with an ion exchanger.For this purpose, organoleptic parameters such as smell, taste and color were first analyzed. After that, physico-chemical parameters were analyzed: pH values, electrical conductivity, m-alkalinity, p-alkalinity, water hardness, organic matter content, chloride content, iron and manganese content. An ion exchanger based on resin was used, which after use was regenerated by washing with NaClsolution.The analysis of the water sample, before and after the ion exchange treatment, showed that the treatment process was effective and that the decarbonization and softening of the water was carried out, whereby the water was categorized as soft water (water <9⁰dH).The analyzed water is tasteless, odorless and colorless before and after treatment. The results of the analysis showed that all the values of the analyzedphysico-chemical parametersare in accordance with the Rulebook on the Healthiness of Drinking Water(Official Gazetteof Federation of Bosnia and Herzegovina No.40/10) arebelow the maximum allowed values. KEYWORDS:water, ion exchange, physical-chemical parameters; water treatment

Some features of intrauterine development of capillaries in the head and neck area

BACKROUND: The development of capillaries in human embryogenesis is a multi-stage process influenced by genetic factors and signaling pathways, which is of interest in studying the mechanisms of vascular bed formation in the prenatal period of human development.
 AIM: To study the development of capillaries in the embryonic and early fetal periods and determine the morphological prere­quisites leading to the formation of developmental defects.
 MATERIAL AND METHODS: The biomaterial of 50 embryos and fetuses from 4 to 12 weeks was studied. A histological and electron microscopic examination of the specimens was performed in the axial plane at the level of both jaws and neck. The volume fraction of capillaries and muscle fibers in the structure of the sternocleidomastoid muscle was determined. Data on the volume fraction of each component were presented as median and interquartile range. Quantitative analysis was performed using the Kruskal–Wallis and Mann–Whitney methods with Bonferroni correction.
 RESULTS: At the 4th week, a capillary network began to develop from the mesenchyme, which took on a complete form by the 8th–10th week. The proportion of capillaries increased from the 6th to the 10th week, and by the 12th week it decreased. A statistically significant pattern of changes in the ratio of the proportion of capillaries in muscles with the volume fraction of muscle fibers itself was revealed. As the mass of the muscle fibers themselves increased, the proportion of capillaries in it decreased significantly from 1.92 (1.77; 2)% at 4–6 weeks of embryogenesis to 0.25 (0.23; 0.26)% at 10–12 weeks.
 CONCLUSION: The critical period for the development of capillaries is the intrauterine period from the 4th to the 12th week of development, when in the structure of muscles as an organ, the vascular component first prevails over the muscular component itself, and then sharply decreases.

On the existence of flux as a function of the surface elevation for long wave solution of shallow water equations

The shallow water equations in mechanics of fluids, govern the motion of a shallow layer of water over a fixed impervious bed. In this paper, the bed form is assumed to be rough and horizontal, and the motion of water is assumed to be of the long wave type (Lamb [1], pp. 254-256) such that the free surface has a gradually varying propagating profile. Gravitation permits such motion but is resisted by the turbulence generated by the bed friction. A model of the governing equations based on the Reynolds averaged Navier-Stokes equations has recently been given by Bose [2], which is highly nonlinear. A heuristic approach of numerically solving the equations for the modified long waves is also presented in that article, by assuming that the horizontal flux across a section of flow is some function of the free surface elevation alone. This key assertion is analysed in this article and proved to hold provided some boundedness criteria are satisfied by the flux gradients. The theory is apparently applicable to find appropriate boundedness conditions on the flux of flow for numerically solving long wave equations in the case of other models for long wave propagation as well.

Abstract 5556: An vascularized melanoma model for with unidirectional perfusion of circulating immune cells for advancing immune-oncology research

Abstract Understanding the interactions between the tumor the vascular systems and circulating immune cells is crucial for elucidating mechanisms of immune cell recruitment in cancer and in exploring potential immunotherapeutic approaches. However, current in vitro models often lack the fidelity to replicate these intricate dynamics observed in vivo. The OrganoPlate Graft has been developed for perfusion of peripheral blood mononuclear cells (PBMCs) through a vascular bed with a melanoma monolayer (A375) to study aspects such as immune cell adhesion, extravasation and interaction with the tumor. The OrganoPlate Graft comprises 48 chips per plate, each designed to simulate the conditions of vascular beds. The device achieves flow through passive leveling, utilizing gravity to induce a pressure drop and unidirectional flow across the vascular bed in both positive and negative inclines. This approach avoids the complications and potential artifacts introduced by external pump, reduces complexity, and increases the throughput with up to 16 plates (768 chips) served by each OrganoFlow rocker. In experimental settings, formation of the vascular bed was seen to be consistent in plates and the introduction of the chemokine CXCL-12 led to the establishment of a gradient. Subsequently, PBMCs were observed to localize in clusters as a result of extravasation towards this gradient and the A375 monolayer. This behavior is consistent with known chemotactic responses in more complex in vivo environments. A notable observation was the sustained activity of PBMCs within the system. Cells continued to perfuse through the vascular bed for up to three days after seeding. In summary, the OrganoPlate Graft provides a platform for studying immune interactions in an immunocompetent vascular bed model. Its design and functionality allow for the exploration of immune cell behaviors in proximity to tumor cells, offering potential insights for immune-oncology research. The system's ability to mimic immune cell migration and extravasation in a controlled environment, and future potential to observe tumour killing makes it a valuable tool for advancing our understanding of immune-tumor interactions and may contribute to the development of novel immune-oncology therapeutic strategies. Citation Format: Manuel Caro Torregrosa, Sander de Ruiter, Todd Burton, Karla Queiroz, Will Allen, Job Komen, Sebastiaan Trietsch, Lenie van den Broek. An vascularized melanoma model for with unidirectional perfusion of circulating immune cells for advancing immune-oncology research [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5556.

Numerical investigation of flow patterns in cuttings transport for extended-reach horizontal wells with rotation drillpipe

During the drilling process of extended-reach horizontal wells, the formation of the cuttings bed at the bottom of the wellbore is prone to cause drilling sticking and pump accidents. A coupled method of Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) is used here to study the flow patterns and transition of cuttings transport. Firstly, the model is validated with experimental results, which shows a good agreement. Then, the impact of the rotation speed, eccentricity, and conveying velocity on cuttings flow pattern are analyze. The total Reynolds number is introduced here to established a curve with dimensionless pressure drop, which divides the parameter interval of each flow pattern, and the change rule of cuttings flow pattern is also revealed. This study will establish a theoretical foundation for enhancing borehole cleaning efficiency and hold practical significance in guiding the drilling field construction of extended-reach wells.

From debris bed formation to self-leveling behaviors in core disruptive accident of sodium-cooled fast reactor

Understanding the Core Disruptive Accident (CDA) is crucial for the safety analyses of Sodium-cooled Fast Reactors (SFR), despite its exceedingly low possibility. During a CDA, the potential release and subsequent relocation of molten materials from the core could result in the formation of a debris bed inside the reactor vessel due to their quenching and fragmentation from the interactions with the subcooled sodium coolant. Debris beds with varying shapes are expected to form due to the different flow-regime characteristics during their formation. Further, the heat decay from this high-temperature debris might trigger sodium coolant boiling, instigating the debris bed self-leveling behavior, which flattens the debris beds. Considering the importance of the debris bed shapes to the debris transfer, heat removal and neutronic criticality, lots of knowledge about the mechanisms and characteristics of debris bed formation and self-leveling behaviors has been gathered in recent years through extensive experimental, modeling and numerical outcomes. This study aims to systematically and critically summarize these past explorations into the debris bed formation and self-leveling behaviors, offering a beneficial direction for future research on the improved safety evaluations in SFR severe accidents.

Effects of pellet-sinter interaction parameters on component segregation and bed porosity considering flow velocity and mixture composition: A DEM study

Bed permeability is a crucial factor in blast furnace performance which depends on the material distribution achieved through charging. Since a homogeneous bed of pellet and sinter is recommended, it is crucial to understand whether segregation of the pellet-sinter mixture occurs during charging. The Discrete Element Method is useful in this regard; however, simulations of pellet-sinter mixture charging currently lack credibility since pellet-sinter interaction parameters have not yet been calibrated and validated. Determining pellet-sinter interaction parameters will require significant efforts, so it is useful to know whether mixture segregation and the resulting bed permeability are sensitive to these parameters. In this work, we investigate to what extent the restitution coefficient, sliding friction coefficient and rolling friction coefficient between pellet and sinter affect segregation during bed formation and the resulting permeability in terms of porosity using a simplified charging setup. The investigation is done for different mixture compositions and flow velocities, and analysis settings including sample size and sampling directions. We conclude that all parameters affect segregation and porosity, regardless of the composition and velocity. Hence, all mixture parameters including the interaction parameters between the components must be carefully calibrated when developing a model for predicting permeability.

Failure Analyses on a Flexible Anode Cathodic Protection System in a Station.

Flexible anodes are a common form of anode ground bed for the cathodic protection of buried pipes in station areas, especially in new stations. In most cases, flexible anode ground beds could obtain uniform potential distribution and good protection. However, in the process of operation, there are also failure conditions such as anode body or cable breakage, electronic shorting between anode and pipes and other situations, resulting in poor protection. How to troubleshoot failures has become a difficult problem restricting the application of flexible anodes in actual production. In this paper, the failures of a flexible anode cathodic protection system in a station were assessed and analyzed in detail. The main reasons for the failures were the electronic shorting between the flexible anode and buried pipe in local area and the breaking of a partial flexible anode. The troubleshooting methods for two kinds of failures were explored. By measuring the potentials of both the flexible anode and pipes in different areas and the excavation test, the location of electronic shoring was determined. And through measuring the grounding resistance of the flexible anode and excavation test, the breaking location of the flexible anode was found. By repairing the failure sites, the failed system was restored to normal, which could provide guidance for the failure analyses of the flexible anode cathodic protection system.

Corrigendum to "Bed forms under combined action of waves and wind-driven currents in the remote foreshore of the non-tidal sea" by Magdalena Stella-Bogusz [Oceanologia 65(3) 2023, 484--493. https://doi.org/10.1016/j.oceano.2023.03.001

The author regrets to inform readers that the acknowledgments were incorrectly formulated in the article by M. Stella-Bogusz, "Bed forms under combined action of waves and wind-driven currents in the remote foreshore of the non-tidal sea", and that the Creative Commons license was improperly indicated. The correct content of the acknowledgments is as follows: "The study was sponsored by the Ministry of Education and Science, Poland, under the IBW PAN statutory program No. 2 and by the National Science Centre, Poland, within the research project No. 2021/41/B/ST8/01943 ('Dynamics of Bottom in the Remote Foreshore of the Non-Tidal Sea'), which are hereby gratefully acknowledged." The correct Creative Commons license for the article "Bed forms under combined action of waves and wind-driven currents in the remote foreshore of the non-tidal sea" by M. Stella-Bogusz is CC-BY instead of CC BY-NC-ND.

DESIGN AND VERIFICATION OF THE MODEL OF STRUCTURE FORMATION AND HEAT TRANSFER IN A FLUIDIZED BED APPARATUS WITH A HEAT JACKET

A one-dimensional mathematical model of the formation of a fluidized bed and the evolution of its thermal state during the heating of an ensemble of particles is proposed based on the mathematical apparatus of the Markov chain theory. When describing the thermal state of the system, the processes of interfacial heat exchange between the gas flow and particles, as well as between the wall of the apparatus and the gas suspension, were taken into account. The results of previous studies and known empirical regularities for the material constants of the process were used to identify the parameters of the model. The parametric identification made it possible to adapt and apply the mathematical model for calculating the process of heat treatment of the suspension of silicate sand particles in an apparatus with a fluidized bed of a periodic principle of operation equipped with a heating jacket. Verification of the predictive capabilities of the physicomathematical model adapted in this way was carried out by comparing the forecasts obtained by calculation with the results of the full-scale experiment conducted during the study. To conduct the full-scale experiment, a sample of sand particles was placed in the apparatus, which was previously output to the established thermal regime of operation. After loading the material, a set of thermocouples equidistant from each other was placed in the apparatus and temperature readings were taken at different heights from the level of the gas distributor. The temperature distributions obtained in this way along the bed height were in good agreement with the calculated forecasts and show a significant heterogeneity of the gas phase temperature fields. The temperature of the particles was estimated only as an integral characteristic by measurements of the heat content of the bulk medium after unloading from the apparatus. The integral temperature of the particles also turned out to be close to the predicted values. In addition, during the computational and experimental study, the kinetic characteristics of the heating of the suspension of the material were clarified. Thus, the proposed mathematical model has sufficient predictive efficiency for engineering tasks and can be considered as a basis for constructing a computer method for calculating heat exchangers with a heating jacket using the fluidization technique of bulk media.

Evaluation of Organic Treatments for Enhanced Bioremediation of Crude Oil Impacted Soil in Bayelsa State, Nigeria

The aim of this study was to evaluate organic treatments for enhanced bioremediation of crude oil impacted soil in Bayelsa State, Nigeria. Koroama community in Gbarain clan, Yenagoa local government area, Bayelsa State, Nigeria was randomly selected for the study. The experimental research design was adopted for this study, which was carried out for 28 days. The required soil samples were collected at a depth of 0 – 15cm from a 3 x 3m experimental plot developed in a farmland in Koroama community. Five sampled points, in the form of flat beds A, B, C, D and E respectively were randomly selected. Sampled beds A to D were simulated (contaminated) with 2.25kg of crude oil. The objective is to simulate conditions of a major crude oil spill. The crude oil contaminated soil samples were then allowed to condition for 6 days before treatment with 2kg organic treatments like goat manure (GM), poultry droppings (PD) and the combination of goat manure and poultry droppings (GM & PD). Bed E was unpolluted and untreated (control A) while Bed D was crude oil impacted and untreated soil (control B). The study showed that the impact of crude oil on the soil affects both the physical properties of the soil. The study also showed that the sampled organic treatments were all effective in restoring the physical properties of the crude oil impacted soil. At the end of the study, GM showed the highest TPH degradation rate (62.1%) followed by PD (57.1%) and the least, the combination of GM & PD (52.0%). Hence, the application of GM, PD and the combination of GM & PD are highly recommended for bioremediation of crude of impacted soil with special preference to GM.

A novel transient hole cleaning algorithm for horizontal wells based on drift-flux model

With the continuous expansion of unconventional and offshore oil and gas fields, horizontal wells have become adopted as an economical and effective mining method. However, the inclined and horizontal sections make them prone to cuttings deposition in the wellbore, leading to the formation of a cuttings bed that adversely affects drilling operations. In this paper, we focus on the features of cuttings transport in the wellbore during drilling and propose a solid-liquid two-phase transient flow model by integrating the flow pattern and drift flux model. The model is discretized using a format based on the finite volume method and solved using a preprocessing method. It enables us to predict the flow parameters, cuttings bed distribution, and cuttings removal time in the wellbore of horizontal wells.To validate the model's effectiveness, we verify it using laboratory experimental data, which demonstrates its prediction accuracy. Furthermore, we use the established model to simulate the damage effect of the cuttings bed on the hole cleaning device during drilling. By comparing the complete return time of cuttings under different working conditions, we quantitatively analyze the hole cleaning device's effect and the backreaming operation's cleaning efficiency. The results indicate that the use of hole cleaning devices during drilling, backreaming, well washing, and other operations in the hole cleaning process can effectively suspend the cuttings deposited in the annulus, allowing them to return to the wellhead more quickly, which enhances the cleaning efficiency of the wellbore and reduces the overall construction time. Furthermore, by comparing and analyzing the effect of drilling flow rate, well cleaning flow rate, cutting particle size, temperature gradient and rate of penetration (ROP) on cuttings return efficiency, it was observed that the drilling flow rate and ROP have minimal impact on the time required for complete cuttings removal during drilling. However, cutting particle size has a significant impact on the effective distance of the hole cleaning tool. Meanwhile, the temperature gradient and the flow rate during the well cleaning has a decisive influence on the time needed for complete cuttings removal.

Effect of coolant boiling induced by accumulated debris on flow-regime characteristics of debris bed formation behavior for sodium-cooled fast reactor: Experimental and modeling study with gas injection

Understanding the Debris Bed Formation (DBF) behavior is important to the optimized integral evaluation for Core Disruptive Accident (CDA) of Sodium-cooled Fast Reactor (SFR). Aimed at clarifying the characteristics of flow regimes during DBF, extensive experimental works were carried out by releasing solid particles into a water pool. According to the preliminary studies using bottom heating and nitrogen gas injection, it was found that the effect of coolant boiling should be crucial to the flow-regime transition. However, the gas flow rate considered in these studies (0–50 L/min) was not adequate wide to cover the range of vapor flow rate from the possible drastic boiling in actual CDA of SFR. Therefore, in current study, to elucidate the influence of coolant boiling on DBF flow-regime characteristics more comprehensively and provide more extensive data for supporting the predictive model development, a greater number of experiments are conducted with a much-enlarged range of gas flow rates (up to 100 L/min) under varying parametric conditions (including particle size, particle type, water depth and release pipe diameter). Through analyzing the flow-regime transition, an extended functional form for the effect of coolant boiling is successfully proposed. By incorporating this form into our base model, the model predictability can be extended for the DBF at the conditions of coolant boiling induced by accumulated debris in accordance with the verification of the regime map. Present study is believed to be valuable for further developing and verifying the models and codes for SFR safety analysis in China.

A Review of the Settling Law of Drill Cuttings in Drilling Fluids

During the drilling process, cuttings settle under the action of gravity, which easily results in the formation of a cuttings bed, which then results in wellbore cleaning problems. The settling law of cuttings in drilling fluid is essentially a problem of solid–liquid two-phase settling. This study analyzes and summarizes the effects of the wall effect, the rheology of the fluid, particle shape irregularity, and particle concentration on the settling rate of particles and clarifies the problems faced by current research on the settling rate of particles and the development direction. Studies have shown that walls exert additional blocking effects on particles, thus reducing their settling velocity. The shear thinning effect of non-Newtonian fluids such as power-law fluids and Herschel–Bulkley fluids will reduce the viscosity of the liquid, thus increasing the settling velocity of the particles. Compared with spherical particles, irregular particles will obtain higher resistance in the fluid, leading to a decline in the particle settling velocity. The mutual interference between particles will result in an increase in the drag force on the particles and a decline in the settling velocity. However, when the particles are aggregated, the settling velocity will increase. This study can provide theoretical guidance for predicting the migration law of cuttings during the drilling of horizontal wells, and it has important significance for enriching the theory of solid–liquid two-phase flow.