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In this paper, a homogenized multiphase lattice Boltzmann (LB) model is established for parallelly simulating immiscible two-phase flow in both solid-free regions (pore scale) and porous areas (continuum scale). It combines the color-gradient multiphase model with the Darcy–Brinkman–Stokes method by adding a term that includes surface force and drag force of porous matrix to multiple-relaxation-time LB equation in moment space. Moreover, an improved algorithm is proposed to characterize and implement the apparent wettability in the locally homogenized porosity field. Validations and test cases are given to demonstrate the accuracy and robustness of this new model, as well as its applicability for trans-scale fluid simulation of transport and sorption behavior from porous (Darcy flow) area to free (Stokes flow) area. For practicality, the two-phase seepage flow in a composite rock structure with multiscale pores is simulated by this new model, and the effects of viscosity ratio and wettability on the displacement process are discussed. [ABSTRACT FROM AUTHOR]

The Lattice Boltzmann Method (LBM) is an approach for modeling mesoscopic fluid flow and heat transfer, based on modeling distributions of particles moving and colliding on a lattice. Using a perturbative formulation of the Boltzmann equation, it scales to the macroscopic Navier–Stokes equation. We simulate natural thermal convection via LBM in a 2D rectangular box being heated from below and cooled from above, and use the results as training, testing, and generalization datasets to build a deep learning model. GoogLeNet, a convolutional neural network, is used to classify the simulation results based on two parameters: Rayleigh (R a) and Prandtl (P r) numbers, from a single snapshot of either the entire modeling field of resolution 1024 × 1024 , or a 224 × 224 crop. For each fixed P r in a range from 1 to 128, increasing by a factor of 2, we estimate R a with an accuracy varying from 40% to 90%, depending on the chosen augmentation strategy. For each fixed R a in the range from 10 5 to 10 9 , increasing of a factor 10 , the method predicts P r with a systematically lower accuracy ranging from 30% to 80%. This approach has great potential for industrial applications like being able to control the industrial flow or scientific research on geophysical ones including the transport of heat in the earth's interiors, ocean, and atmosphere. [ABSTRACT FROM AUTHOR]

For multi-layered 2D materials, although its c-axis has a much lower thermal conductivity than the a-axis, its phonon mean free path has been confirmed to be very long, e.g., in the order of 100s nm at room temperature for multi-layered graphene. An anisotropic specific heat concept has been proposed in the past to explain this very long mean free path. This work carries out detailed atomistic modeling to quantify the anisotropic specific heat concept and reports the discovery of anisotropic temperatures in multi-layered 2D materials under ultrafast surface heating. Extremely fast c-phonon energy transport is discovered, and the non-Fourier effect is observed for both a-phonons and c-phonons. The energy coupling factor between these two modes of phonons is determined to be in the order of 1016 W K−1 m−3, with the specific number depending on the structure location. The anisotropic temperature concept is also quantitatively confirmed based on the lattice Boltzmann method simulation. The anisotropic temperature concept does not violate the physics that temperature is a scalar; rather, it is developed to distinguish the temperatures of phonons that travel in different directions. This concept is universally applicable to other 2D materials to describe the heat conduction in the in-plane and out-of-plane directions that feature different interatomic bonds. [ABSTRACT FROM AUTHOR]

This paper is on the motion of a neutrally buoyant but circular slip particle in a clockwise double-lid-driven square cavity. The slip flow at the particle surface is implemented by the lattice Boltzmann method with corrected slip boundary schemes. The effects of slip length (Ls), initial particle position, Reynolds number (Re), and particle size (D) are studied on the migration of the slip particle. The motion of the circular slip particle is dominated by the centrifugal and boundary-repulsion forces. The results show that the cavity center is the unique fixed point, and once the slip particle initially deviates from the cavity center, it is always stabilized at the same limit cycle. With the increase in slip length, the limit cycle of the circular slip particle is closer to the cavity boundaries, which brings a stronger centrifugal force to balance the increased boundary-confinement effect. As the slip length, Ls, exceeds 0.02D, the limit cycle forms more quickly than the circular no-slip particle. When Re increases to within 1000, the limit cycle is squashed along the leading diagonal of the cavity and pushed toward the boundaries; however, when Re increases beyond 1000, two developing secondary vortices confine the limit cycle to shrink toward the cavity center. With the increase in particle size, the enhanced boundary confinements lead to the shrinkage of the limit cycle toward the cavity center. [ABSTRACT FROM AUTHOR]

The phenomenon of water–ice phase transition in frozen soils is the key to explaining the mechanism of frost heaving and thawing settlement disaster. However, numerical analysis of water–ice phase transitions in frozen soils at mesoscale is rarely reported. This study combines the modified Gibbs-Thomson equation and the enthalpy-based lattice Boltzmann model, and develops a mesoscale numerical method to simulate the water–ice phase transition in the local pores of saturated frozen soil during freezing and thawing process. In order to accurately simulate this process, a new η coefficient is proposed to modify the Gibbs-Thomson equation, which is unrelated to the type of soil sample and gradation characteristics. According to the particle size distribution curve, the two-dimensional random circle generation method is used to reconstruct the soil pore structure. The freezing and thawing processes are verified with the experimental data. A larger non-uniformity coefficient Cu and curvature coefficient Cc of the grain size distribution result in a lower degree of subcooling and lower residual water content of the soil during the freezing process. The new model provides an effective means to understand the water–ice phase transition in frozen soil at a mesoscopic scale. [ABSTRACT FROM AUTHOR]

This paper adopted the Lattice Boltzmann Method (LBM) to compute a two‐dimensional incompressible convective flow field with two isothermal elliptical sinks attached vertically to the horizontal bottom north side of the enclosure, which is subjected to a horizontal magnetic field. The attained results show that LBM can effectively capture vortex shedding structures and other features inside such complex flow. Also, the Hartmann numbers with a panoply of heated sinks location were studied, and the results showed that fluid flow and heat transfer rate depend on the Hartmann number and are greatly influenced by the heated sinks positions. The effect of the Prandtl number on the average Nusselt number is also highlighted. [ABSTRACT FROM AUTHOR]

The impetus of this paper is to examine the natural convection of low-Prandtl-number fluid flow driven by buoyancy force in a differentially heated enclosure using the single-relaxation-time thermal lattice Boltzmann method owing to the broad range of applications of convective-based problems in industry, such as melting processes as well as energy storage systems. In this study, a proper force term incorporated in the collision operator has been utilized for computer code convergence (especially for Prandtl numbers less than 0.71). The side walls of the geometry are maintained by constant temperatures, Th and Tc, and the upper and lower walls are thermally insulated. The effects of Prandtl ( 0.05 ≤ Pr ≤ 0.71 ) and Rayleigh numbers ( 10 4 ≤ Ra ≤ 5 × 10 5 ) on the temperature fields, streamline functions, and average Nusselt number have been studied and found that at a given Prandtl number, the magnitude of vortices at the corner of the enclosure rises while those could disappear by Prandtl number increase. In addition, in the vicinity of hot and cold walls, the isotherms concentration increases due to rising temperature gradient and Prandtl number. The heat transfer coefficient grows with an increase in Ra and Pr numbers, experiencing a dramatic rise of 66.67% at the hot wall for Pr = 0.1. Similarly, the maximum velocity values near the cold wall rose by 185.71%. The suggested scheme has been validated by results shown in the literature, and excellent agreement has been found. [ABSTRACT FROM AUTHOR]

For use with the lattice Boltzmann method, the macroscopic boundary conditions need to be transformed into their mesoscopic counterparts. Commonly used mesoscopic boundary conditions use the equilibrium density function, which introduces undesirable artifacts into the numerical solution, especially near interfaces with other types of boundary conditions. In this work, several variants of the mesoscopic boundary conditions are summarized and numerically investigated by means of benchmark problems for the incompressible Navier-Stokes equations with known analytical solutions. To improve the numerical approximation of the velocity and pressure fields, moment-based boundary conditions are extended for the D3Q27 velocity model. Furthermore, the interpolated boundary conditions are improved. These newly developed boundary conditions are shown to produce results with a substantially smaller numerical error. [ABSTRACT FROM AUTHOR]

We have presented a novel lattice Boltzmann approach for the non‐uniform rectangular mesh based on the radial basis function approximation (RBF‐LBM). The non‐uniform rectangular mesh is a good option for local grid refinement, especially for the wall boundaries and flow areas with intensive change of flow quantities. Which allows, the total number of grid cells to be reduced and so the computational cost, therefore improving the computational efficiency. But the grid structure of the non‐uniform rectangular mesh is no longer applicable to the classic lattice Boltzmann method (CLBM), which is based on the famous BGK collision‐streaming evolution. This is why the present study is inspired by the idea of the interpolation‐supplemented LBM (ISLBM) methodology. The ISLBM algorithm is improved in the present manuscript and developed into a novel LBM approach through the radial basis function approximation instead of the Lagrangian interpolation scheme. The new approach is validated for both steady states and unsteady periodic solutions. The comparison between the radial basis function approximation and the Lagrangian interpolation is discussed. It is found that the novel approach has a good performance on computational accuracy and efficiency. Proving that the non‐uniform rectangular mesh allows grid refinement while obtaining precise flow predictions. [ABSTRACT FROM AUTHOR]

Data-driven approaches offer novel opportunities for improving the performance of turbulent flow simulations, which are critical to wide-ranging applications from wind farms and aerodynamic designs to weather and climate forecasting. However, current methods for these simulations often require large amounts of data and computational resources. While data-driven methods have been extensively applied to the continuum Navier-Stokes equations, limited work has been done to integrate these methods with the highly scalable lattice Boltzmann method. Here, we present a physics-informed neural network framework for improving lattice Boltzmann-based simulations of near-wall turbulent flow. Using a small amount of data and integrating physical constraints, our model accurately predicts flow behaviour at a wide range of friction Reynolds numbers up to 1.0 × 106. In contradistinction with other models that use direct numerical simulation datasets, this approach reduces data requirements by three orders of magnitude and allows for sparse grid configurations. Our work broadens the scope of lattice Boltzmann applications, enabling efficient large-scale simulations of turbulent flow in diverse contexts. The authors provide a data-driven near-wall modelling framework for the lattice Boltzmann method using IDDES data. Their model can predict flows with friction Reynolds numbers up to 1,000,000 and effectively handle sparse near-wall grids. [ABSTRACT FROM AUTHOR]

A lattice Boltzmann method is used to explore the effect of surfactants on the unequal volume breakup of a droplet in a T-junction microchannel, and the asymmetry due to fabrication defects in real-life microchannels is modelled as the pressure difference between the two branch outlets ($\Delta {P^\ast }$). We first study the effect of the surfactants on the droplet dynamics at different dimensionless initial droplet lengths ($l_0^\ast $) and capillary numbers (Ca) under symmetric boundary conditions ($\Delta {P^\ast } = 0$). The results indicate that the presence of surfactants promotes droplet deformation and breakup at small and moderate $l_0^\ast $ values, while the surfactant effect is weakened at large $l_0^\ast $ values. When the branch channels are completely blocked by the droplet, a linear relationship is observed between the dimensionless droplet length ($l_d^\ast $) and dimensionless time (${t^\ast }$), and two formulas are proposed for predicting the evolution of $l_d^\ast $ with ${t^\ast }$ for the two systems. We then investigate the effect of the surfactants on the droplet breakup at different values of $\Delta {P^\ast }$ and bulk surfactant concentrations (${\psi _b}$) under asymmetric boundary conditions ($\Delta {P^\ast } \ne 0$). It is observed that, as $\Delta {P^\ast }$ increases, the volume ratio of the generated droplets (${V_1}/{V_2}$) decreases to 0 in both systems, while the rate of decrease is higher in the clean system, i.e. the presence of surfactants could cause a decreased pressure difference between the droplet tips. As ${\psi _b}$ increases, ${V_1}/{V_2}$ first increases rapidly, then remains almost constant and finally decreases slightly. We thus establish a phase diagram that describes the ${V_1}/{V_2}$ variation with $\Delta {P^\ast }$ and ${\psi _b}$. [ABSTRACT FROM AUTHOR]

The free‐surface lattice Boltzmann method uses a volume of fluid approach to simulate immiscible two‐fluid flow problems. It divides the simulation domain into three distinct phases—gas, fluid, and interface—where computation within the gas phase is disregarded. The interface delineates a one‐cell‐thick layer between the first two phases, validated physically for implementation in the HPC C++ multiphysics framework waLBerla but lacking an exhaustive performance analysis. This paper aims to shed light on node‐level performance on different architectures, employing continuous benchmarking, showing and analyzing weak scaling results on a modern HPC cluster, the Fritz supercomputer, and reporting energy consumption for the current implementation. [ABSTRACT FROM AUTHOR]

A 2-D Lattice Boltzmann Method, designed to ensure stability at high Reynolds numbers, is combined with an Actuator Line Model to compute the loads on a two-bladed vertical axis wind turbine. Tests on the kernel size at a high mesh resolution reveal that a size equal to half of the full chord length yields the most accurate results. The aerodynamic load solution is validated against a fully resolved Scale-Adaptive Simulation (SAS) output, demonstrating high correlation, and enabling an assessment of near wake and downstream effects. The model's adaptability to various rotor operating conditions is confirmed through tests at high and low tip-speed ratios. Additionally, a Biot–Savart-based Vortex Model (VM) is employed for further comparison, showing good agreement with the Lattice Boltzmann output. The results indicate that the Highly Stable Lattice Boltzmann Method integrated with the Actuator Line Model enhances the accuracy of flow field resolution and effectively captures complex aerodynamic phenomena, making it a valuable tool for simulating vertical axis wind turbines. [ABSTRACT FROM AUTHOR]

We propose a multiple-relaxation-time lattice Boltzmann method for anisotropic convection-diffusion equation with a divergence-free velocity field. In this approach, the convection term is handled as a source term in the lattice Boltzmann evolution equation; thus, the derivation term that may be induced by the convection term disappears. By using the Chapman-Enskog analysis, the anisotropic convection-diffusion equation is recovered up to second-order accurate in space. In particular, we also present a local scheme for computing the convection term, indicating that the present method retains the main advantages of the lattice Boltzmann method. We then test the proposed model by considering the Gaussian hill problem and an anisotropic convection diffusion equation with constant velocity and diffusion tensor. The results illustrate that our model has acceptable numerical accuracy and can be a good candidate for simulating anisotropic convection-diffusion equation. • A MRT LB model is constructed for anisotropic CDE with divergence-free velocity field. • The convection term is treated as a source term in the LB equation. • No deviation term exists in the corresponding recovered equation. [ABSTRACT FROM AUTHOR]

Understanding the niche interactions between blood and bone through the in vitro co-culture of osteo-competent cells and endothelial cells is a key factor in unraveling therapeutic potentials in bone regeneration. This can be additionally supported by employing numerical simulation techniques to assess local physical factors, such as oxygen concentration, and mechanical stimuli, such as shear stress, that can mediate cellular communication. In this study, we developed a Mesenchymal Stem Cell line (MSC) and a Human Umbilical Vein Endothelial Cell line (HUVEC), which were co-cultured under flow conditions in a three-dimensional, porous, natural pullulan/dextran scaffold that was supplemented with hydroxyapatite crystals that allowed for the spontaneous formation of spheroids. After 2 weeks, their viability was higher under the dynamic conditions (>94%) than the static conditions (<75%), with dead cells central in the spheroids. Mineralization and collagen IV production increased under the dynamic conditions, correlating with osteogenesis and vasculogenesis. The endothelial cells clustered at the spheroidal core by day 7. Proliferation doubled in the dynamic conditions, especially at the scaffold peripheries. Lattice Boltzmann simulations showed negligible wall shear stress in the hydrogel pores but highlighted highly oxygenated zones coinciding with cell proliferation. A strong oxygen gradient likely influenced endothelial migration and cell distribution. Hypoxia was minimal, explaining high viability and spheroid maturation in the dynamic conditions. [ABSTRACT FROM AUTHOR]

Numerical modeling of gas flows in rarefied regimes is crucial in understanding fluid behavior in microscale applications. Rarefied regimes are characterized by a decrease in molecular collisions, and they lead to unusual phenomena such as gas phase separation, which is not acknowledged in hydrodynamic equations. In this work, numerical investigation of miscible gaseous mixtures in the rarefied regime is performed using a modified lattice Boltzmann model. Slip boundary conditions are adapted to arbitrary geometries. A ray-tracing algorithm-based wall function is implemented to model the non-equilibrium effects in the transition flow regime. The molecular free flow defined by the Knudsen diffusion coefficient is integrated through an effective and asymmetrical binary diffusion coefficient. The numerical model is validated with mass flow measurements through microchannels of different cross-section shapes from the near-continuum to the transition regimes, and gas phase separation is studied within a staggered arrangement of spheres. The influence of porosity and mixture composition on the gas separation effect are analyzed. Numerical results highlight the increase in the degree of gas phase separation with the rarefaction rate and the molecular mass ratio. The various simulations also indicate that geometrical features in porous media have a greater impact on gaseous mixtures' effective permeability at highly rarefied regimes. Finally, a permeability enhancement factor based on the lightest species of the gaseous mixture is derived. [ABSTRACT FROM AUTHOR]

"Fluids" presents a Special Issue on "Image-Based Computational and Experimental Biomedical Flows," featuring thirteen research papers that explore the integration of medical imaging data and fluid dynamics for patient-specific cardiovascular flows. The Issue covers topics such as aneurysms, cardiac function, arterial flow, stenosis, and coronary artery interventions. The studies highlight the synergy between computational fluid dynamics, image-based simulations, and experimental setups, offering insights into cardiovascular physiology and pathology. The research aims to revolutionize cardiovascular disease management by providing personalized treatment strategies based on accurate simulations and advanced technologies. [Extracted from the article]

In the present study, the Multi-Relaxation Time Lattice Boltzmann method (MRT-LBM) was employed to solve the airflow inside a scaled room model with dimensions of 0.914x0.457x0.305 m. This room model is considered a representative space with a 1:10 scale to an actual room. The selected room is equipped with a ventilation system. For optimizing the inlet and outlet locations of the airflow, 32 different positions in terms of length, width, and height for the inlet and 4 positions for the outlet were considered. The Taguchi method was utilized for optimizing the inlet and outlet locations, reducing the required number of experiments from 128 to 16. To assess the number of suspended particles, 86400 particles with a size of 1µm were injected into the room. Then, the particle behaviors were examined for a total duration of 60 seconds. The obtained results indicate that the location of the air conditioning system significantly influences the concentration of airborne particles responsible for disease transmission. Utilizing the Taguchi optimization method, optimal positions for the inlet and outlet air were determined to minimize the number of suspended particles in the room (the best position) and maximize it (the worst position). [ABSTRACT FROM AUTHOR]

This study employed Micro X-ray computed tomography (Micro-CT) to reconstruct the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) and used lattice Boltzmann method (LBM) simulations to investigate the dynamic behavior of liquid water in the multiscale space of the GDL and gas channel (GC). The results showed that the transport of liquid water from GDL to GC through the interface of GDL-land and GDL-GC were divided into four stages: large pore filling, through-plane breakthrough, in-plane diffusion, and rapid transport into GC. The wettability of GC wall and GDL affects the transport and distribution of liquid water. When the contact angle on the GC wall was less than 90°, it promoted liquid water transport to the top GC wall, resulting in faster internal flow formation. Conversely, contact angles exceeding 90° caused liquid water to break through the GDL-GC interface from pores away from the GC wall. When the contact angle of the GDL was in the range of 110°–150°, both excessively large and excessively small contact angles hindered water transport and management. Maintaining the contact angle of the GDL around 130° enhanced the breakthrough path and transport speed of liquid water into the GC, and it also reduces localized liquid water accumulation. [Display omitted] • The real structure of GDL was reconstructed by Micro-CT scanning. • The dynamic behavior of liquid water in GDL-GC and their interface is studied by LBM. • The wettability of GC and GDL affects the transport and distribution of liquid water. [ABSTRACT FROM AUTHOR]

The flow field serves as an important component of proton exchange membrane fuel cells (PEMFCs) for maintaining the hydration of the membrane and discharge of excessive water. In this study, a transparent polycarbonate plate was used as the cathode end plate of the PEMFC. The water management capacity of the PEMFCs with different cathode flow fields was evaluated. The movement and evolution patterns of water droplets, film, and columns in different flow fields were analyzed. The results show that liquid water is discharged faster as the cross-section of the flow channel becomes smaller. The performance of the PEMFC with a partially-narrowed flow field is higher due to better water management capacity and forced convection of gas reactant. Liquid water exists mostly in the form of liquid columns in the parallel flow channel, damaging the uniformity of gas distribution. The wavy flow field is likely to be flooded due to the difference of water movement velocity in different channel regions. In addition, a volume of fluid (VOF) model was developed to quantitatively evaluate the water management performance of each type of flow field. The water movement patterns in the different flow channels were concluded. This study provided real-time observations of water movement in the flow channel, revealing a correlation between water management capabilities and the performance of the PEMFC. [ABSTRACT FROM AUTHOR]

A new optimization strategy based on system performance optimization life cycle (SPOLC) is introduced for high-performance lattice Boltzmann simulations of three-dimensional decaying isotropic turbulence. This strategy improves the performance of turbulent flow simulations in periodic boxes at different resolutions using the lattice Boltzmann method (LBM). The strategy improves the performance by modifying the lattice Boltzmann model, mathematical representation, computational algorithm, software implementation, and computing hardware utilization. The modifications include: (1) Establishing the slice concept as a logical grouping layer added to the LBM, applying an aggregation–disaggregation mechanism, enabling two-dimensional (2D) operation on the three-dimensional (3D) model, (2) improving lattice data access pattern by using an alternative one-dimensional (1D) array for numerical representation instead of the 3D cubic representation, (3) major reduction in memory access iterations by switching from function-wise iteration method to lattice-wise iteration method by applying code fusion to the streaming, velocity and collision model functions and iterations, (4) applying process parallelization and data vectorization, (5) achieving a much more efficient utilization of modern compute units by increasing the adaption of stream processing model. Furthermore, a correctness validation process has been applied by conducting lattice-wise value comparisons between the proposed solution output and the original implementation output. Simulations of decaying isotropic turbulence at resolutions ranging from 323 to 5123 using the LBM are carried out for these purposes. Calculations are performed on two systems with distinct specifications, to validate the effectiveness and portability of the SPOLC strategy. The calculation times are significantly reduced after applying the SPOLC strategy on S1 with the lattice Boltzmann relaxation time τ=0.503 by over 69% compared to S2’s original time, increasing to 95.47% at higher resolutions. Different features of the flow fields are depicted and their characteristics are discussed. Thin tubes are visualized, and the energy spectra are studied. All fields are initialized by a forced turbulent field simulated in a previous study using the LBM. [ABSTRACT FROM AUTHOR]

The joint effect of rectangular-type roughness and horizontal vibration on two-dimensional (2D) turbulent Rayleigh–Bénard convection (RBC) is investigated by using the thermal lattice Boltzmann method (LBM) in this article. The present work focuses on the Nusselt number and plume dynamics of the convection in the range of dimensionless vibration frequency 0 ≤ ω* ≤ 1000 and the range of dimensionless roughness height 0 ≤ h* ≤ 0.05. The Rayleigh number is 108 and Prandtl number is 4.38. Our numerical results indicate that the relationship between the Nusselt number and roughness height is mostly proportional, and the relationship between the Nusselt number and the vibration frequency is exponential. It is further found that heat transfer enhances by 3.06 times under the joint effect of horizontal vibration and rectangular roughness on turbulent RBC. It provides significant physical insight into the mechanism of cooperative heat transfer enhancement. [ABSTRACT FROM AUTHOR]

Ion-conducting polymers (Ionomers) are critical in catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and water/vapor-fed electrolyzers, serving essential roles in proton conduction, electronic insulation, and water absorption. This review summarized the physical, chemical and economic parameters of CL ionomers across various PEM modules, focusing on long- and short-side-chain perfluorosulfonic acid (PFSA) ionomers. It also outlines recent efforts in PEM air dehumidification. Characterization methods for ionomer morphology (e.g. rods, swollen clusters, networks) and mass transfer resistance (e.g. ionomer/gas interfacial, catalyst/ionomer interfacial and intra-ionomer) were summarized. Optimal ionomer distribution at electron-proton-gas interfaces is crucial, as proton transfer requiring a thick and connected distribution and gas transport requiring a thin and dispersed distribution. Adjusting ionomer equivalent weight and ratio to catalyst can enhance distribution. Besides, CL ionomer design should emphasize product escape for water electrolyzers and reactant diffusion for vapor ones. Integration of multidimensional and multifunctional techniques, such as visual characterizations of Transmission Electron Microscopy and Nanoscale X-ray computed tomography and numerical simulations of Molecular Dynamics and lattice Boltzmann methods, is recommended for accurate assessment of ionomer behavior. This comprehensive review provides insights into ionomers in CLs, highlighting characterization methods and manipulation strategies, offering guidance for next-generation PEM modules. [ABSTRACT FROM AUTHOR]

Numerical simulation studies of water–rock interaction mechanisms and pore-scale multiphase flow properties often require high computational efficiency and realistic geometries to enable a fast and accurate description of hydrodynamic behavior. In this paper, we have chosen to use deep learning models to achieve these requirements, firstly by using encoder structures to refine the image segmentation of void-solid structures on complex geometries of scanning electron microscopy (SEM) images of porous media through few-shot learning (FSL), not only obtaining an accuracy of 0.97, but also reducing the amount of annotation work. We then focus on pore-scale three-dimensional (3D) structural reconstruction using the unpaired image-to-image translation method, optimizing the cycle-consistent adversarial network (cycle-GAN) model via sliced Wasserstein distance (SWD) to transfer marine sedimentary sandstone features to the initial image, and the geometric stochastic reconstruction problems are transformed into optimization problems. Subsequently, the computational efficiency was improved by a factor of 21 by implementing the lattice Boltzmann simulation method (LBM) accelerated by GPU through compute-unified device architecture (CUDA). The flow field distribution and absolute permeability of the extracted 2D samples and the reconstructed 3D porous media structure were simulated. The results showed that our method could rapidly and accurately reconstruct the 3D structures of a given feature, ensuring statistical equivalence between the 3D reconstructed structures and 2D samples. We solve the problem of extrapolation-based 3D reconstruction of porous media and significantly reduce the time spent on structure extraction and numerical calculations. [ABSTRACT FROM AUTHOR]

Laboratory sciences and disease diagnostics need accelerated medical tests, ease of testing for patients, and lower diagnostic costs. In this respect, one of the most innovative methods is paper-based microfluidic analysis tools, called micro-PAD. Since the chemical-based micro-PADs need sufficient blood to show an accurate blood test, the shape of the micro-PADs, the blood quantity, and the droplet flow to reach the end of the microchannels are important. Therefore, this research showed the liquid droplet motion on a heterogeneous (hydrophobic and hydrophilic) surface using the lattice Boltzmann method, and two star-shaped micro-PADs were modeled to investigate the effect of the droplet size and the droplet deflection from the center of the micro-PAD on liquid flow in microchannels. Based on the obtained results, fluid behavior was similar in two patterns (ten-pointed pattern and four-pointed pattern). This study compared the effects of parallel, convergent, and divergent channels in a four-pointed pattern on fluid velocity. The off-center error of the droplet was considered at the initial moment. The obtained results confirmed the direct relationship between the increased deviation of the center and the lack of uniformity in the fluid penetration. The present simulation results were validated against the laboratory data. [ABSTRACT FROM AUTHOR]

Electric multirotor plant protection unmanned aerial vehicles (UAVs) are widely used in China for efficient and precise plant protection at low altitude for low volumes. Unstructured farmland in China has various types of obstacles, and UAVs usually use a detour path to avoid obstacles due to flight altitude limitations. However, existing UAV spray systems do not spray when in obstacle neighborhoods during obstacle avoidance, resulting in insufficient droplet coverage and reduced plant protection quality in the area. To improve the droplet coverage in obstacle neighborhoods, this article carries out a study of side spray technology with an electric quadrotor UAV, and proposes the design and development of a side spray device. The relationship between the obstacle avoidance path of the UAV and the spray pattern of the side spray device and their effect on droplet coverage in obstacle neighborhoods was explored. An accurate measurement method of the relative position between the UAV and obstacles was proposed. Spray angle calculations and nozzle selection for the side spray device were carried out in conjunction with the relative position. A rotor wind field simulation model was designed based on the lattice Boltzmann method (LBM), and the spatial layout of the side spray device on the UAV was designed based on the simulation results. To explore suitable spray patterns for the side spray device, comparative experiments of droplet coverage in obstacle neighborhoods were carried out under different environments, spray patterns, and flight parameter combinations. The relationship between the flight parameter combinations and the distribution uniformity of droplets and the effective swath width of the side spray device was explored. The experimental results were analyzed by an analysis of variance (ANOVA) and a relationship model was obtained. The results showed that the side spray device can effectively improve droplet coverage in obstacle neighborhoods compared to a device without side spray using the same flight parameter combinations. The effective swath width in obstacle neighborhoods can be increased by a minimum of 6.35%, maximum of 35.32%, and average of 15.25% using the side spray device. The error between the predicted values of the relational model and the field experiment results was less than 15%. The results verify the effectiveness and rationality of the method proposed in this article. This study can provide technical and theoretical references for improving the plant protection quality of UAVs in obstacle environments. [ABSTRACT FROM AUTHOR]

A magnetohydrodynamic lattice Boltzmann method (MHD-LBM) model for a 2D compressible plasma based on the finite volume scheme is established. The double distribution D2Q17 discrete velocities are used to simulate the fluid field. The hyperbolic Maxwell equations, which satisfy the elliptic constraints of Maxwell's equations and the constraint of charge conservation, are used to simulate the electromagnetic field. The flow field and electromagnetic field are coupled to simulate a compressible plasma through the electromagnetic force and magnetic induction equations. Four typical cases, the Taylor vortex flow, strong blast, Orszag–Tang vortex, and one-dimensional Riemann problems, are simulated to validate the MHD-LBM model for a compressible plasma. It is found that shock waves widely exist in a compressible plasma, and strong nonequilibrium effects exist around each shock wave. The quantitative simulation for the Brio–Wu problem demonstrates that this model can easily obtain the physical characteristics of nonequilibrium effects at sharp interfaces (shock waves and detonation waves). The magnetic fields can affect the magnitudes to which the system deviates from its equilibrium state. The viscosity can increase the magnitudes to which the system deviates from its equilibrium state. Compared with existing compressible MHD, these results for nonequilibrium effects can provide mesoscopic physical insights into the flow mechanism of a shock wave in a supersonic plasma. [ABSTRACT FROM AUTHOR]

This study proposes a novel framework of the lattice Boltzmann model for multilayer shallow water equations, considering the mass and momentum exchanges between layers (LABMSWE+). Compared with the original LABMSWE model consisting of N two-dimensional lattice Boltzmann method for shallow water equation (LABSWE) models, the new model includes 1+N LABSWE models. The singular LABSWE model with unit relaxation time is introduced to update the total water depth, and thus, the layer water depths can be obtained explicitly through the fixed layer ratios. The N-layer LABSWE models with the multiple-relaxation-time operator evolve the layer velocities. These two modules are coupled by the total water depth and depth-averaged velocities. The constructed model avoids the freely variable layer thicknesses, which is considered as the main source of the instability. In addition, the mass exchanges enable this model to simulate vertical circulation flows, which are beyond the application of the LABMSWE model. Several numerical tests are then conducted to validate the proposed model. The results show that it exactly satisfies the C-property. In addition, the central difference scheme is more stable and accurate than the upwind and nonequilibrium schemes in the computing of the mass exchanges. The numerical results have an excellent agreement with analytical solutions and reference data, while some unstable and nonphysical results are obtained by the original LABMSWE model. Moreover, the computational time is about 40%–60% of that for the MIKE3, a finite volume solver for the three-dimensional shallow water equations by the Danish Hydraulic Institute. [ABSTRACT FROM AUTHOR]

This study investigates the propagation of sound waves within deep-sea low-sound-speed channels using the lattice Boltzmann method, with a key focus on the influence of depth-dependent sound speed on wave propagation. The depth-variable sound speed condition is realized through the incorporation of an external force proportional to the density gradient. After the model verification, investigations into the two-dimensional spreading of sound sources reveal that the depth-dependent sound speed curves the wave propagation. When source depths differing from the low-sound-speed channel, wave paths deviate due to contrasting speeds above and below. When the sound source is situated within the low-sound-speed channel, waves exhibit converging patterns. The simulations also detail the total reflection behavior of sound waves. When the incident angle falls exceeds the critical angle, the waves remain intact within the low-sound-speed channel, thereby enabling the preservation of high amplitude acoustic signals even at remote locations. The subsequent simulations of sound wave propagation around obstacles demonstrate that the low-sound-speed channel also exhibits better signal transmission capabilities in the presence of obstacles. In a uniform sound speed environment, acoustic wave propagation around a submarine exhibits a symmetric pattern. By contrast, under depth-evolving speed conditions, submarines operating at various depths manifest distinct propagation characteristics, such as asymmetric wave propagation during shallow diving, as well as wave attenuation or even silencing when cruising within low-sound-speed channels. These findings underscore the profound implications of depth-evolving sound speed on underwater acoustic signal detection and transmission. [ABSTRACT FROM AUTHOR]

The natural circulation loop is crucial for the safe and stable operation of nuclear reactors and other applications. Traditional numerical algorithms, based on the Boussinesq approximation, have limitations when dealing with large temperature differences and density disparity, and they do not fully address fluid compressibility. This paper adopts the decoupled and stabilized lattice Boltzmann method (DSLBM) with a non-Boussinesq algorithm to study the natural circulation loop. The DSLBM provides a detailed flow description under large temperature and density differences, incorporating the pseudopotential multiphase model, temperature equation, and state equation, without relying on assumptions. The study examines the loop's performance under various temperature differences, central height differences, and heating source lengths, focusing on mass flow rate, driving head, and heating power. It reveals the energy performance, flow characteristics, and heat transfer properties of the loop, highlighting the physical mechanisms involved. Comparison with the empirical formulation of the incompressible equation from the theoretical aspect shows that when the temperature difference coefficient is lower than 0.15, the two methods are not much different from each other. When the temperature difference coefficient reaches 0.2, 0.3, and 0.4, the difference between the two methods is 9.47%, 19.11%, and 42.64%, respectively. Consequently, the Boussinesq approximation can be compensated by DSLBM, which proves the value of the application of the algorithm in exploiting the compressibility of fluids. The dimensionless fitting correlation with greater universality is obtained, which helps to predict the properties of the natural circulation loop with varying temperature differences, friction coefficients, and geometric structures. The research in this paper will lay the foundation for optimizing the system design of the natural circulation loop and improving energy utilization efficiency. [ABSTRACT FROM AUTHOR]

Computation of impulsively started flows presents difficulties associated with the presence of a singularity at time equal to zero. When using the lattice Boltzmann method, the standard practice is to start the computation from a potential flow field that is not part of the solution. A different approach to the problem is presented in this article where three new criteria for the selection of computational parameters in highly unsteady flow environments are presented. These criteria, which do not overrule the conventional one that sets limits to the computational Mach number, are based on fluid physics considerations. They represent additional constrains related to (a) the distance traveled by sound waves at early times, (b) the importance of viscous length during the onset of impulsive motion, and (c) the presence of spurious reflected pressure waves at the beginning of computations. The proposed methodology was tested in the case of an impulsively started cylinder, and the results were compared to those of analytical, numerical, and experimental nature published in specialized literature. It is intended that this study facilitates the computation of highly unsteady flows for researchers who use the lattice Boltzmann method. [ABSTRACT FROM AUTHOR]

Complex composition and intricate pore-scale structure of frozen soils poses significant challenges in reliably and efficiently obtaining their permeability. In this study, we propose a modified quartet structure generation set (QSGS) numerical tool for generating frozen soils and present the development of a computational simulation code based on the multiple-relaxation-time lattice Boltzmann method (LBM). In the modified QSGS, the arc-shaped water-ice interface is depicted, and the influence of pore-scale geometry on freezing temperature is considered. The validity of combining the proposed QSGS model and the LBM code is proved by comparing calculated results to analytical and experimental results of porous media. Our objective was to investigate the effects of soil features, including porosity, grain diameter, shape anisotropy of soil particles, and ice content on the intrinsic permeability of frozen soil. Additionally, we examined the relationship between these features and the specific surface area and tortuosity. Numerical results show that the intrinsic permeability of frozen soils increases with increasing porosity, larger granular diameter, and anisotropy, which is identical with the pressure gradient. The presence of ice led to clogging flow pathways and drastically decreased the intrinsic permeability, which is significantly less than unfrozen soil with same effective porosity. This study provides a useful tool to investigate the intricate interplay between the pore-scale structure and the intrinsic permeability of frozen soils. [ABSTRACT FROM AUTHOR]

The flow boiling heat transfer in microchannels has been extensively used in engineering due to its high heat dissipation with a small temperature difference. This study employs a hybrid method to numerically investigate the effects of a flow-induced vibrating cylinder on enhancing the subcritical boiling heat transfer in microchannels. The hybrid approach integrates the pseudopotential multiphase lattice Boltzmann method for modeling unsteady flows, the finite difference method for solving the heat transfer equation, and the immersed boundary method for handling the boundary condition at the fluid–cylinder interface. Flow boiling simulations in the microchannel are performed for three setups: a smooth vertical channel, a vertical channel with a stationary cylinder, and a vertical channel with a flexibly supported cylinder. Simulations have been conducted by varying the Reynolds number based on the diameter of the cylinder (R e d ) from 35 to 333.3, the dimensionless boiling number (Bo) from 0.001 84 to 0.045 97, and blockage ratio (BR) of 3.0, 4.0, and 5.0. It is found that the vortical wake of the cylinder is important in enhancing the heat transfer in microchannels, which is quantified by the (R e d ). Specifically, when R e d < 48.0 , both stationary and flexibly supported cylinders have almost the same effect on heat transfer during the flow boiling process, as there is no vortex shedding from both cylinders; when 48.0 ≤ R e d < 68.2 , the flexibly supported cylinder achieved higher enhancement than the stationary cylinder, which is due to the vortical wake generated by the flow-induced vibration in a subcritical Reynolds number regime; when 68.2 ≤ R e d , both stationary and flexibly supported cylinders have comparable effect on the rates of heat transfer, because both cylinders generate similar vortical wakes. Flow field analysis indicates that the disturbance due to the vortex wakes on the thermal boundary and/or the vapor insulation layer is the mechanism of the heat transfer enhancement in channels. [ABSTRACT FROM AUTHOR]

The hydrodynamic interaction between two chiral organisms (chirality parameter 0 ≤ C2 ≤ 10) swimming toward each other is investigated using the lattice Boltzmann method over a Reynolds number range of 0.01 ≤ Re ≤ 5, with the swimming parameter β = ±5. Our findings reveal that in a finite inertial flow regime, with a low C2 for chiral squirmers, enhancing the C2 leads to a strengthened attraction between pullers (a type of squirmer) and other chiral squirmers. Simultaneously, this strengthening reduces the repulsive tendencies observed in pushers (another type of squirmer). Beyond a certain threshold (C2 ≥ 5), an increase in the C2 causes the flow field generated by a pusher to resemble that of a puller, there by initiating an attractive influence on another squirmer. At this point, with an increase in C2, the mutual attraction between pullers and pushers intensifies. Moreover, as the C2 continues to increase, the duration of the intense interaction between colliding pullers or pushers steadily diminishes, contrasting with the increased duration of the intense interaction between non-colliding pushers. These empirical insights substantively enhance our comprehension and empirical investigation of collective behavioral dynamics in chiral microorganisms. [ABSTRACT FROM AUTHOR]

In recent decades, a paradigm shift in macroscopic methods has favored the use of non-primitive variables, such as velocity and vorticity (V–V), over traditional primitive variables. This shift eliminates the need for solving a Poisson equation for pressure, aligning numerical treatments more closely with physical reality. However, the lattice Boltzmann method (LBM), renowned for its efficacy in studying fluid flow phenomena, continues to rely on the conventional pressure–velocity (P–V) approach. This conventional approach necessitates a pressure–density relation, posing challenges in maintaining the incompressible condition. This study pioneers a novel application of the LBM to three-dimensional velocity–vorticity equations, expanding upon our suggested recent method for two-dimensional cases [Kefayati, Phys. Fluids. 36, 013128 (2024)]. To address the complexities introduced by the vortex stretching term in three dimensions, a new equilibrium distribution function is formulated and introduced to the three-dimensional nature of the vorticity vector. The paper details the derivation of the three-dimensional LBM and substantiates its effectiveness through numerical examples, showcasing its applicability in fluid dynamics. By bridging the gap between traditional P–V formulations and the benefits of non-primitive V–V variables, this work contributes to the ongoing exploration of LBM applications in fluid dynamics. The focus on three-dimensional scenarios involving velocity–vorticity equations marks a significant advancement, offering insights into the nuanced dynamics of fluid flow and paving the way for more accurate and realistic simulations in complex environments. [ABSTRACT FROM AUTHOR]

The laying process is crucial in using stereolithography (SL) for molding Al2O3 parts. However, most studies focus on the laying process of macroscopic slurry; there needs to be more focus on microscopic exploration. Studying from a microscopic perspective can help us understand the influence of its parameters on droplet spreading and infer the macroscopic changes of the slurry based on the changes in droplet spreading to understand why parameters cause macroscopic changes in the slurry. A pseudopotential model based on Sisko's non-Newtonian behavior in lattice Boltzmann method is proposed to study the spreading process of droplets and validated using wetting characteristics. The previous layers of the platform and the printed solid are investigated to understand the effect of laying velocity on the spreading diameter, the thickness, and the both-sided contact angles. The results indicate that a higher laying velocity leads to a larger spreading diameter, a smaller spreading thickness, and a smaller left contact angle. However, it also increases the contact angle difference between the two sides, leading to uneven slurry. The droplet spreads more unevenly when the previous laying surface is the printed solid. At the same velocity, the droplet spreads with a smaller diameter, thicker thickness, and larger contact angle on the printed solid surface. Therefore, a higher laying velocity in the SL laying process is not recommended, especially when the front layer is a printed solid. Although a higher laying velocity will increase the laying area and reduce laying time, it will cause protrusions at the front edge, and inconsistent laying thickness of the same layer will affect the following photosensitive curing process. The Harris Hawks optimization-generalized regression neural network algorithm is proposed and compared with other common artificial intelligence algorithms to predict the spreading parameters. The comparison shows that the proposed algorithm provides a more stable and accurate prediction of spreading parameters. [ABSTRACT FROM AUTHOR]

In this paper, we used the multi-relaxation time lattice Boltzmann method to investigate natural convection in a triangular-shaped cavity filled with a tri-hybrid nanofluid. The cavity is partially heated by a chip of fixed size (l = L / 2), the position of which varies on the left and bottom walls in order to find the optimal positions. The inclined side is maintained at a cool temperature, while the other parts are adiabatic. A detailed analysis is carried out on the impact of four essential parameters on the optimization of heat transfer: the Rayleigh number, ranging between Ra = 103 and Ra = 106; the partial heating position, showing the cavity in six different configurations; the fluid type, including pure water, nanofluid, hybrid nanofluid, and tri-hybrid nanofluid; and finally, the volume concentration of the nanoparticles for three values, ϕ = 0%, 3%, and 6%. Results are presented in the form of isotherms, streamlines, temperature and velocity profiles, and the mean Nusselt number values. As the results show, the position of the partial heater plays a crucial role, influencing natural convection heat transfer significantly in certain positions at all values of the Rayleigh number. The type of fluid has a remarkable impact on the amplification of natural convection at large values of the Rayleigh number, where the buoyancy force becomes strong. Notably, the use of tri-hybrid nanofluid shows a clear improvement in natural convection heat transfer. Furthermore, a substantial increase in thermal transmittance is observed with an increasing nanoparticle volume fraction. The validation results agree well with both numerical results and experimental data published in the literature. [ABSTRACT FROM AUTHOR]

C++ template metaprogramming has emerged as a prominent approach for achieving performance portability in heterogeneous computing. Kokkos represents a notable paradigm in this domain, offering programmers a suite of high-level abstractions for generic programming while deferring much of the device-specific code generation and optimization to the compiler through template specializations. Kokkos furnishes a range of device-specific code specializations across multiple back ends, including CUDA and HIP. Diverging from conventional back ends, the OpenACC implementation presents a high-level, multicompiler, multidevice, and directive-based programming model. This paper presents recent advancements in the OpenACC back end for Kokkos (i.e., KokkACC) and focuses on its integration into the Kokkos ecosystem, exploration of automatic device selection capabilities to enhance productivity, and performance evaluation on modern hardware such as NVIDIA H100 GPUs. The study includes implementation details and a thorough performance assessment across various computational benchmarks, including minibenchmarks (AXPY and DOT product), miniapps (LULESH, MiniFE, and SNAP-LAMMPS), and a scientific kernel based on the lattice Boltzmann method. [ABSTRACT FROM AUTHOR]

The space fractional advection–diffusion equation is a crucial type of fractional partial differential equation, widely used for its ability to more accurately describe natural phenomena. Due to the complexity of analytical approaches, this paper focuses on its numerical investigation. A lattice Boltzmann model for the spatial fractional convection–diffusion equation is developed, and an error analysis is carried out. The spatial fractional convection–diffusion equation is solved for several examples. The validity of the model is confirmed by comparing its numerical solutions with those obtained from other methods The results demonstrate that the lattice Boltzmann method is an effective tool for solving the space fractional convection–diffusion equation. [ABSTRACT FROM AUTHOR]

During solar cell operation, most light energy converts to heat, raising the battery temperature and reducing photoelectric conversion efficiency. Thus, lowering the temperature of solar cells is essential. Nanofluids, with their superior heat transfer capabilities, present a potential solution to this issue. This study investigates the mechanism of enhanced heat transfer by nanofluids in two-dimensional rectangular microchannels using the two-phase lattice Boltzmann method. The results indicate a 3.53% to 22.40% increase in nanofluid heat transfer, with 0.67% to 6.24% attributed to nanoparticle–fluid interactions. As volume fraction (φ) increases and particle radius (R) decreases, the heat transfer capability of the nanofluid improves, while the frictional resistance is almost unaffected. Therefore, the performance evaluation criterion (PEC) of the nanofluid increases, reaching a maximum value of 1.225 at φ = 3% and R = 10 nm. This paper quantitatively analyzes the interaction forces and thermal physical parameters of nanofluids, providing insights into their heat transfer mechanisms. Additionally, the economic feasibility of nanofluids is examined, facilitating their practical application, particularly in solar cell cooling. [ABSTRACT FROM AUTHOR]

In this work, the doubly periodic shear layers are employed to underpin the vortex dynamics associated with the perturbed free shear layers using the lattice Boltzmann method with the Bhatnagar–Gross–Krook collision model. The effect of (i) width between shear layers, (ii) modes of perturbation, (iii) the strength of perturbation, and (iv) thickness of a shear layer on roll-up formation, vortex interactions, pairings, and the generation of thin filaments is studied in detail with the evolution kinetic energy, enstrophy, and palinstrophy for Reynolds number, Re = 30 , 000 . The formation of thin vorticity braids and vortex merging causes the production of vorticity gradients and a rise in the palinstrophy. No compelling interplay is observed with corotating or counter-rotating vortices for a minimum separation distance ( S 1 ) between two opposite vorticity strips. The counter-force from each layer creates a jet whose properties differ from those of a single shear layer. However, the evolution of multiple pairs of shear layers produces smaller vortices of lower strength and enhances the growth of palinstrophy and decay of kinetic energy and enstrophy. The rise in the momentum thickness is observed for the interactive flows ( S 2 ≤ S 1 ), while the non-interactive flow ( S 2 > S 1 ) shows constant momentum thickness. The increased perturbation strength quickens the roll-up of shear layer and enhances the growth of palinstrophy. Thick shear layers evolves with dipole-like structures and slows down the decay of kinetic energy and enstrophy compared to thin shear layer flows. It generates family of thin vortex filaments and influences the rapid growth of vorticity gradients and positive Okubo–Weiss-Q-quantity. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to analyze the mechanism of nanofluid enhanced heat transfer in microchannels and promote the application of nanofluids in industrial processes such as solar collectors, electronic cooling and automotive batteries. Design/methodology/approach: The two-phase lattice Boltzmann method was used to calculate the flow and heat transfer characteristics of Al2O3 nanofluids in a microchannel at Re = 50. By comparing the simulation results of pure water, nanofluids without calculated nanoparticle-fluid interaction forces and nanofluids with calculated nanoparticle-fluid interaction forces, the effects of physical properties improvement and interaction forces on flow and heat transfer are quantified. Findings: The findings show that the nanofluid (φ = 3%, R = 10 nm) increases the average Nusselt number by 22.40% at Re = 50. In particular, 16.16% of the improvement relates to nanoparticles optimizing the thermophysical parameters of the base fluid. The remaining 6.24% relates to the disturbance of the thermal boundary layer caused by the interaction between nanoparticles and the base fluid. Moreover, the nanoparticle has a negligible effect on the average Fanning friction factor. Ultimately, we conclude that the nanofluid is an excellent heat transfer working medium based on its performance evaluation criterion, PEC = 1.225. Originality/value: To the best of the authors' knowledge, this research quantifies for the first time the contribution of nanoparticle-liquid interactions and nanofluids physical properties to enhanced heat transfer, advancing the knowledge of the nanoparticle's behavior in liquid systems. [ABSTRACT FROM AUTHOR]

Tsunamis, though infrequent, wield devastating power on coastal regions, necessitating accurate simulation techniques to comprehend their impact and enhance disaster preparedness. Despite significant advances in modern computational fluid dynamics, these simulations continue to pose considerable challenges, including numerical intricacies and substantial computational costs. Owing to its remarkable computational efficiency and high performance, the lattice Boltzmann method (LBM) is being increasingly used for simulating large-scale tsunamis. This review paper systematically surveys the application of the free-surface flow model using the LBM to simulate tsunamis, covering its theoretical underpinnings, numerical implementation, and validation against real-world events. Furthermore, the paper discusses challenges, limitations, and ongoing developments in the application of the LBM for tsunami simulations, elucidating avenues for future research. By amalgamating insights from diverse studies, this review underscores the role of the LBM as a tool for advancing our understanding of tsunamis and increasing coastal resilience. HIGHLIGHTS: Lattice Boltzmann method investigated for tsunami simulations Challenges, limitations, and ongoing developments in tsunami simulation discussed Systematical survey of the application of the free-surface flow model Theoretical underpinning, numerical implementation, and real-world validation [ABSTRACT FROM AUTHOR]

The three-dimensional lattice Boltzmann method (LBM) is used to simulate the motion of a spherical squirmer in a square tube, and the steady motion velocity of a squirmer with different Reynolds numbers (Re, ranging from 0.1 to 2) and swimming types is investigated and analyzed to better understand the swimming characteristics of microorganisms in different environments. First, as the Reynolds number increases, the effect of the inertial forces becomes significant, disrupting the squirmer's ability to maintain its theoretical velocity. Specifically, as the Reynolds number increases, the structure of the flow field around the squirmer changes, affecting its velocity of motion. Notably, the swimming velocity of the squirmer exhibits a quadratic relationship with the type of swimming and the Reynolds number. Second, the narrow tube exerts a significant inhibitory effect on the squirmer motion. In addition, although chirality does not directly affect the swimming velocity of the squirmer, it can indirectly affect the velocity by changing its motion mode. [ABSTRACT FROM AUTHOR]

Flow past bluff bodies like square cylinders is important in engineering applications, but flow patterns behind staggered cylinder arrangements remain poorly understood. Existing studies have focused on tandem or side-by-side configurations, while offset orientations have received less attention. The aim of this paper is to numerically investigate flow dynamics and force characteristics behind two offset square cylinders using the single relaxation time lattice Boltzmann method. The effects of changing both the Reynolds number (Re = 1-150) and gap spacing ratio (g* = 0.5-5) between the cylinders are analyzed. Instantaneous vorticity contours, time histories of drag and lift coefficients, power spectra of lift, and force statistics are used to characterize the flow. Different flow regimes have been identified in various ranges of Re and g* - including steady, chaotic, flip-flopping, single-bluff body, and fully developed flows. Larger spacings led to more regular vortex dynamics and force statistics. Smaller spacings promoted complex interactions and modulated forces. Offset cylinder orientation and spacing significantly influence flow features in staggered arrangements. The findings provide new modalities for controlling fluid dynamics past bluff bodies by tuning Re and gap parameters. [ABSTRACT FROM AUTHOR]

This study investigates corner solidification in a closed cavity in which the left and bottom walls are kept at a temperature lower than its initial temperature. The liquid material in the cavity initially lies at its phase transition temperature and, due to cold boundary conditions at the left–bottom walls, solidification starts. The simulation of corner solidification was performed using a kinetic-based lattice Boltzmann method (LBM), and the tracking of the solid–liquid interface was captured through the evaluation of time. The present investigation addresses the effect of natural convection over conduction across a wide range of higher Rayleigh numbers, from 106 to 108. The total-enthalpy-based lattice Boltzmann method (ELBM) was used to observe the thermal profiles in the entire cavity with a two-phase interface. The isotherms reveal the relative dominance of natural convection over conduction, and the pattern of interface reveals the effective growth of the solidified layer in the cavity. To quantify the uniformity of cooling, a coefficient of variation (COV) for the thermal field was calculated in the effective solidified zone at a wide range of Ra. The results show that the value of COV increases with Ra and reduces with time. The thermal instability in the flow field is also quantified through FFT analyses. [ABSTRACT FROM AUTHOR]

Applying numerical simulation technology to investigate fluid-solid interaction involving complex curved boundaries is vital in aircraft design, ocean, and construction engineering. However, current methods such as Lattice Boltzmann (LBM) and the immersion boundary method based on solid ratio (IMB) have limitations in identifying custom curved boundaries. Meanwhile, IBM based on velocity correction (IBM-VC) suffers from inaccuracies and numerical instability. Therefore, this study introduces a high-accuracy curve boundary recognition method (IMB-CB), which identifies boundary nodes by moving the search box, and corrects the weighting function in LBM by calculating the solid ratio of the boundary nodes, achieving accurate recognition of custom curve boundaries. In addition, curve boundary image and dot methods are utilized to verify IMB-CB. The findings revealed that IMB-CB can accurately identify the boundary, showing an error of less than 1.8% with 500 lattices. Also, the flow in the custom curve boundary and aerodynamic characteristics of the NACA0012 airfoil are calculated and compared to IBM-VC. Results showed that IMB-CB yields lower lift and drag coefficient errors than IBM-VC, with a 1.45% drag coefficient error. In addition, the characteristic curve of IMB-CB is very stable, whereas that of IBM-VC is not. For the moving boundary problem, LBM-IMB-CB with discrete element method (DEM) is capable of accurately simulating the physical phenomena of multi-moving particle flow in complex curved pipelines. This research proposes a new curve boundary recognition method, which can significantly promote the stability and accuracy of fluid-solid interaction simulations and thus has huge applications in engineering. Graphic Abstract [ABSTRACT FROM AUTHOR]

This paper addresses the need for an efficient and adaptable approach to solve linear acoustic wave equations in the lattice Boltzmann method (LBM). A novel lattice-adaptive model is introduced, derived through a Chapman–Enskog analysis, which utilizes a single relationship for the equilibrium distribution function across all lattice structures. The intended derivation begins by considering a standard equilibrium distribution function with unknown coefficients. By selecting the displacement of the acoustic wave as the zero-order microscopic moment, accurate recovery of the macroscopic wave equation is ensured. Unlike existing methods, the model simplifies the complexity associated with equilibrium distribution functions and offers greater versatility. The model is validated through extensive benchmark testing on one and two-dimensional wave propagation problems. Results demonstrate excellent agreement with analytical solutions, with maximum root mean square errors of 10-3 (<0.1% error) and minimum errors of 10-6 (<0.0001% error), indicating high predictive accuracy (>99.9%). Additionally, the model exhibits second-order spatial accuracy, with the relative error norm E_2 displaying slopes close to 2, signifying a spatial accuracy of second order. The numerical simulations show a decrease in errors as the mesh size becomes more refined. [ABSTRACT FROM AUTHOR]

Several numerical simulations of fluid flow were performed using the Lattice Boltzmann method and image processing techniques to estimate the effective properties of 2-D porous rocks. The effective properties evaluated were the physical characteristics that allow fluid flow including the effective porosity, permeability, tortuosity, and average throat size to determine the storage and transport of fluids in porous rocks. The permeability was compared using the Darcy model simulation and the empirical Kozeny–Carman Equation. The results showed that the Lattice Boltzmann method and image processing techniques can estimate the effective parameters of porous rocks. Furthermore, there was a good correlation between permeability and parameters such as effective porosity, tortuosity, and average throat size. The Darcy model simulation revealed a gamma distribution in the permeability, while the empirical Kozeny–Carman Equation showed a log-normal distribution. [ABSTRACT FROM AUTHOR]

This study addresses the critical challenge of excessive water production in mature oil and gas reservoirs. It focuses on the effectiveness of polymer gel injection into porous media as a solution, with an emphasis on understanding its impact at the pore scale. A step-wise Lattice Boltzmann Method (LBM) is employed to simulate polymer gel injection into a 2D Berea sample, representing a realistic porous media. The non-Newtonian, time-dependent characteristics of polymer gel fluid necessitate this detailed pore-scale analysis. Validation of the simulation results is conducted at each procedural step. The study reveals that the methodology is successful in predicting the effect of polymer gel on reducing permeability as the gel was mainly formed in relatively larger pores, as it is desirable for controlling water cut. Mathematical model presented in this study accurately predicts permeability reductions up to 100% (complete blockage). In addition, simulations conducted over a wide range of gelation parameters, TD_factor from 1 to 1.14 and Threshold between 0.55 and 0.95, revealed a quadratic relationship between permeability reduction and these parameters. The result of this research indicates LBM can be considered as promising tool for investigating time-dependant fluids on porous media. [ABSTRACT FROM AUTHOR]