Rigid Particles Research Articles

Drilling Fluid Technology for Horizontal Well in Ecuador Tambococha Oilfield

The Tambococha Block in Ecuador is an oil field with high porosity and high permeability reservoir characteristics, the lower formation is broken and micro-fractures are developed too. For this reason, utilizing Polyalcohol XCS-III and emulsified paraffin G325 as the main two agents, then optimizing other environmentally friendly agents, a strong plugging reservoir protection water-based drilling fluid is formed finally, which is suitable for the Tambococha oil field in Ecuador. The drilling fluid utilizes the synergistic plugging effect of emulsified droplets, cloud point effect, micron particles and rigid particles to reduce the oil-water interfacial tension and prevent the drilling fluid from entering the formation to finally achieve the purpose of anti-collapse plugging and reservoir protection. Laboratory experiments show that the drilling fluid has strong inhibitory properties, and the linear expansion rate of cuttings in it is reduced by 64.8% compared with that in clean water; the plugging performance is good, and its particle size distribution can fit the ideal filling curve better; the damage to reservoir is a little, with an average damage rate of 10.25% to the cores of the U layer of the Napo formation; the drilling fluid has good environmental performance, and the content of heavy metals meets the requirements of sewage discharge standards. The drilling fluid system has been successfully applied to 15 horizontal wells in the Tambochocha Oilfield. The main performance is with wellbore stability and smooth tripping. The average daily crude oil output of a single well neers 300 t, which is nearly 90% higher than that of offset wells, and the environmental indicators of drilling fluid and drilling cuttings meet the requirements of EPA1311 standards. The research results show that the water-based drilling fluid can meet the drilling safety and reservoir protection requirements of horizontal wells of the Tambococha oil field in Ecuador.

Transient and steady shear rheology of particle-laden viscoelastic suspensions

We study the transient and steady shear rheology of rigid particle suspensions in Boger fluids via complete 3D numerical simulations and experiments. We calculate the transient per-particle extra viscosity and primary stress coefficients for suspensions at different particle volume fractions ϕ for a range of Weissenberg numbers (Wi). The per-particle viscosity ( ηp) and the primary normal coefficient ( ψ1p) increase monotonically to steady state in body-fitted (BF) simulations (for dilute suspensions) and immersed boundary (IB) simulations (for nondilute suspensions). We also present experimental measurements including small amplitude oscillatory shear, steady shear, and transient shear measurements at different particle volume fraction suspensions in a Boger fluid. The simulations and experiments suggest that longer strains are needed to achieve steady state at higher ϕ and Wi. We also show the comparison of the BF and the IB simulations with experimental data for the per-particle viscosity and find excellent quantitative agreement between simulations and experiments at Wi=3 but the IB simulations underpredict the steady values at higher Wi=6. Nevertheless, the IB simulations show an increase in the per-particle viscosity with ϕ as witnessed in the experiments. To understand this behavior, we examine the particle-induced fluid stress (PIFS) and the stresslet contributions using a novel method developed for the IB simulations in this work. We find that the PIFS is independent of ϕ but the stresslet values increase with ϕ. Thus, the particle-particle hydrodynamic interactions in nondilute suspensions affect the stresslet and, in turn, the per-particle viscosity at a given Wi.

Drag and lift forces on a rigid sphere immersed in a wall-bounded linear shear flow

Drag and lift forces experienced by a rigid spherical particle translating close to a flat wall in a linear shear flow are determined through fully resolved simulations. Particles are assumed to obey either a non-rotating or a torque-free condition and may either lead the fluid or lag behind it. The simulations cover a wide range of flow regimes, from low-but-finite Reynolds numbers to conditions close to the onset of wake unsteadiness. Results are used to build accurate semiempirical expressions for the two force components valid at arbitrary Reynolds number, relative shear rate, and separation distance from the wall.

A systematic study on the synergistic effects of MWCNTs and core\u2013shell particles on the physicomechanical properties of epoxy resin

Here, core–shell impact modifier particles (CSIMPs) and multiwalled carbon nanotubes (MWCNs) were used as reinforcing agents for improving the toughness and tensile properties of epoxy resin. For this purpose, emulsion polymerization technique was exploited to fabricate poly(butyl acrylate-allyl methacrylate) core-poly(methyl methacrylate-glycidyl methacrylate) shell impact modifier particles with an average particle size of 407 nm. It was revealed that using a combination of the prepared CSIMPs and MWCNTs could significantly enhance the toughness and tensile properties of the epoxy resin. Also, it was observed that the dominant factors for improving the fracture toughness of the ternary composites are crack deflection/arresting as well as enlarged plastic deformation around the growing crack tip induced by the combination of rigid and soft particles. The Response Surface Methodology (RSM) with central composite design (CCD) was utilized to study the effects of the amounts of CSIMPs and MWCNTs on the physicomechanical properties of the epoxy resin. The proposed quadratic models were in accordance with the experimental results with correlation coefficient more than 98%. The optimum condition for maximum toughness, elastic modulus, and tensile strength was 3 wt% MWCNT and 1.03 wt% CSIMPs. The sample fabricated in the optimal condition indicated toughness, elastic modulus, and tensile strength equal to 2.2 MPa m1/2, 3014.5 MPa, and 40.6 MPa, respectively.

Effect of spatial filter features on local heat transfer coefficients obtained from particle-resolved simulations of a flow through a fixed random array of rigid spherical particles

We use Particle-Resolved (Direct Numerical) Simulation (PR-DNS or PRS) to investigate momentum and heat transfer in the incompressible flow of a Newtonian fluid through a fixed bed of mono-disperse spheres. We perform a set of simulations with various porosities ranging from 0.5 to 0.9, Reynolds numbers ranging from 18 to 72 and Prandtl numbers ranging from 1 to 5 and analyze computed results. All cases are hence in the moderately convection dominated thermal regimes, i.e., Peclet numbers from 18 to 360. We locally average fluid flow data around particles using different filters centered at each particle mass center and we study the effect of the mathematical form of the filter as well as of the filter support size on the particle Nusselt number distribution. While both mathematical form and support size have a limited effect on the average particle Nusselt number, the width of the distribution, i.e., the standard deviation, is strongly influenced by the filter support size. This observation has important consequences for the derivation of new transfer coefficient models that incorporate information about the actual particle microstructure and attempt to estimate the transfer coefficient fluctuations for a given average local porosity.

Acoustic radiation force on a rigid cylinder near rigid corner boundaries exerted by a Gaussian beam field

Acoustic manipulation is one of the well-known technologies of particle control and a top research in acoustic field. Calculation of acoustic radiation force on a particle nearby boundaries is one of the critical tasks, as it approximates realistic applications. Nevertheless, it is quite difficult to solve the problem by theoretical method when the boundary conditions are intricate. In this study, we present a finite element method numerical model for the acoustic radiation force exerting on a rigid cylindrical particle immersed in fluid near a rigid corner. The effects of the boundaries on acoustic radiation force of a rigid cylinder are analyzed with particular emphasis on the non-dimensional frequency and the distance from the center of cylinder to each boundary. The results reveal that these parameters play important roles in acoustic manipulation for particle-nearby complicated rigid boundaries. This study verifies the feasibility of numerical analysis on the issue of acoustic radiation force calculation close to complex boundaries, which may provide a new idea on analyzing the acoustic particle manipulation in confined space.

Fourier reconstruction for diffraction tomography of an object rotated into arbitrary orientations

In this paper, we study the mathematical imaging problem of optical diffraction tomography (ODT) for the scenario of a microscopic rigid particle rotating in a trap created, for instance, by acoustic or optical forces. Under the influence of the inhomogeneous forces the particle carries out a time-dependent smooth, but irregular motion described by a set of affine transformations. The rotation of the particle enables one to record optical images from a wide range of angles, which largely eliminates the ‘missing cone problem’ in optics. This advantage, however, comes at the price that the rotation axis in this scenario is not fixed, but continuously undergoes some variations, and that the rotation angles are not equally spaced, which is in contrast to standard tomographic reconstruction assumptions. In the present work, we assume that the time-dependent motion parameters are known, and that the particle’s scattering potential is compatible with making the first order Born or Rytov approximation. We prove a Fourier diffraction theorem and derive novel backpropagation formulae for the reconstruction of the scattering potential, which depends on the refractive index distribution inside the object, taking its complicated motion into account. This provides the basis for solving the ODT problem with an efficient non-uniform discrete Fourier transform.

Clays in Cosmetics and Personal-Care Products

AbstractClays are used in various cosmetic formulations, such as sunscreens, toothpastes, deodorants, creams, hair cosmetics, makeups, nail polish, facial masks, and shampoos, among others, to improve the organoleptic and physicochemical characteristics, to increase the stability, or to facilitate elaboration. Together with their technological functionalities, clays are cosmetologically active ingredients with cleaning, anti-aging, anti-wrinkling, and sun-care functionalities. Talc, kaolinite, mica, and some smectites are the clay minerals used most frequently in cosmetic products, but several other phyllosilicates as well as modified and synthetic clays are also used. Sometimes, clays are useful in the design of cosmetics just because they are made of rigid, small, and anisometric particles. Kaolinite and mica are made of hard prismatic particles which are lightly abrasive over the skin, teeth, or hair. Electric charges in smectites result in ion-exchange capacities useful in the loading of active cosmetics but also adsorbing and cleaning waste substances. Intermediate net negative charges of smectites result in layer expansion in polar media and specific rheological properties that are very useful in cosmetic formulations. The absence of charged particles in talc and kaolin make them flow easily resulting in lubricant effects. Protection against radiation from the sun by clay particles and decorative effects complete the possibilities of clays in cosmetics. The nomenclature for clays used as ingredients in cosmetics follows historical use and the names of commercial products, rather than following strict compositional principles. In this sense, an effort was made here to correlate the names of the minerals that make up each of the clay-based cosmetic ingredients.

Convergence of the method of reflections for particle suspensions in Stokes flows

We study the convergence of the method of reflections for the Stokes equations in domains perforated by countably many spherical particles with boundary conditions typical for the suspension of rigid particles. We prove that a relaxed version of the method is always convergent in H ˙ 1 under a mild separation condition on the particles. Moreover, we prove optimal convergence rates of the method in W ˙ 1 , q , 1 < q < ∞ and in L ∞ in terms of the particle volume fraction under a stronger separation condition of the particles.

Dualistic effect of Kraft lignin on the viscoelastic behavior of biodegradable biobased PBSA

Lignin is an abundant and low-cost renewable feedstock. In this investigation Kraft lignin was incorporated into the biodegradable poly(butylene succinate-co-adipate), PBSA, using a co-rotating twin-screw extruder to produce films. Lignin content varied from 2.5 to 15 wt% and two extrusion conditions were investigated. The influence of processing conditions and lignin content on PBSA degradation, mechanical and viscoelastic properties were assessed by size exclusion chromatography (SEC), tensile tests, parallel plate rheometry (steady state and oscillatory) and dynamic mechanical thermal analysis (DMTA). The thermal behavior of neat Kraft lignin was assessed by differential scanning calorimetry (DSC). The results suggest that lignin influenced the viscoelastic properties of PBSA differently as a function of temperature and lignin dispersion. Lignin may behave as a rigid particle and have a reinforcing effect on PBSA when significantly below the glass transition temperature (Tg), but gradually transition to a lubricant as the temperature is increased and molecular relaxation occurs.

Influence of rigid particles on thermal conductivity enhancement of polydimethylsiloxane composite during spatial confining forced network assembly

AbstractIn order to meet the heat dissipation requirements of electronic equipment, a variety of methods for preparing thermally conductive polymer composites have been proposed. In this article, highly thermal conductive polydimethylsiloxane (PDMS) composites were prepared by combining the spatial confining forced network assembly (SCFNA) method with adding rigid particles (RPs). The orthogonal experiments were designed to verify the effects of short carbon fiber (SCF) content, glass bubble (GB) content, GB particle size and composite thickness on the thermal conductivity (λ) of SCF‐GB/PDMS composite. In addition, the λ and shapes of different RPs (including GB, SiO2, AlN, glass fiber [GF]) also play vital roles in λ enhancements of SCF‐RP/PDMS composites. The mechanical properties of SCF‐RP/PDMS composites were different with various RPs contents, and the SCF‐GB/PDMS composite presented the largest elongation at break (70%) and the best mechanical flexibility. The SCF‐GB/PDMS composite with a low GB content of 5 vol% can not only greatly improve the λ, but also ensure its excellent mechanical properties.

Computational investigation for endocytosis of CoVID-19 virus SARS-CoV-2 in cell membrane

CoVID-19 virus SARS-CoV-2 follows the endocytosis process to enter inside a cell to infect it. It is important to study the endocytosis of SARS-CoV-2 in cell membrane to prevent the pandemic of CoVID-19. In this paper we develop a finite element based computational model for endocytosis of SARS-CoV-2 in cell membrane and determine curvature generation on it during the process. The virus SARS-CoV-2 is modeled as a rigid spherical particle and cell membrane as an anisotropic elastic material, while its fluidic nature due to lipid exchange with infinite reservoir is preserved using suitable conditions. With the help of a contact pair created between the virus particle and cell membrane, endocytosis process is computationally studied and the curvature of membrane is evaluated as the time progresses during the endocytosis process. At the tip of the virus particle and half-radius distance from it, the membrane follows the curvature of virus very quickly. However, it takes more time for the membrane point located at a distance equal to the radius of the virus particle. This is compensated by the cytoplasmic peripheral proteins binding onto the inside surface of the cell membrane. The role of cytoplasmic peripheral BAR proteins is investigated by using a linear curvature-coupling model with protein concentrations. It is observed that F-BAR protein is more sensitive to the curvature of virus particle in comparison to the other BAR proteins. The sensitiveness deteriorates as the curvature is increased.

The Influence of Reservoir Composition on the Pore Structure of Continental Shale: A Case Study from the Qingshankou Formation in the Sanzhao Sag of Northern Songliao Basin, NE China

Determining the pore structure characteristics and influencing factors of continental shale reservoir in the oil generation stage is of great significance for evaluating the shale oil reservoir space and analyzing shale oil enrichment mechanism. In this paper, shale from the first member of the Upper Cretaceous Qingshankou Formation (K2qn1) in the Songliao Basin was selected. X-ray diffraction (XRD), Rock-Eval pyrolysis, total organic carbon content (TOC), scanning electron microscopy (SEM), nitrogen gas adsorption (N2GA), and high-pressure mercury injection (HPMI) were used to clarify the composition characteristics of inorganic minerals and organic matter and determine the influencing factors of pore development in the K2qn1 shale. The results show that intergranular pores related to clay minerals and quartz, intragranular dissolution pores related to feldspar, and other mineral intragranular pores are developed. The organic matter pore is less developed, mainly composed of intragranular pores and crack pores of organic matter. Mesopores related to clay minerals are widely developed, rigid quartz particles can protect and support mesopores and macropores, and carbonate cementation can inhibit pore development. Although the TOC contents of shale are commonly less than 2.5%, it has a good positive correlation with porosity; TOC is greater than 2.5%, and the increase of residual oil fills part of the pores, leading to a decrease in porosity with the increase of TOC. Three types (types I, II, and III) of the reservoir space were classified by the combined pore size distribution diagram of N2GA and HPMI. By comparing the characteristics of pore structure parameters, it is found that Type I reservoir space is favorable for shale oil enrichment. It provides scientific guidance for shale oil exploration in the Songliao Basin.

Contact between rigid convex NURBS particles based on computer graphics concepts

In the discrete element method (DEM), the geometric description of each particle is important for the overall system behavior. However, increasing complexity of particles also augments the cost for contact detection and its forthcoming evaluation, increasing the computational cost of the numerical simulation. In the context of master-to-master contact, the present work proposes a new formulation for solving the local contact problem between convex particles whose boundary is defined by non-uniform rational B-splines (NURBS). The proposed formulation is based on concepts employed in computer graphics: Minkowski sum, configuration space obstacle (CSO) and support mapping. With that, contact can be addressed through an optimization scheme. An objective function is based on a constrained distance between the particles. In case of contact, the maximum penetration between particles is related to the minimum of the objective function. Different examples underline the robustness of the formulation, which can handle contact between convex particles with general shapes.

Comparison of Continuum Stresses in Granular Material Computed by Volume Average Approach and Boundary Average Approach Under Static and Quasi-Static Conditions

Averaging approaches have been widely used to estimate continuum stress in granular materials to facilitate the assimilation of granular materials’ behavior into a continuum mechanics framework. At present, selection criteria for the appropriate averaging approach are still poorly understood. This paper compares the stresses computed by two popular averaging approaches, i.e., volume average approach (VAA) and boundary average approach (BAA) in order to investigate relative errors between the two approaches under various conditions. The comparisons between VAA and BAA under a static condition were first carried out based on the rigid particle analytical framework proposed by Rothenburg, L. [1980] “Micromechanics of idealized granular systems,” Ph.D. thesis, Carleton University, Ottawa, followed by discrete element modelling (DEM) simulations using PFC3D under a quasi-static condition. The results of theoretical comparison suggested that the relative error in the computed stresses by VAA with an omission of overlap could be grossly estimated by the ratio of overlap to length of contact branch, while the relative error in the computed stresses by VAA with an omission of external contacts could be grossly estimated by the ratio of maximum particle diameter to specimen size. At the ratio of maximum particle diameter to specimen size of 5, which is usually taken as the minimum recommended ratio to minimize boundary effect, the relative error caused by omitting the external contacts was as high as 20%. Numerical comparisons suggested that the relative errors of the two approaches under a quasi-static condition were significantly influenced by the strain energy ratio defined in this study. The VAA was recommended as a preferred computation method over the BAA when the strain energy ratio was considerably lower than unity.

Lattice Boltzmann simulations of drying suspensions of soft particles.

The ordering of particles in the drying process of a colloidal suspension is crucial in determining the properties of the resulting film. For example, microscopic inhomogeneities can lead to the formation of cracks and defects that can deteriorate the quality of the film considerably. This type of problem is inherently multiscale and here we study it numerically, using our recently developed method for the simulation of soft polymeric capsules in multicomponent fluids. We focus on the effect of the particle softness on the film microstructure during the drying phase and how it relates to the formation of defects. We quantify the order of the particles by measuring both the Voronoi entropy and the isotropic order parameter. Surprisingly, both observables exhibit a non-monotonic behaviour when the softness of the particles is increased. We further investigate the correlation between the interparticle interaction and the change in the microstructure during the evaporation phase. We observe that the rigid particles form chain-like structures that tend to scatter into small clusters when the particle softness is increased. This article is part of the theme issue 'Progress in mesoscale methods for fluid dynamics simulation'.

Using a deep neural network to predict the motion of underresolved triangular rigid bodies in an incompressible flow

AbstractWe consider nonspherical rigid body particles in an incompressible fluid in the regime where the particles are too large to assume that they are simply transported with the fluid without back‐coupling and where the particles are also too small to make fully resolved direct numerical simulations feasible. Unfitted finite element methods with ghost‐penalty stabilization are well suited to fluid‐structure‐interaction problems as posed by this setting, due to the flexible and accurate geometry handling and for allowing topology changes in the geometry. In the computationally underresolved setting posed here, accurate computations of the forces by their boundary integral formulation are not viable. Furthermore, analytical laws are not available due to the shape of the particles. However, accurate values of the forces are essential for realistic motion of the particles. To obtain these forces accurately, we train an artificial deep neural network using data from prototypical resolved simulations. This network is then able to predict the force values based on information which can be obtained accurately in an underresolved setting. As a result, we obtain forces on very coarse and underresolved meshes which are on average an order of magnitude more accurate compared with the direct boundary‐integral computation from the Navier–Stokes solution, leading to solid motion comparable to that obtained on highly resolved meshes that would substantially increase the simulation costs.

Inertial and viscous flywheel sensing of nanoparticles

Rotational dynamics often challenge physical intuition while enabling unique realizations, from the rotor of a gyroscope that maintains its orientation regardless of the outer gimbals, to a tennis racket that rotates around its handle when tossed face-up in the air. In the context of inertial sensing, which can measure mass with atomic precision, rotational dynamics are normally considered a complication hindering measurement interpretation. Here, we exploit the rotational dynamics of a microfluidic device to develop a modality in inertial sensing. Combining theory with experiments, we show that this modality measures the volume of a rigid particle while normally being insensitive to its density. Paradoxically, particle density only emerges when fluid viscosity becomes dominant over inertia. We explain this paradox via a viscosity-driven, hydrodynamic coupling between the fluid and the particle that activates the rotational inertia of the particle, converting it into a ‘viscous flywheel’. This modality now enables the simultaneous measurement of particle volume and mass in fluid, using a single, high-throughput measurement.

Leveraging Elasticity to Uncover the Role of Rabinowitsch Suspension through a Wavelike Conduit: Consolidated Blood Suspension Application

The present work presents a mathematical investigation of a Rabinowitsch suspension fluid through elastic walls with heat transfer under the effect of electroosmotic forces (EOFs). The governing equations contain empirical stress-strain equations of the Rabinowitsch fluid model and equations of fluid motion along with heat transfer. It is of interest in this work to study the effects of EOFs, which are rigid spherical particles that are suspended in the Rabinowitsch fluid, the Grashof parameter, heat source, and elasticity on the shear stress of the Rabinowitsch fluid model and flow quantities. The solutions are achieved by taking long wavelength approximation with the creeping flow system. A comparison is set between the effect of pseudoplasticity and dilatation on the behaviour of shear stress, axial velocity, and pressure rise. Physical behaviours have been graphically discussed. It was found that the Rabinowitsch and electroosmotic parameters enhance the shear stress while they reduce the pressure gradient. A biomedical application to the problem is presented. The present analysis is particularly important in biomedicine and physiology.

Alignment of a flexible platelike particle in shear flow: Effect of surface slip and edges

Rigid plate-like particles displaying interfacial slip can attain a constant orientation in a shear flow when the slip length is sufficiently large. But actual thin particles such as single-layer graphene are prone to bending deformations when exposed to shear stress. To study the effect of bending deformation on the particle's stable orientation, we develop a two-dimensional fluid-structure interaction model. We find that (i) a stable alignment occurs even for relatively flexible particles, and that (ii) edges effects on the shape of the plate are important for values of the length-to-thickness aspect ratio as large as 100.