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A phase-field model can continuously smear sharp cracks into diffusive zones with finite width in which the critical energy release rate is commonly determined as constant. However, such an assumption may be insufficient in the case of rock-like materials since the energy release rate can be different for modes I and II cracks. If not accounted for, this could compromise the accuracy of the correct propagation of both wing and secondary cracks. This study proposes an extended, modified phase-field model for simulating a series of Brazilian discs made of a three-dimensional (3D)-printed rock-like material through a time-independent plane strain model. The phase-field model accounts for the splitting of different energy release rates for modes I and II to capture the complex fracture behavior. The novelty of this study lies in not only the theoretical development of the distinction of surface energy release rates but also the qualitative and quantitative assessment of mixed-mode fracture behaviors, which guarantees good predictive capabilities for the location of crack initiation and the direction of crack propagation in various practical applications. Moreover, the modified phase-field model can be implemented easily and fast without introducing new parameters. The numerical results are first validated against experimental data. The impact of the modified energy release rate on crack propagation, particularly on wing cracks, is then numerically investigated. The results show that wing cracks become more dominated by tensile stresses with a decrease in the ratio of modes I and II energy release rates. The phase-field simulations with the modified energy release rate proposed here can reproduce the experimental results both qualitatively and quantitatively with respect to crack propagation patterns, peak loads, crack coalescence loads and coalescence type.

Understanding the hysteretic behaviour in fluid–fluid displacement processes in porous media is critical in many engineering applications. In this work, we study the quasi-static immiscible displacement process in two-dimensional porous media during cyclic injections in the context of carbon geosequestration. The role of wettability on the residual trapping of CO $_2$ is investigated numerically using an extended interface tracking algorithm. Despite that higher CO $_2$ saturation can be achieved in CO $_2$ -wet porous media after the first CO $_2$ injection, the majority of CO $_2$ is found to be unstable and can be mobilised during subsequent water injection processes. An improvement in the residual trapping of CO $_2$ is observed as the number of injection cycles increases, which is associated with the dispersion of continuous CO $_2$ ganglia into numerous smaller blobs. Compared with either water-wet or CO $_2$ -wet porous media, it is found that less CO $_2$ is trapped within the neutral-wet ones at equilibrium state after a sufficient number of injection cycles. The hysteretic behaviour of saturation between water/CO $_2$ injection cycles is found to follow an exponential decay, which eventually reaches a finite value. This process corresponds to the shift of the mobile region during displacement from typical capillary fingering to a less ramified regime, which ultimately converges towards main flow channels. This work highlights the hysteretic behaviour during cyclic injections, providing insights on the wettability impacts on multiphase flow in porous media, which is of great importance in applications such as carbon geosequestration and geological hydrogen storage.

Abstract Diffusive behaviour is the fundamental mechanism of ionic-induced corrosion in cement–granular composites. Aggregate characteristics, including shape anisotropy, spatial orientation, and size distribution, significantly influence effective diffusivity. However, influences of all such types of aggregate irregularity have rarely been systematically quantified, and most of the representative aggregate shapes in numerical simulations are convex than realistic concave. In this study, we apply the finite element method (FEM) to investigate diffusion behaviour of 2D cement-based composites. Realistic multi-scale aggregate shapes, characterised by fractal dimension (Fd) and relative roughness (Rr), are generated to highlight the influence of aggregate morphology on the effective diffusivity. The spatial distribution is evaluated by the disorder index. From numerical results, samples with a larger disorder index, indicating a broader throat size distribution, show smaller effective diffusivities. Meanwhile, aggregate shape irregularity causes much smaller effective diffusivities, highlighting the necessity of the realistic concave particle shapes in numerical simulations. Sensitivity studies show Fd and Rr are more related to the effective diffusivity than other single-scale classical shape parameters. At last, a model with only these two shape parameters is proposed to predict effective diffusivity. This work further improves the understanding of the role of aggregate morphology on the effective diffusivity, towards applications in ionic-induced corrosion in two-phase composites. Highlights Realistic grain shapes in composites are generated using Fourier transformation. Effects of aggregate characteristics on the effective diffusivity are investigated. Fd and Rr are key geometrical parameters influencing the effective diffusivity.

Particle morphology has great influence on mechanical behaviour and hydro/thermal/electrical conductivities of granular materials. Surface reconstruction and mesh generation are critical to consider realistic particle shapes in various computational simulations. This study adopts the combined finite- discrete element method (FDEM) to investigate single particle crushing behaviour. Particle shapes were reconstructed with spherical harmonic (SH) in both spherical and Cartesian coordinate systems. Furthermore, the reconstructed surface mesh qualities in two coordinate systems are investigated and compared. Although the efficiency of the two SH systems in reconstructing star-like shapes is nearly identical, SH in Cartesian coordinate system can reconstruct non-star-like shapes with the help of surface parameterisation. Meanwhile, a higher triangular mesh quality is generated with spherical coordinate. In single particle crushing tests, the low mesh quality produces more fluctuations on load–displacement curves. The particles with more surficial mesh elements tend to have a lower contact stiffness due to more contact stress concentrations induced by complexity of morphology features and more volumetric tetrahedral elements. The fracture patterns are also influenced by mesh quality and density, e.g. a particle with fewer mesh elements has a simpler fragmentation pattern. This study serves as an essential step towards modelling particle breakage using FDEM with surface mesh directly from SH reconstruction.

Clay minerals and clayey soils have been extensively researched over the last century leading to a rich and still evolving corpus of knowledge on clay chemistry, microstructure and macroscopic behaviour. Clay has the ability, under certain conditions, to spontaneously repair its cracks. However, despite ample evidence, clay self-repair remains understudied and under-theorised. For example, the majority of experimental studies discussing clay self-repair infer its existence from changes to macroscopic properties assumed to be caused by self-repair, and only a small number of studies have attempted to observe self-repair directly. This paper reviews the literature on clay self-repair. First, it situates clay self-repair within the broader context of self-repairing material. Next, autogenous self-repair of clay, under wet-dry cycles, freeze–thaw cycles and deep-ground consolidation, is presented focusing on evidence, driving mechanisms and key variables of influence. Next, theories of clay self-repair proposed in the literature are discussed, highlighting their scope and limitations, as well as the extent to which they have been validated by experimental observations. Key gaps in current knowledge of clay self-repair are highlighted and ways in which they can be addressed in future research are proposed. Finally, a nomenclature distinguishing between different kinds of clay self-repair is proposed based on eight different attributes.

Discrete Element Method (DEM) simulations are carried out to investigate the packing structure of the vibrated mono-sized and polydisperse particle assemblies in slender prismatic containers. Quantities like void fraction distributions, coordination number distribution, Voronoi packing fraction distributions were analyzed. DEM simulations show excellent agreement with the experimental data. The transient response of the packing structure during the vibration of mono-sized spheres reveals that the crystallization starts at the walls. The packing structure's crystallinity enhances during vibration, increasing the packing density of the assembly. Vertical vibration is found to be more effective compared to lateral vibration. The packing structure is found to be independent of the container's orientation during the filling process. The influence of the ratio of the container dimensions to mean particle diameter (X/dm) and polydispersity (λ) on the packing structure is analyzed. The results showed that the increase of X/dm ratio or λ, increases the random arrangement of particles.

The morphological structure of granular materials can dominate their mechanical, hydraulic, electrical, and thermal properties; thus, the formation of order and disorder arrangement of particles is the key characteristic to describe such micro-structures. During the packing procedure, external energy input and perturbations, such as dynamic cyclic load, and the particle size distribution were mentioned by many previous works to be significant in controlling the structure. This study explores order to disorder transition within 2D binary granular assemblies under vibration. A numerical packing method combining particle size growth and dynamic vibration is implemented and verified against experiments to achieve desired packing structure. The Bond orientation order number and pair distribution function are used as indices for characterising the morphological structure. Our packing simulation results show a combination of appropriate vibration and a proper particle size growth rate can facilitate the formation of granular crystallisation. Additionally, for binary packing, the size ratio, and the number fraction of small particles can play a critical role in determining the morphological transformation.

The macroscopic behaviour of an assembly of polydisperse spherical particles is studied using a numerical model based on discrete element method (DEM), which accounts for the microscopic interactions between individual particles and their damage. DEM models particle–particle interactions enabling to understand the influence of microscopic particle–particle interactions on the macroscopic response. The method is used to stimulate the mechanical response of a polydisperse particle assembly under uniaxial compressive load. The influence of damage rate and the initial packing fraction on the macroscopic stress–strain response is investigated. The analysis shows that the initial nonlinear elastic behaviour is influenced by the initial packing factor, whereas the critical stress is influenced by both initial packing fraction and damage rate. It is also observed that critical stress occurs when the assembly reaches a particular damage state. Furthermore, the failure behaviour of different sized particles within a polydisperse assembly is also investigated. The experimental data from the literature show that the crush strength of the particle of given size is observed to vary over a range. Such variation of crush strengths for a given particle size is also implemented in the present work.

International audience; We experimentally investigated the packing of wet monodisperse spheres with controlled falling height. The packing fraction are found to decrease with smaller grain size and free fall heights. A model describing the effects of interparticle force and falling height on packing fraction is developed by introducing a dimensionless length scale, representing the extent of particle rearrangement towards a denser state due to impacts of falling grains. A universal law is observed for both wet particles where capillary forces dominate and dry powders where van der Waals forces govern the packing behaviour. This study deepens the understanding of packing of cohesive spheres and provide a simple experimental method for generating granular media with tailored packing fraction.

Estrogen receptor-positive (ER+) breast cancer (BC) is a common subtype of BC with a relatively good prognosis. However, recurrence and death from ER+ BC occur because of tumor heterogeneity. This study aimed to explore tumor heterogeneity using next-generation sequencing (NGS) and tumor-organoid models to promote BC precise therapy. We collected needle biopsy, surgical excision, and cerebrospinal fluid (CSF) samples to establish tumor organoids. We found that the histological characteristics of organoids were consistent with original lesions and recapitulated their heterogenicity. In addition, the NGS results showed that PIK3CA and TP53 genes had detrimental mutations. BAP1, RET, AXIN2, and PPP2R2A genes had mutations with unknown function. The score for homologous recombination deficiency (HRD) of genome was 56, indicating that the tumor was likely sensitive to PARPi. The mutant-allele tumor heterogeneity (MATH) value of the tumor genome was 68.03, indicating high tumor heterogeneity. At last, we performed a drug screening on organoids. The toxicity of different drugs toward BC organoids originated from needle biopsy and surgical excision was tested, respectively. The IC50 values in the needle biopsy groups were paclitaxel 2.83 μM, carboplatin 61.47 μM, neratinib 0.8 μM, lapatinib >100 μM; in the surgical excision groups: trastuzumab >100 μM, docetaxel 0.036 μM, tamoxifen 20.54 μM, olaparib 5.478 μM, BYL719

The unstable fluid–fluid displacement patterns in porous media with rough invasion fronts and trapping of the defending phase are often observed in drainage, i.e. when the solid is non-wetting to the invading phase. On the other hand, during imbibition, compact and faceted growth is expected in regular porous media with geometrically homogeneous pore structure. Here, we report the irregular growth of invading fluid during the imbibition process in two-dimensional regular porous media. The ramified invasion morphology associated with thin fingers is reminiscent of capillary fingering. Through examining the capillary pressure signals and the type of pore-scale invasion mechanisms, the fundamental differences between faceted growth and irregular invasion are revealed. By analysing the pore-scale invasion mechanisms, a phase diagram describing the dominance of different invasion events is proposed. Through conducting systematic quasi-static radial injection simulations across a wide range of porosity and wettability, excellent agreement is observed on the transition boundary from faceted and compact displacement patterns to irregular and dendritic invasion morphologies. This is reflected by the overlap of the transition boundaries from analytical prediction, type of pore-scale invasion events, and macroscopic morphology quantified by the fractal dimension. This work provides new insights on the role of geometrical features of solid structures during multiphase flow with emphasis on the porosity and wettability. The findings could assist in guiding the design of microfluidic devices to control deterministically the multiphase flow, transport and reaction processes.

The dynamic contact angle of a gas–liquid–solid system depends on the contact line velocity and ignoring this effect could lead to inaccurate estimations of the capillary pressures in microporous media. While most existing coarse-grained molecular dynamics (CGMD) models use one particle to represent a few molecules, we present a novel CGMD framework to model microscale CO2/water flows in silica with each particle representing hundreds of thousands of molecules. The framework can reproduce the densities and viscosities of water and CO2, water–CO2 interfacial tension, and static contact angle over a wide range of pressures. The validated framework is applied to study the velocity-dependency of contact angle of the microscale CO2–water–silica system. The results indicate that the assumption in the molecular kinetic theory that liquid–solid interaction is similar to the reversible work of adhesion between liquid and solid may not hold for CO2–water–silica systems.

Water management remains one of the major challenges in optimising the performance of PEMFCs, in which liquid accumulation and removal in gas diffusion layers (GDLs) and flow channels should be addressed. Here, effects of GDL surface roughness on the water droplet removal inside a PEMFC flow channel have been investigated using the Volume of Fluid method. Rough surfaces are generated according to realistic GDL properties by incorporating RMS roughness and roughness wavelength as the main characteristic parameters. Droplet dynamics including emergence, growth, detachment, and removal in flow channels with various airflow rates are simulated on rough substrates. The influences of airflow rate on droplet dynamics are also discussed by comparing the detachment time and droplet morphology. The liquid removal efficiency subject to different surface roughness parameters is evaluated by droplet detachment time and elongation, and regimes of detachment modes are identified based on the droplet breakup location and detachment ratio. The results suggest that rough surfaces with higher RMS roughness can facilitate the removal of liquid inside flow channel. Whilst surface roughness wavelength is found less significant to the liquid removal efficiency. The results here provide qualitative assessments on identifying the key surface characteristics controlling droplet motion in PEMFC channels.

In this paper, we investigate the initiation and growth of instability patterns arising from the shock loaded internal surfaces of granular rings confined in a Hele-Shaw cell using both experimental and numerical approaches. A variety of patterns are formed in granular media consisting of grains with varying morphologies. When the particle shape becomes increasingly irregular, and/or the gap in the Hele-Shaw cell becomes narrower, it is increasingly hard for confined particles to fluidize. Consequently the emergent pattern transitions from a smooth circle with trivial undulation which grows in a self-similar manner to an unstable finger-like structure with significant tip-splitting. The distinct growth mode of the well-defined instability pattern is closely associated with its inception phase alongside the transmission of the compaction front. The runaway growth of the incipient perturbations gives rise to the unstable growth of the late-time finger-like instabilities. Conversely the minimal growth of the perturbations in the inception phase guarantees the ensuing self-similar growth of the instability patterns featuring insignificant corrugation. The grain-scale simulations reveal the fundamental role played by the heterogeneous non-linear force network inherent to granular media in the stable-to-unstable transition of the instability pattern. The present work reveals the correlation between the grain-scale physics underpinning the formation of surface instability upon shock loading granular media and the nature of the resulting macro-scale instability patterns. The macroscopic flowability of particles through the confined space is found to be the foremost indicator of the nature of the shock induced granular instability pattern.

This paper is investigating the performance of Australian hemp in hempcrete including unretted and retted hurd and fines for wall and render applications, respectively. The mechanical, thermal and acoustic characteristics of hempcrete are assessed including the effect of retting process. Although the retting process caused about 12% decrease in shiv bulk density, which was attributed to the degradation of hemp and a lower solid volume fraction, hempcrete bulk density, mechanical characteristics, thermal conductivity and acoustic performance are not significantly influenced by the retting process. The thermal conductivity appears to be proportional to the bulk density which is proportional to the hemp content of hempcrete. Acoustic performance of wall mix specimens was outstanding with a maximum sound absorption coefficient around 0.90 for a frequency around 700 Hz. However, the acoustic performance of render mix specimens was extremely poor compared to that of wall mix specimens with a sound absorption coefficient less or equal to 0.13. The combined effects of fine particle size and high binder content is responsible for this drastic drop in sound absorption coefficient. Acoustic performance was much more impacted than thermal conductivity by the hemp fine particle size and high binder content of the render mix.

Normal contact behaviour between non-adhesive fractal rough particles is studied using a finite element method (FEM). A series of spherical grain surfaces with distinguished roughness features are generated by means of Spherical Harmonics. These surfaces are described by two roughness descriptors, namely, relative roughness (Rr) and fractal dimension (FD). The contact behaviour of rough spheres with a rigid flat surface is simulated using FEM to quantify the influences of surface structure and sphere morphology by focusing on contact stiffness and true contact area. The dependence of normal contact stiffness (k) on applied normal force (F) is found to follow a power law (k = αFβ) over four orders of magnitude, with both α and β being highly correlated with Rr and FD. With increasing load, the power exponent converges to that of Hertzian contact, e.g., 1/3, independent of Rr. Regions of true contact evolve through the formation of new microcontacts and their progressive merging, meanwhile the area distributions of contact island induced by various forces tend to obey similar Weibull distributions due to fractal nature in their surfaces. Contacts with larger values of Rr are found to produce contact contours with higher fractal dimension as calculated by a 2D box-counting method. Our results suggest that the correlation between radial lengths in a quasi-spherical particle should be considered in studying contact behaviour.

Multiphase flow in porous media is involved in various natural and industrial applications, including water infiltration into soils, carbon geosequestration, and underground hydrogen storage. Understanding the invasion morphology at the pore scale is critical for better prediction of flow properties at the continuum scale in partially saturated permeable media. The deep learning method, as a promising technique to estimate the flow transport processes in porous media, has gained significant attention. However, existing works have mainly focused on single-phase flow, whereas the capability of data-driven techniques has yet to be applied to the pore-scale modeling of fluid–fluid displacement in porous media. Here, the conditional generative adversarial network is applied for pore-scale modeling of multiphase flow in two-dimensional porous media. The network is trained based on a data set of porous media generated using a particle-deposition method, with the corresponding invasion morphologies after the displacement processes calculated using a recently developed interface tracking algorithm. The results demonstrate the capability of data-driven techniques in predicting both fluid saturation and spatial distribution. It is also shown that the method can be generalized to estimate fluid distribution under different wetting conditions and particle shapes. This work represents the first effort at the application of the deep learning method for pore-scale modeling of immiscible fluid displacement and highlights the strength of data-driven techniques for surrogate modeling of multiphase flow in porous media.

In granular media, topological features are known to determine the effective material properties and boundary behavior when interacting with other structural components. X-ray computed tomography results are reported on sphere packing structures in slender prismatic containers (X = 20, Y = Z = 80 mm), filled and vibrated with both monosized spheres (diameter d = 2.4 mm), Exp. (M), and polydisperse spheres (1 mm < d < 1.25 mm), Exp. (P). Packing structures were characterized by void fraction distributions, coordination numbers, contact angle distributions and Voronoi packing fractions. In (M), an almost perfect hexagonal dense packing exists in the total volume, associated with a packing fraction γ t≈0.68. In additional packing experiments, large γ t values were achieved as well. Although the d spread in (P) is relatively small, significantly different results are obtained: γ t≈0.62, regular structures are restricted to narrow wall zones and distributions in the container volume are nonhomogeneous. It is argued that the small degree of ordered structure is a characteristic feature of polydispersity for efficiently vibrated sphere packings.

Magnesium alloys usually lack “operative deformation slip mechanisms” because of their hexagonal close-packed structure. Therefore, the mechanical behavior of magnesium alloys at different temperatures is dictated by other deformation mechanisms such as twinning, detwinning, secondary twinning, or dynamic recrystallization (DRX). Twinning and DRX can affect the development of grain size and orientation distribution, as well as the deformation behavior of magnesium alloys. The current understanding of the mechanisms and mechanics of these different deformation modes and their implementation in crystal plasticity-based modeling are highlighted in this article. Future directions in the development of constitutive models are also discussed.

When particle rings/shells are subjected to divergent explosive loadings, a dual overlapping particle jetting structure emerges during the shock interaction timescale which consists of a large number of minor jets initiated from the external interface at very early instants and a much reduced number of major jets formed from the internal interface at delayed times but overtaking the minor jets in later times. In the present work, the formation of the hierarchical particle jetting pattern is investigated numerically by discrete element method (DEM) coupled with finite element method (FEM), which execute the mechanical calculations of particles and the explosive/detonation gases, respectively. The numerical results find that the external jetting arises from the spallation of an outer layer pulled away by inward propagating rarefaction waves. Meanwhile an inner compact band re-compressed by a secondary shock remains densely packed while expanding outward. The fragmentation of the inner compact particle band, preceding the internal particle jetting, is caused by the profuse spiral shear failures expanding from the inner radius to the outer radius. The resultant jetting structure depends on the shear-band spacing and the grouping of the clockwise and counterclockwise shear bands as well. The former is a function of the bulk characteristics of the inner compact band, especially the resistance to the shear flows. The latter markedly varies with the microstructure of particle packing, especially the structural order. In the highly ordered extreme, the particle ring with global crystalline structure exhibits six groups of shear bands, probably giving rise to around six fragments. By contrast, the grouping of shear bands in the amorphous packing is far from definite, suggesting an increased number of much smaller fragments to be generated. The dual jetting structure would degenerate into a single jetting pattern if the inner compact band manages to entrain all the spall particles before the shear failure occurs. (C) 2019 Elsevier Ltd. All rights reserved.

To model the effective conductivity of the solid and the pore phase of a lithium-ion battery (LIB) we make use of the resistor network method (RN). We recall the scheme on how resistor networks can generally be set up and numerically solved. Furthermore, we explain how this general method can be applied to an assembly of spherical particles where for the individual resistances between touching particles an analytical formula is being used. As a new feature, we use the same scheme to setup resistor networks for the pore phase of an assembly of spherical particles where we propose a simple geometric approach for the calculation of the individual resistances of pore throats. For the validation of this method we created several random particle structures with different size distributions and calculated effective conductivities with both the RN and the finite element method (FEM). On the one hand, the comparison between RN and FEM shows a very good performance of the RN because the mean error lies within 4%. On the other hand, the RN results always lie within the well-known theoretical bounds for the effective conductivity in porous media. As an important aspect, the RN has proven to be highly efficient concerning the computation time and the resource costs.

Multiphase flow through a porous medium involves complex interactions between capillarity, wettability and gravity during drainage process. In contrast to these factors, the effect of pore distribution on liquid retention is less understood. In particular, the quantitative correlation between the fluid displacement and the level of disorder has not yet been established. In this work, we employ direct numerical simulation by solving the Navier–Stokes equations and using volume of fluid method to track the liquid–liquid interface during drainage in disordered porous media. The disorder of pore configuration is characterized by an modified index to capture small microstructural perturbation, which is pivotal for fluid displacement in porous media. Then, we focus on the residual volume and morphological characteristics of saturated zones after drainage and investigate the effect of disorder under different wettability (i.e., the contact angle) and gravity (characterized by a modified Bond number) conditions. Pore-scale simulations reveal that the highly-disordered porous medium is favourable to improve liquid retention and provide various morphologies of entrapped saturated zones. Furthermore, the disorder index has a negative correlation to the characteristic curve index (n) in van Genuchten equation, controlling the shape of the retention characteristic curves. It is expected that the findings will benefit to a broad range of industrial applications involving drainage processes in porous media, e.g., drying, carbon sequestration, and underground water remediation.

In this research paper, smoothed particle hydrodynamics (SPH) with Johnson Holmquist damage model is adopted for modelling of the blast-induced fractures in Barre granite rock. The permeability of the blast-induced rock is then obtained using the implemented finite volume method code in OpenFOAM. It is found that the calculated permeability depends on the direction of fluid flow and with higher value in radial direction than the axial one. This is mainly due to the higher and larger connected pore network in the radial direction. This research work shows that the adopted SPH method along with finite volume method code can be effectively combined to qualitatively and quantitatively predict the fractured network, to analyse geometry of the fractured network, and to calculate the permeability of blast-induced rock.

In this work, an in-house thermal–Discrete Element Method (DEM) code, recently developed at Karlsruhe Institute of Technology to evaluate the heat transfer in ceramic packed pebble beds, was applied to study the thermal behavior of the breeder beds of the European solid breeder blanket concept. The breeder zone of the helium-cooled pebble bed (HCPB) blanket for the Demonstration (DEMO) reactor was considered as the reference model implementing the same materials, applying the related neutronic heating, and simulating the relevant bed thicknesses. The code was used to evaluate the temperature profile generated by the neutronic heating in the thickness of the breeder bed. A column cutout of packed pebbles bounded by upper and bottom walls, representing the cooling plates of the HCPB, was considered as a representative geometry to carry out the work. The implemented three-dimensional network model evaluates the heat transfer inside packed beds through chains of thermal resistances describing the ther...

Dynamic wetting plays an important role in the physics of multiphase flow, and has a significant influence on many industrial and geotechnical applications. In this work, a modified smoothed particle hydrodynamics (SPH) model is employed to simulate surface tension, contact angle and dynamic wetting effects at meso-scale. The wetting and dewetting phenomena are simulated in a capillary tube, where the liquid particles are raised or withdrawn by a shifting substrate. The SPH model is modified by introducing a newly developed viscous force formulation at the liquid–solid interface to reproduce the rate-dependent behaviour of the moving contact line. Dynamic contact angle simulations with the interfacial viscous force are conducted to verify the effectiveness and accuracy of this new formulation. In addition, the influence of interfacial viscous forces with different magnitude on the contact angle dynamics is examined by empirical power-law correlations; the derived constants suggest that the dynamic contact angle changes monotonically with the interfacial viscous force. The simulation results are consistent with experimental observations and theoretical predictions, implying that the interfacial viscous force can be associated with the slip length of flow and the microscopic surface roughness. This work demonstrates that the modified SPH model can successfully account for the rate-dependent effects of a moving contact line, and can be used for realistic multiphase flow simulations under dynamic conditions.

International audience; We experimentally study the drying of loosely packed wet glass beads at low initial water content. The drying rate is found to decrease at the start, corre- sponding to the decreasing rate period controlled by vapor diffusion, followed by a deviation in drying rate from the diffusion limited evaporation. The prop- agation of drying front associated with a sharp saturation gradient is identified through both image analysis and magnetic resonance imaging technique. The drying-induced collapse of granular medium is observed and quantified. The concentrated collapse at the end of drying suggests the existence of liquid in the form of liquid bridges in the apparent dry region until the end of drying process. Collapse event is found to be local, i.e., a clear boundary can be iden- tified for each collapse event, below which the loosely packed medium remains intact. This indicates the existence of a saturation gradient in the apparent dry region. The drying dynamics and collapse statistics suggest that the observed transition of drying regimes is due to Kelvin effect. This work demonstrates for the first time the drying enhancement phenomenon due to Kelvin effect even for grains with size of hundreds of micrometers, and provides insights on the drying process of partially saturated granular materials, especially near the final period of evaporation.

Hypothesis Control of capillary flow through porous media has broad practical implications. However, achieving accurate and reliable control of such processes by tuning the pore size or by modification of interface wettability remains challenging. Here we propose that the flow of liquid by capillary penetration can be accurately adjusted by tuning the geometry of porous media and develop numerical method to achieve this. Methodologies On the basis of Darcys law, a general framework is proposed to facilitate the control of capillary flow in porous systems by tailoring the geometric shape of porous structures. A numerical simulation approach based on finite element method is also employed to validate the theoretical prediction. Findings A basic capillary component with a tunable velocity gradient is designed according to the proposed framework. By using the basic component, two functional capillary elements, namely, (i) flow amplifier and (ii) flow resistor, are demonstrated. Then, multi functional fluidic devices with controllable capillary flow are realized by integrating the designed capillary elements. All the theoretical designs are validated by numerical simulations. Finally, it is shown that the proposed model can be extended to three dimensional designs of porous media