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This article presents a novel two-dimensional quadrilateral solid finite element model, enhanced by incompatible modes and embedded strong discontinuity for simulation of localized failure in quasi-brittle heterogeneous multi-phase materials. The focus of interest lies in the development of discontinuities and cracks induced by both tensile and compressive loads, considering mesoscale material constituents and very complex meshes. Multiple cracks are initiated within elements using local Gauss-point criteria for crack initiation. Rankine and Maximum shear stress criteria control the crack initiation, location, and orientation depending solely on the stress state within the finite element. The model identifies distinct clusters of cracked elements and merges them into continuous cracks. A tracking algorithm ensures crack continuity, eliminating spurious cracks ahead of the crack tip to prevent crack arrest and stress locking. This approach ensures the formation of various types of cracks within the constituents of composite materials and their spontaneous coalescence forming the final failure mechanisms. The constitutive model for the crack representation is the damage softening model, which accounts for opening and sliding behavior. The efficacy of the proposed model is demonstrated through numerical simulations of heterogeneous 3-phase and 4-phase composites subjected to both tensile and compressive load cases. [ABSTRACT FROM AUTHOR]

Rubber concrete (RC) has been used in fatigue-resistant components due to its durability, yet the numerical simulation of its fatigue properties remains in its early stages. This study proposes a cohesive zone model (CZM) that accounts for the accumulation of fatigue damage at the mesoscale to investigate the fatigue performance of RC. The model integrates static and fatigue damage in the CZM, effectively capturing damage caused by fatigue loading. Validation was conducted using experimental data from the existing literature. Based on this validation, four concrete beams with varying rubber replacement rates (0%, 5%, 10%, and 15%) were tested. The CZM was employed to describe the mechanical behavior of the interface transition zones (ITZs) and the mortar interior, which were simulated and analyzed under different stress levels. The results demonstrate that the model accurately simulates crack propagation paths, interface damage evolution, and the fatigue life of RC beams under fatigue loading. A functional relationship between fatigue life and stress level was established for various rubber replacement rates. This study provides a reference model for numerical simulations of RC under fatigue loading conditions and introduces new approaches for analyzing the fatigue performance of other materials. [ABSTRACT FROM AUTHOR]

The key to the modification of the properties of carbon fibers is to understand how to control the structure of polyacrylonitrile-based precursors. Results of a mesoscale modeling of the structure formation processes in a mixture of polyacrylonitrile, dimethyl sulfoxide, and water (good and poor solvents for polymers) are reported. The system′s composition is chosen using the composition of precursor fibers at the later formation stages under coagulation bath conditions. All calculations are performed using the dynamic density functional theory. The proposed model considers effects caused by changes in the system composition, carbon nanotube filler, temperature, and shear flow. It is shown that the polymer structure can be significantly changed by varying the amount of water in the system (determined by the coagulation bath composition) and by introducing a carbon filler. [ABSTRACT FROM AUTHOR]

To bridge the gaps between meteorological large‐eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city‐block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long‐ and short‐wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry‐mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three‐dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology. Plain Language Summary: This study introduces a new multi‐scale urban climate model, City‐LES, which is a hybrid model combining meteorological modeling and engineering computational fluid dynamics (CFD) approaches. This model simulates urban climates across both mesoscale (city scale) and microscale (city‐block scale). Developed through collaboration among urban climatologists, CFD modeling researchers, and high‐performance computing experts, City‐LES simulates airflow in urban areas, conducts three‐dimensional radiation calculations in the urban canopy, incorporates various atmospheric physics schemes, and operates on supercomputers equipped with graphics processing units, as well as CPUs. Furthermore, the model enables the assessment of the efficacy of heat stress mitigation measures such as dry‐mist spraying, roadside trees, cool pavements, and green/cool roof strategies. Validation results indicate that City‐LES accurately simulates urban atmospheric dynamics, the thermal environment, and heat stress indices. The model will serve as a valuable community tool for both fundamental and applied studies in urban climatology. Key Points: This study introduces a multi‐scale urban climate model that combines meteorological and computational fluid dynamics modeling approachesThe model resolves buildings, simulates 3D airflow and radiation in urban areas, and runs on supercomputers equipped with graphics processing units and/or CPUsThe model accurately simulates urban atmospheric dynamics, thermal environments, and heat stress indices [ABSTRACT FROM AUTHOR]

Microcapsule-based self-healing cementitious composite (MSCC) offers autonomous damage repair, extending the service life of structures. However, most of the existing studies focus on static behavior and healing effectiveness but rarely explore dynamic responses. This study developed the mesoscale modeling approach to investigate MSCC behavior under dynamic split tensile loading. At the mesoscale, MSCC can be treated as a four-phase composite consisting of coarse aggregates, interfacial transition zones, cement mortar, and microcapsules. Alternatively, it can be simplified as a two-phase composite comprising a homogeneous mortar matrix and microcapsules. Four-phase and two-phase mesoscale MSCC models were developed for 2D simulations, while a two-phase 3D model was also developed for comparison. Mesoscale numerical simulations were conducted based on Split-Hopkinson Pressure Bar Brazilian disk-splitting tests, considering various strain rates. Simulation results of different mesoscale models were compared with experimental results. All of the models accurately predicted the tensile strength of MSCC, with the 2D four-phase model providing the best representation of failure modes and crack propagation. Both experimental and numerical data exhibited obvious strain rate effects, indicating that MSCC's mechanical properties were sensitive to the loading rate. Dynamic increase factors were obtained, quantifying rate sensitivity. The obtained dynamic mechanical properties of MSCC provide insights for designing MSCC components and structures that can better withstand collisions or explosions. [ABSTRACT FROM AUTHOR]

Microcapsule-based self-healing concrete (MSC) has been widely studied, with a focus on static behavior and self-healing effectiveness. However, the dynamic mechanical properties of MSC have rarely been studied. This study presents a mesoscale numerical investigation of the dynamic compressive behavior of MSC under impact loading. In mesoscale, MSC is regarded as a four-phase composite material mainly composed of coarse aggregates, interface transition zones, cement mortar, and microcapsules. A pseudo 3D numerical model is constructed by combining a slice of a detailed mesoscale model with a homogenous 3D model. The mesoscale MSC slice models with different mass fractions of microcapsules (0%, 2%, 5%, and 8%) are constructed. Different coarse aggregate shapes (i.e., circles, ellipses, and polygons) are considered. The uniaxial dynamic compressive behaviors of MSC materials under loads of different strain rates are numerically simulated and compared with those from split Hopkinson pressure bar tests previously done by the authors. The comparison results show that the present mesoscale model can accurately predict the compressive strength and failure mode of MSC. The effects of the microcapsules ratio and strain rate on the dynamic strength are studied. Results show that the MSC compressive strength decreases with the increase in microcapsules and increases with the increase in strain rate. The dynamic increase factor (DIF) of the specimen is jointly contributed by the material DIF, inertial constraints, and heterogeneity. Different aggregate shapes have little effect on the simulation results of MSC behavior. The obtained dynamic mechanical properties of MSC may assist in designing MSC to resist collisions or explosions. [ABSTRACT FROM AUTHOR]

The design of block‐copolymer‐based functional materials, including mesoporous membranes and nanoparticles, requires a comprehensive understanding of the hierarchical assembly of block copolymers in selective solvents into micelles and subsequent ordered phases. It is hypothesized that micellar ordering and characteristic assembly can be described using a set of phase parameters that account for entropic and enthalpic interactions. Dissipative particle dynamics (DPD) simulations are used to systematically investigate the self‐assembly of semidiluted block copolymers, resembling isoporous membrane preparation conditions. The effect of Flory–Huggins interaction parameters, block lengths, and concentration on the morphology and polydispersity of the micelles is evaluated. The interaction parameters are mapped into Flory–Huggins theory by considering the block's conformation. These results reveal the effect of polymer concentration and solvent affinity on the morphological transition of the aggregates, in agreement with existing experimental evidence. It is identified that monodisperse‐spherical micelles in solution are fundamental to stabilize ordered states. Weak solvent segregation of the largest block, curvature of the core‐corona interface, and stretching of the corona‐forming one are found to be key to stabilize monodisperse assemblies. These conditions can be predicted using spherical‐micelles packing considerations and a global phase parameter from the Flory–Huggins theory. This study provides valuable insights into the self‐assembly of diblock copolymers and offers a potential way to optimize the preparation of mesoporous ordered structures and micelle ordering in semidiluted systems. [ABSTRACT FROM AUTHOR]

The alkali–silica reaction (ASR), a major cause of cracks in concrete, is a critical issue in the maintenance of social infrastructure. In this study, a concrete mesoscale model was meticulously developed, and a coupled stress–moisture model was also developed to reproduce ASR degradation. The aim was to investigate the effect of ASR degradation on the bending load-carrying capacity of RC beams. The concrete mesoscale model, specifically designed to reproduce ASR degradation, was modeled from three phases: coarse aggregate, mortar, and ITZ (interfacial transition zone). ASR was considered as the expansion of the coarse aggregate, and the objective was to reproduce expansion cracks with numerical analysis using the mesoscale model. Uniaxial compression tests were carried out on cylindrical specimens with ASR-accelerated deterioration to clarify the relationship between ASR deterioration and compressive properties, and the experimental results were used to identify material parameters in the mesoscale analysis model. The results showed that the model proposed in this study can reproduce the change in compressive properties due to expansion cracking. Finally, RC beams were constructed using the mesoscale model, and the effect of ASR degradation on the bending load-carrying capacity of the RC beams was investigated. The results showed that the presence of expansion cracks caused the initial stiffness of the load-displacement curves to decrease, but the bearing capacity tended to increase. This suggests that factors other than cracks, such as chemical prestress and boundary conditions in this model, have a strong influence on the load-bearing capacity of deteriorated RC beams. [ABSTRACT FROM AUTHOR]

The paper describes the configuration of the COSMO-Ru6Sib system with a horizontal grid spacing of 6.6 km adapted to regional conditions. The COSMO-Ru2Sib configuration with a horizontal grid spacing of 2.2 km is also considered. The results of modifying this configuration using weather radar data assimilation as well as urban canopy parameterization are presented and discussed. The results of numerical experiments for the COSMO-Ru6Sib with the COSMO and ICON-LAM models as compute kernels are also presented. [ABSTRACT FROM AUTHOR]

Abstract To bridge the gaps between meteorological large‐eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city‐block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long‐ and short‐wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry‐mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three‐dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.

Recent experimental findings have shown that tantalum single crystals display strong anisotropy during Taylor impact testing in stark contrast to isotropic deformation in polycrystalline counterparts. In this study, a coupled dislocation dynamics and finite element model was developed to simulate the complex stress field under dynamic loading of a Taylor impact test and track the intricate evolution of the dislocation microstructure. Our model allowed us to investigate detailed motion of dislocations and their mutual interactions and the effect of varying simulation parameters, such as sample size, initial dislocation density, crystallographic orientation, and temperature. Simulation results show good agreement with experimental observations and shed light on the mechanical response at small-scale under extreme loading conditions. In addition, resolved shear stress analysis incorporating the effect of shear stress from impact was performed to quantitatively support and provide a means to understand the model predictions of the impact foot shape.

In this study, we present an exact derivation of a meso-scale mathematical model for analyzing heat transfer in nanofluids through variational convergence, targeting the reduction of discrepancies between theoretical predictions and experimental data. The model derives distinct sets of partial differential equations for microscale, mesoscale, and macroscale simulations, taking into account several influencing factors across different scales. By employing the weak convergence of distributions and the theory of distributions, we establish variational convergence between the PDEs at different scales. Significantly, the mesoscale model leads to a derivation of the quadratic dependence of thermal conductivity on the particle volume fraction. Our numerical evaluations reveal a marked improvement in prediction accuracy, with the proposed model reducing prediction error in some cases by as much as 92% compared to some existing linear models. Additionally, when tested against available experimental data, the model shows a closer alignment reinforcing its potential for enhancing the prediction and understanding of nanofluid heat transfer. Hence, this paper represents a valuable contribution to nanofluid heat transfer research, providing a promising direction for future advancements in the field. [ABSTRACT FROM AUTHOR]

Externally bonded fiber-reinforced polymer (EB-FRP) laminates have become popular for strengthening existing reinforced concrete (RC) structures. However, the high tensile strength of the FRP laminate is often not fully utilized due to premature debonding failure of the FRP-to-concrete interface, typically occurring in a thin layer beneath the bond interface. Numerical simulations have gained significant attention as a supplement to experimental tests, as they have the ability to provide valuable insights into the debonding process. However, most existing numerical models for EB-FRP joint debonding are unable to explicitly consider cracks within different concrete phases [i.e., mortar and interfacial transition (ITZ)], or precisely capture the corresponding failure mechanisms involving mortar cracking, ITZ debonding, and kinking. This study proposes a novel mesoscale phase field model for concrete, which is capable of accurately modeling complex failure behaviors, including mixed-mode fracture in both the mortar and ITZ, as well as friction on cracked surfaces. The ITZ is regularized using an auxiliary interface phase field and then the overall mixed-mode failure behaviors in both the mortar and ITZ are modeled using a unified damage phase field. To validate the proposed mesoscale model, three pull-off tests of FRP-to-concrete bonded joints, which have been well reported in the existing literature, are simulated. Moreover, the model is used to investigate the effects of adhesion and the FRP laminate on the debonding behavior of the FRP-to-concrete joints. [ABSTRACT FROM AUTHOR]

Microcapsule-based self-healing cementitious composite (MSCC) offers autonomous damage repair, extending the service life of structures. However, most of the existing studies focus on static behavior and healing effectiveness but rarely explore dynamic responses. This study developed the mesoscale modeling approach to investigate MSCC behavior under dynamic split tensile loading. At the mesoscale, MSCC can be treated as a four-phase composite consisting of coarse aggregates, interfacial transition zones, cement mortar, and microcapsules. Alternatively, it can be simplified as a two-phase composite comprising a homogeneous mortar matrix and microcapsules. Four-phase and two-phase mesoscale MSCC models were developed for 2D simulations, while a two-phase 3D model was also developed for comparison. Mesoscale numerical simulations were conducted based on Split-Hopkinson Pressure Bar Brazilian disk-splitting tests, considering various strain rates. Simulation results of different mesoscale models were compared with experimental results. All of the models accurately predicted the tensile strength of MSCC, with the 2D four-phase model providing the best representation of failure modes and crack propagation. Both experimental and numerical data exhibited obvious strain rate effects, indicating that MSCC’s mechanical properties were sensitive to the loading rate. Dynamic increase factors were obtained, quantifying rate sensitivity. The obtained dynamic mechanical properties of MSCC provide insights for designing MSCC components and structures that can better withstand collisions or explosions.

Microstructural features such as voids, microcracks and interfaces play an important role in the mechanical properties of polymer‐bonded explosives, which significantly decide the performance, safety and reliability. A series of micron‐scale 3D models were constructed, and a 3D cohesive finite element method in a commercial software was used to study the elastic properties and fracture development of HMX/Estane polymer‐bonded explosives under quasi‐static tension. The predicted Young's modulus of HMX/Estane PBX with particle volume fraction of 92.7 % at 0.01 s−1 is 2.24 GPa, which is only 7.4 % different from the experimental result. 3D models perform better than 2D models in the prediction of Young's modulus and Poisson's ratio, and the difference between 2D and 3D results can be up to 40 %. In addition, the effect of particle size on the mechanical properties is investigated. It is shown that 3D models can correctly describe the relationship of particle size with stress‐strain curves and fracture development of PBX. Results demonstrate that a 3D model is necessary in the study to delineate the relationships between microstructural features and the mechanical behavior of polymer‐bonded explosives. [ABSTRACT FROM AUTHOR]

The meso-structure of woven fabrics plays a pivotal role in enabling significant deformations. To precisely characterize the deformation behavior of woven fabrics, a mesoscale model based on their meso-structure is developed. In this model, the fiber yarn is represented as a Timoshenko beam with fluctuations described by the shape function. A novel approach is proposed to establish the relationship between the macroscopic mechanical response and the infinitesimal strain of the beam, employing the principle of virtual work. The shearing behavior of woven fabrics is characterized by considering friction energy dissipation and transverse compression among fiber yarns. The general applicability of the proposed model is validated through its application to glass fiber woven fabrics and jute fiber woven fabrics. The model parameters are determined through uniaxial tensile and bias-extension experiments. The accuracy of the model is verified using bias-extension and picture frame experiments. The results demonstrate that the proposed model can effectively simulate the large deformation of woven fabrics. [ABSTRACT FROM AUTHOR]

The alkali–silica reaction (ASR), a major cause of cracks in concrete, is a critical issue in the maintenance of social infrastructure. In this study, a concrete mesoscale model was meticulously developed, and a coupled stress–moisture model was also developed to reproduce ASR degradation. The aim was to investigate the effect of ASR degradation on the bending load-carrying capacity of RC beams. The concrete mesoscale model, specifically designed to reproduce ASR degradation, was modeled from three phases: coarse aggregate, mortar, and ITZ (interfacial transition zone). ASR was considered as the expansion of the coarse aggregate, and the objective was to reproduce expansion cracks with numerical analysis using the mesoscale model. Uniaxial compression tests were carried out on cylindrical specimens with ASR-accelerated deterioration to clarify the relationship between ASR deterioration and compressive properties, and the experimental results were used to identify material parameters in the mesoscale analysis model. The results showed that the model proposed in this study can reproduce the change in compressive properties due to expansion cracking. Finally, RC beams were constructed using the mesoscale model, and the effect of ASR degradation on the bending load-carrying capacity of the RC beams was investigated. The results showed that the presence of expansion cracks caused the initial stiffness of the load-displacement curves to decrease, but the bearing capacity tended to increase. This suggests that factors other than cracks, such as chemical prestress and boundary conditions in this model, have a strong influence on the load-bearing capacity of deteriorated RC beams.

Transcription factors (TF) bind to chromatin and regulate the expression of genes. The pair Myc:Max binds to E-box regulatory DNA elements throughout the genome to control the transcription of a large group of specific genes. We introduce an implicit modeling protocol for Myc:Max binding to mesoscale chromatin fibers at nucleosome resolution to determine TF effect on chromatin architecture and shed light into its mechanism of gene regulation. We first bind Myc:Max to different chromatin locations and show how it can direct fiber folding and formation of microdomains, and how this depends on the linker DNA length. Second, by simulating increasing concentrations of Myc:Max binding to fibers that differ in the DNA linker length, linker histone density, and acetylation levels, we assess the interplay between Myc:Max and other chromatin internal parameters. Third, we study the mechanism of gene silencing by Myc:Max binding to the Eed gene loci. Overall, our results show how chromatin architecture can be regulated by TF binding. The position of TF binding dictates the formation of microdomains that appear visible only at the ensemble level. At the same time, the level of linker histone and tail acetylation, or different linker DNA lengths, regulates the concentration-dependent effect of TF binding. Furthermore, we show how TF binding can repress gene expression by increasing fiber folding motifs that help compact and occlude the promoter region. Importantly, this effect can be reversed by increasing linker histone density. Overall, these results shed light on the epigenetic control of the genome dictated by TF binding.

There is a constant need to predict the dynamic properties of composite materials already at the design stage. A particularly attractive tool for achieving this goal is mesoscale finite element modeling. This paper presents the mesoscale modeling of the dynamic properties of polymer concrete. The method is based on finite element modeling and substructural identification. Substructural identification is a model updating technique based on frequency response functions. It enables the identification of model dynamic properties considering damping. The presented method is used to model the dynamic properties of a polymer concrete beam. In the first step, the mesoscale finite element model is built and then it is decoupled into substructures: a polymer matrix, aggregates, and an interfacial transition zone (ITZ). Next, the dynamic properties of the polymer matrix substructure are updated, and the model is reassembled. Then, second-stage updating takes place, which consists of determining the parameters of the aggregates and the ITZ. The use of substructural identification made it possible to determine the parameters of substructures that do not exist in an independent, isolated form like the ITZ. Moreover, it allows for determining the amount of damping that ITZ brings to the structure. [ABSTRACT FROM AUTHOR]

High strength concrete (HSC) with superior strength advantage has been gaining widespread attention and engineering endorsement in recent years. For a better understanding of the mechanical responses and failure mechanisms of HSC, a novel three‐dimensional (3D) mesoscale model considering the meso‐structural features of concrete was proposed in this paper. First, a series of uniaxial compressive tests were conducted to investigate the compressive properties of HSC specimens with a strength of 80–90 MPa. After that, a 3D three‐phase mesoscale model consisting of mortar, coarse aggregate, and the interfacial transitional zone (ITZ) between them, was developed to perform the mesoscopic simulations of HSC. Then, systematic analysis and discussions on the compressive properties of HSC were presented in terms of the stress–strain curves, compressive strengths/toughness, failure patterns, cracking process, etc. Results indicate that HSC exhibited obvious brittle failure characteristics, and its strength was significantly related to the water‐to‐cement ratio and mineral admixture. At meso‐level, the cracking behaviors of mortar and ITZ phases were well modeled using the developed mesoscale model. Additionally, it was found that the cracking behavior of HSC was significantly associated with the ITZ characteristics. The developed mesoscale modeling approach has been proven to simulate and investigate concrete's compressive properties in a reliable manner, and can be applied further to the property analysis of concrete materials and structures. [ABSTRACT FROM AUTHOR]

Evidence has been provided that land‐cover changes such as deforestation can have an impact on cloudiness and precipitation. However, conflicting results have been obtained at different scales and places, highlighting our poor understanding of the physical processes involved. Here we focus on mesoscale summer cloudiness in a temperate region, as influenced by a large forest massif (the Landes forest in France). Our study is based on an up‐to‐date atmosphere‐surface mesoscale model (Meso‐NH coupled with SURFEX). Based on observational data, we first optimize the model configuration for our purpose, and show that with a 500 m horizontal resolution we can successfully simulate the higher summer cloud cover observed over the forest, compared to its surroundings. Second, we investigate the physical processes leading to cloud formation in a representative case study. Based on a comparative analysis of diagnostics and budgets over forest and non‐forest areas, we find that the larger sensible heat flux over the forest and its higher roughness are the main drivers of cloudiness, enhancing vertical velocity and boundary‐layer mixing. Third, we simulate the impact of the 2009 Klaus storm that led to the loss of about one third of the trees. Considering 15 representative convective summer days, we show that the model simulates well the resulting decrease in summer cloudiness that was reported in a previous study based on satellite observations. As a complementary tool, the mesoscale simulations allow to quantify the impacts of the Klaus storm windthrow on the diurnal cycle of the boundary layer. Plain Language Summary: Previous studies have shown that land‐cover changes such as deforestation can have an impact on cloud cover and precipitation. But the results can be contradictory depending on the region of the world studied. Here, we focus on the temperate Landes forest in southwest France, during the summer period with boundary‐layer clouds. The surface and the atmosphere are represented by two coupled models operating at a 500 m horizontal resolution. We show that, when properly configured, the system can represent boundary‐layer clouds forming over the forest. We then investigate the link between the forest and the generated clouds, highlighting the prominent role of the larger sensible heat flux and roughness over forested areas. These key factors generate vertical motions and mixing that enable cloud formation. Finally, the damage caused by Klaus storm, which destroyed a third of the Landes forest in 2009, is considered. Fifteen summer days with clouds over the Landes are simulated and show that the damage leads to a decrease in cloudiness, in agreement with the results of a previous study based on satellite image analysis. At the regional scale, recent models can thus be used to study and quantify the impact of deforestation on cloudiness. Key Points: A mesoscale model successfully simulates cloud enhancement by a temperate forest and provides realistic cloud fields at hectometric resolutionA comparison of the physical processes over forested and non‐forested areas shows that sensible heat flux and surface roughness are the key drivers of cloudinessThe model helps to understand and quantify the substantial decrease in forest‐induced cloudiness that was observed after storm Klaus [ABSTRACT FROM AUTHOR]

This article discusses the expected climate changes in Belarus as a result of two types of land transformation—rewetting degraded peatlands and increasing forest cover. The analysis was performed for the growing season (May–September) based on long-term earth remote sensing data, mesoscale modeling of atmospheric processes, and balance calculations using ERA5 reanalysis. It is shown that, as a result of waterlogging, the daytime temperature of the land surface for the southern part of Belarus (below the latitude of Minsk) decreases within 1.5°С due to increased evaporation and, for the northern part, 0.5 increased due to albedo regularity. At night, waterlogging, depending on the soil and climatic conditions, can cause both an increase and decrease a specific value of the land surface temperature (LST) within 1°C. Evapotranspiration due to waterlogging in the northern regions of Belarus decreases and it increases in the southern regions, which is associated with a significant ratio between evaporation and transpiration in these regions. During the afforestation of cropland, the daytime LST of Belarus decreases within 2°C and, at night, increase. The total evapotranspiration for the growing season due to the increase in forest cover reaches 100 mm, and potential (maximum possible) evaporation remains at the same level, which contributes to an increase in soil moisture at an increased amount of atmospheric precipitation. The above changes in the physical characteristics of the land surface as a result of reclamation cause a decrease in the surface air temperature in the reclamated region within 0.4°C and an increase in the amount of atmospheric precipitation within 2% of the climatic normals. At the same time, the maximum in the spatial distribution of secondary precipitation due to western transport shifts to the east relative to the reclaimed region. [ABSTRACT FROM AUTHOR]

Polyolefins account for more than half of global primary polymer production, however only a small fraction of these polymers are currently being recycled. Fragmentation of polymer chains into shorter chains with a targeted molecular weight distribution with the goal of reusing these fragments in subsequent chemical synthesis can potentially introduce an alternative approach to polyolefins recycling. Herein we develop a mesoscale framework to model degradation of polyethylene melts at a range of high temperatures. We use the dissipative particle dynamics approach with modified segmental repulsive potential to model the process of random scission in melts of linear polymer chains. We characterize the fragmentation process by tracking the time evolution of the distribution of degrees of polymerization of chain fragments. Specifically, we track the weight average and the number average degrees of polymerization and dispersity of polymer fragments as a function of the fraction of bonds broken. Furthermore, we track the number fraction distribution and the weight fraction distribution of polymer fragments with various degrees of polymerization as functions of the fraction of bonds broken for a range of high temperatures. Our results allow one to quantify to what extent the distribution of polymer chain fragments during random scission can be captured by the respective analytical distributions for the range of conversions considered. Understanding the thermal degradation of polyolefins on the mesoscale can result in the development of alternative strategies for recycling a range of thermoplastics.

The seismic performances of 28 geometrically similar concrete shear walls reinforced with basalt fiber-reinforced polymer (BFRP) bars were simulated using a mesoscale modeling approach. In the modeling, concrete heterogeneities were explicitly described, and the interaction between BFRP bars and surrounding concretes was also considered. The influences of shear depth, shear span ratio and vertical reinforcement ratio on the failure of shear walls were investigated. The simulation results indicated that with the increase of shear depth, the failure modes were basically the similar, while the nominal shear strength decreased significantly, namely, the presence of size effect was demonstrated. The shear wall would exhibit different failure modes as the shear span ratio varies. Moreover, it was found that the vertical BFRP bar presented an ignorable influence on the failure mode, while the increase of vertical reinforcement ratio would obviously improve the shear strength of BFRP-RC shear wall. Finally, the present simulated shear strengths were compared with some available size effect laws and some codes. [ABSTRACT FROM AUTHOR]

The yarn weave architectures highly influence the mechanical response of woven fabrics. To provide an accurate prediction of the mechanical behaviors of woven fabrics under tension, a mesoscale model is developed. The model takes into account yarn properties, yarn weaving pattern, and interactions between yarns. The yarn properties such as tensile modulus and yarn strength of yarns are considered as random variables. Each yarn in fabric is modeled as a Timoshenko beam with a weaving shape modeled by a parabolic function. The yarn shape evolution and mechanical response of undulated yarn under tension are computed based on Castigliano's second theorem. The damage initiation and propagation of a yarn in fabric is introduced through a damage variable. The model is demonstrated on woven jute fabrics. Analytical and numerical analyses are carried out and show good prediction on the macroscopic tensile response of woven jute fabric. The model provides a quantitative understanding between yarn geometrical parameters and the expected material response, and makes it helpful for designing woven structural composites with high performance. [ABSTRACT FROM AUTHOR]

Density Functional Theory (DFT) calculations can determine planar defect energies and slip pathways that are present in ordered intermetallic systems used to strengthen Ni-based superalloys, but analytical models used to evaluate the strengthening effects of these phases often involve significant simplifying assumptions. Instead, Phase Field Dislocation Dynamics (PFDD) is a useful modeling tool that incorporates dislocation interactions with precipitates and slip pathways informed by DFT to determine how precipitate shearing might occur under applied stresses with improved accuracy over previous models. In this work, we apply PFDD to study precipitate shearing in HAYNES® 244®, a high strength Ni-based superalloy strengthened through a novel Ni 2 (Cr, Mo, W) phase that has a low symmetry Body Centered Orthorhombic (BCO) crystal structure which complicates analysis of slip pathways. Through our modeling, we show the formation of and evolution of extended dislocations in the matrix and in the precipitates, the interaction of dislocations with the precipitates, and the formation of planar faults in the precipitate. A key aspect of incorporating the DFT determined slip pathway is the influence of the unstable fault energy and the asymmetry of the energy pathway on the strengthening aspect of the precipitate. The resulting critical strengths are compared to analytical models. The size, orientation, particle distance, and calculated slip pathway for the different variants in this system are all shown to have an important effect on the critical stress to shear these precipitates. [Display omitted] [ABSTRACT FROM AUTHOR]

The aggregate skeleton and its evolution under external loads are crucial to evaluate the mechanical properties of the asphalt mixture. This study developed a method to identify the three-dimensionally (3D) aggregate skeleton based on geometry information. The proposed method can identify the evolution process of the aggregate skeleton during loading in the finite element method (FEM). Random models based on the Gilbert–Johnson–Keerthi (GJK) algorithm are used to study the influence of the concave–convex degree of the gradation curve and the magnitude of the creep load on the aggregate skeleton during the creep process. The results indicate that the aggregate skeleton undergoes three stages during creep: aggregate redistribution, skeleton formation, and skeleton failure after reaching the ultimate load, while the increase of load causes the aggregate skeleton to lose its bearing capacity faster. More coarse aggregate raises the strength of the aggregate skeleton, but it is more likely to break down quickly once it reaches the strength. More fine aggregate enhances the stability of the aggregate skeleton. The proposed identification method can serve as a general tool to investigate the evolution process of the internal aggregate structure of the asphalt mixture. [ABSTRACT FROM AUTHOR]

In this paper, a dual-scale modeling approach is established to predict polymer-CNT composites' elastic and thermal properties. The standard computational platform, i.e., DIGIMAT, was used to execute the mesoscale modeling. A 3D random representative volume element model in conjunction with the mean-field homogenization method is developed for the mesoscale computational analysis. With the assumption of perfect bonding, mesoscale modeling reveals the composites' orthotropic elastic and thermal nature. Periodic boundary conditions were imposed to obtain the orthotropic nature at the mesoscale. The fracture toughness (mode-I stress intensity factor, KI) of the composites was studied at a macroscale using the mesoscale modeling's orthotropic properties. The computational Young's modulus and fracture toughness were found in good agreement with the experimental results. The experimental Young's modulus of HDPE and LDPE composites has shown a variation from 7.26 ± 1.81 to 3.86 ± 1.44, and 3.81 ± 0.57 to 0.92 ± 0.32 GPa, respectively, with an increase in environmental temperature from 25 to 100 °C. The experimental fracture toughness has varied from 1.81 ± 0.09 to 0.26 ± 0.03, and 1.49 ± 0.12 to 0.07 ± 0.01 MPa-m1/2, respectively, for HDPE and LDPE composites, with an increase in environmental temperature from 25 to 100 °C. A statistical analysis (Weibull distribution) has also been performed to investigate the considered composites' strength. The study reveals that the temperature has a noticeable effect on the softening, reducing the composites' strength. Fractographic analysis on the tested composites using scanning electron microscopy reveals the composites' failure due to the debonding of CNTs, softening of the matrix, formation of holes, and rough patches. The obtained numerical results can provide a suitable reference to study the fracture problems in other polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Recent observational and numerical studies have investigated the dynamics of fine‐scale gravity waves radiating horizontally outward from tropical cyclones. The waves are wrapped into spirals by the tangential wind of the cyclone and are described as spiral gravity waves. This study addresses how well numerical simulations of these waves compare to observations as the horizontal grid spacing is decreased from 2.0 to 1.0 to 0.5 km, and the number of vertical levels changes from 25 to 50 to 100. Spectral filtering is applied to separate the fine‐scale waves in vertical velocity (w) and the larger‐scale waves in pressure (p) from moist updrafts and downdrafts in the eyewall and rainbands. As the grid spacing decreases, the radial wavelengths of the w waves decrease from 20 to 7 km, approaching observed values. For grid spacing 1.0 km, the p waves become well‐resolved with wavelength 70 km. The outward phase speeds range from 15 to 30 ms−1 for the w waves and 50 to 70 ms−1 for p waves. Analysis of the upper‐level outflow region finds that the spiral w waves propagate 5–10 ms−1 faster due to radial advection, but also finds what appear to be different classes of larger‐amplitude, slow‐moving spiral waves. Similar waves can be seen in satellite images, which appear to be caused by dynamical instability of the strongly vertically sheared radial and tangential winds in the TC outflow. Plain Language Summary: Tropical cyclones—known also as hurricanes, typhoons, and cyclones—cause some of the most significant weather impacts around the world. Recent work has found that these storms causes oscillations in the atmosphere that radiate outward in expanding spirals. These are called spiral gravity waves. This paper investigates how well computer models reproduce these waves as the pixel sizes used by the model become smaller (requiring more computer power). As the pixels decrease to 1.0 km or less, the waves become increasingly realistic. The simulations show two types of spiral gravity waves, which can be seen either in vertical motion or in the atmospheric pressure field. The vertical motion waves are 5–10 km wide and move outward at 90 km hr−1, while the pressure waves are 60–80 km wide and move outward at 220 km hr−1. Focusing on the cloud shield at the top of the cyclone (what we see in satellites) reveals a new class of slow‐moving, spiral waves that are distinct from the gravity waves. Key Points: Computer simulations of tropical cyclones show the detailed structures of outward propagating spiral gravity wavesAs resolution increases, the wave properties come close to, but do not converge to observed valuesA new class of waves is identified in the upper‐level outflow, which are slow‐moving spiral waves due to dynamical instabilities [ABSTRACT FROM AUTHOR]

Understanding Fuel Fragmentation, Relocation and Dispersal (FFRD) phenomena is a major item to predict the behavior of fuel rods in the event of a Pressurized Water Reactor loss-of-coolant hypothetical scenario. In order to introduce an effective medium for fragmented fuel that could be used in fuel performance codes, the heat transfer properties of U O 2 granular beds in He-Kr-Xe gas mixes was studied numerically. The Discrete Element Method was first used to compute the spatial arrangement of fragments only submitted to gravity with a representative granulometric distribution. These generated geometries were then transformed into a 3D grid (voxelized) to perform numerical homogenization and compute their effective properties using a Fast Fourier Transform solver for heat transfer. Different hypotheses were made in the voxelation process about the treatment of gas-solid and solid-solid interfaces, which in turn provided different estimates of the effective properties. Due to limits on the discretization and extended particle size distributions, a two-scale scheme was introduced and numerically tested against direct computations. For several granular beds, computed thermal conductivities were compared to analytical models for granular materials. Some heat transfer properties of fragmented fuel at several burnups were then computed, taking into account approximations for Knudsen and radiation size effects. [ABSTRACT FROM AUTHOR]

• Introduced a novel granular model for analysing rockburst mechanisms. • Validated the true triaxial rockburst model with experimental correlations. • Identified reduction in rockburst strength due to anisotropy angle variations. • Documented diverse micro-crack evolution associated with anisotropic changes. Rockbursts pose significant concerns in underground construction, and understanding their mechanisms is crucial for enhancing safety in tunneling and underground mining operations. This study innovates an inherently anisotropic rock model using the discrete element method to investigate the effect of local strength degradation on rockburst behavior. Unlike the existing rockburst models in which the anisotropy is either not accounted for or simulated by creating transversely weak planes, the inherent anisotropy is achieved in the contacts between rock grains. Following model calibration, the accuracy of the proposed model is demonstrated by simulating the behavior of rock samples subjected to triaxial rockburst tests. The findings highlight the influence of loading conditions on rockburst behavior in inherently anisotropic rocks and compare micro-crack patterns after rockbursts under different triaxial loading stresses and mesoscale failure types. Notably, this study is the first attempt to combine an inherently anisotropic rock model with rockburst analysis, providing new insights into the mesoscale mechanisms underlying rockburst failure. Notably, it reveals a significant variation in rockburst strength, by about a third, when the anisotropy angle shifts from 0 to 90 degrees. The proposed inherently anisotropic rock model offers an alternative for evaluating the impact of grain-scale strength degradation on rockburst behavior. [ABSTRACT FROM AUTHOR]

The progressive collapse of reinforced concrete (RC) beam-column sub-assemblage under catenary action (CA) using the alternate load path method to evaluate structures' robustness has raised much attention in the past decade, both in experimental tests and finite element (FE) simulations. However, a comprehensive multiscale method within concrete to assess structural robustness against progressive collapse, explicitly surrounding concrete matrix under CA, is generally lacking and has not been thoroughly explored in the relevant literature. This study aims to develop an FE macromodel to reliably simulate the progressive collapse resistance of seismic and non-seismic RC beam-column sub-assemblages. The proposed macroscale FE models are extensively validated by experimental results dominated by the CA and excessive deformation of RC beam-column sub-assemblages. Then, the macroscale FE model is further partitioned at the critical region with high-stress concentration to establish a sub-model and elucidate the underlying mesoscopic mechanism to motivate the CA by performing sub-modeling analysis. A 150 mm × 150 mm × 150 mm mesoscale heterogeneous model is established to be composed of aggregates, interfacial transition zone (ITZ), pores, and mortar by 3D voxel and Voronoi-based methods. The numerical predictions of the three macroscale models demonstrate good agreement of the overall deformation and load resistance trends with experimental results at both structural and sectional levels, but an overestimation of the load resistance peak is observed when concrete is crushed. Compared to the macroscale models, the sub-modeling analysis provides a more in-depth understanding of localized phenomena such as cracks and fractures. The 3D mesoscale model is further investigated with different aggregate volume fractions following the Fuller gradation. It is found that aggregates and ITZ (higher porosity, lower elastic modulus, and lower tensile strength compared to the bulk mortar) are more prone to concrete failure mechanisms without considering the role of reinforcement leading to the CA at the mesoscale, maintaining the concrete properties of the three macroscale models. In terms of the material constitutive model, the concrete damage plasticity model, and cohesive elements for mortar and ITZ, respectively, under uniaxial compression and tension behavior, the importance of interface bonding in CA of the surrounding concrete matrix is underlined. Additionally, the established mesoscale modeling method facilitates comprehension of the responses exhibited by macroscale RC sub-assemblies, ultimately shedding light on fracture initiation and propagation mechanisms. • Numerically predict a macroscopic model resistance under catenary action. • Further improve accuracy and dependability of resistance capacity in submodelling. • Unveil the resistance contributions in mesoscale modeling under progressive collapse. [ABSTRACT FROM AUTHOR]

We use a combination of a regional climate model (RCM) and a global climate model (GCM) to explore potential changes to the complex precipitation regime in the semi‐arid and arid state of Arizona in the American Southwest. The RCM output for the contemporary period (2000–2009) compares well with a gridded precipitation dataset with respect to seasonality, amount, intensity, and diurnal patterns. Output from the GCM forced by the continued buildup of greenhouse gases was dynamically downscaled by the RCM for the period 2090–2099. Results indicate an increase in winter precipitation of 1–2 mm day−1 in the mountainous areas of the state with somewhat smaller increases for the summer and fall seasons; negligible changes were projected for spring precipitation. Extreme precipitation is projected to increase across much of the state in winter (10–30 mm day−1) and to a lesser extent in spring. Our results indicate an increase in the 99th percentile of winter season precipitation. However, we note there is substantial seasonal dependency: statewide‐averaged winter season precipitation is projected to undergo greater frequency of wet than dry extreme events, whereas the statewide‐averaged summer, fall, and spring seasons, broadly demonstrate an equal likelihood of increased and decreased extreme precipitation. While the RCM captured the unusual observed night‐time maximum in summer rainfall in the centre of the state, our results do not indicate any change in the diurnal character or sub‐diurnal duration (6–18 hr) of precipitation over the next 100 years. [ABSTRACT FROM AUTHOR]

A polymer nanocomposite based on a symmetrical AB diblock copolymer filled with planar nanoparticles (NPs) has been studied by the dissipative particle dynamics method. The developed model predicts that NPs can reduce the threshold of thermodynamic incompatibility of blocks A and B, above which microphase separation of the polymer matrix occurs to give a lamellar phase. Depending on the features of the polymer/NP interaction, two types of stable orientations of the NP plane are formed: along and across the lamellar domains. This effect can be used to control the distribution of NPs in multiphase polymeric materials. [ABSTRACT FROM AUTHOR]

This work aims to implement an efficient and accurate computational model to predict elastoplastic properties of UHMWPE/nano-HA bio-composite. Mean-field (MF) homogenization and finite element (FE) techniques are implemented to predict the elastoplastic behavior of composite. The predicted results obtained by MF and FE were compared and validated experimentally by fabricating the specimen using microwave-assisted compression molding. The axial and transverse moduli were increased by 49% at a 20% weight fraction of nano-HA. The hardening modulus was also found to be increased by 67%. Further, Degree of crystallinity (Xc) of fabricated composite specimens was determined using differential scanning calorimetry analysis. It was found that the Xc increased 34% with the addition of 20% weight fraction of nano-HA. In vitro, direct contact cytotoxicity and antibacterial test were performed to determine cell adhesion and bacterial behavior of the composite. [ABSTRACT FROM AUTHOR]

This study investigates the impact of aggregate and pipe cooling systems on concrete behaviour at a mesoscale level. Firstly, a Chemo- Thermo-Mechanical model is developed to investigate the initial stress state of early age hydration concrete followed by a mechanical analysis of the consequences brought by this initial state. Pipe and aggregate cooled concrete samples have been subjected to tensile and cyclic loadings. The results have been discussed in terms of damage and crack openings. It has been concluded that early age hydration modifies the initial conditions of any concrete structures. Regarding the cyclic behaviour, initial state due to the hydration process leads to permanent displacements corresponding to damage and cracking. The cooling methods improve the mechanical behaviour of concrete. [ABSTRACT FROM AUTHOR]

As a subsequent paper for "type-A-choking-oriented unified model for fast fluidization dynamics", the present work aims to provide more systematic mesoscale analyses on clusters. Starting from theoretical derivations on idealized flow patterns of gas and solids around a single falling cluster; the momentum consumption due to particle circulation in clouds and the modification of flows by the constraint of driving force available in the bed were addressed. Complete compensation of the pressure-drop driven percolated gas in clusters by the reversely-penetrating particles was used for the ultimate closure of the model. An important finding of the present work, different from most empirical correlations, but verified by Wei and Zhu's latest experimental data and others, is that the cluster diameter does not vary monotonically with the mean solids holdup of the bed, but has a maximum value in between. Demonstrative calculations show that it is easy for Group A particles to enter the flow regime of high-density fast-fluidization as the circulating solids flux increases continuously, while fast fluidization for Group B particles tends to be stopped at Type C choking in advance. Compared with Group A particles, the clusters for Group B particles are less dense, but the penetration velocities of particles are higher, resulting in much larger dimensionless diameters of clusters. Finally, issues of pseudo-2D fast-bed modeling were discussed, and modeling of fast-beds with uneven flow fields was outlook briefly. [Display omitted] • Idealized flow patterns of gas and solids around single falling cluster were obtained. • Modifications of flow/pressure fields due to particle circulation in cloud were made. • Percolated gas in cluster offset with inversely penetrating particles to close model. • Cluster diameter don't vary monotonically with solids holdup but has maximum in range. • Main differences of fast fluidization of Group-A and Group-B particles were predicted. [ABSTRACT FROM AUTHOR]

Tropical cyclogenesis and rapid weakening are subjects of considerable interest in the literature. This paper addresses the genesis and rapid weakening of a North Indian Ocean tropical cyclone Lehar (November 23–28, 2013). High-resolution analysis has been created by assimilating GPSRO observations using WRF and 3DVAR assimilation techniques. The parent disturbance of tropical cyclone Lehar is traced back using a moisture variable, and it is found to be originating from a westward-moving disturbance. The pathway of genesis is found to be bottom-up, with the vorticity developing from below. Tropical cyclone Lehar weakened from a Category 1 cyclone on November 26, 2013. We analyzed the prospects that contributed to the abrupt drop of tropical cyclone Lehar's intensity in view of this. The analysis shows dust in the post-genesis (rapid weakening) environment of tropical cyclone Lehar. The analysis of total precipitable water in the post-genesis environment shows that the environment is very dry (< 45 kgm−2), and the spiral bands started disappearing under the influence of dry air intrusion. It has been found that the tropical cyclone Lehar is interacting with the dry air coming from the northern part of the Indian region during the post-genesis (rapid weakening) evolution, and the cyclone started weakening rapidly. The dry air advection from the north of the storm is a primary contributor to the weakening and high deep layer shear in the weakening environment. [ABSTRACT FROM AUTHOR]