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This study aims to investigate the effectiveness of the lattice Boltzmann method (LBM) in studying the scattering of electromagnetic waves by curved and complex surfaces. The computation of Maxwell's equations is done by solving for a pair of distribution functions, which evolve based on a two-step process of collision and streaming. LBM bypasses the need for expansion via vector spherical harmonics and thus is amenable to scatterers with complex geometries. We have employed LBM to compute the scattering width and radiation force for perfect electrically conducting and dielectric cylinders of circular and elliptical cross sections. Both smooth and corrugated surfaces are studied, and the results are compared against known analytical and numerical solutions from other methods. To ensure the broad applicability of the method, we have explored a wide range of parameter space—the dielectric constant and particle size to the wavelength ratio spanning Rayleigh, Mie, and geometrical optics regimes. Our simulations have successfully reproduced well-known analytical and numerical solutions, confirming the accuracy and reliability of the LBM for scattering calculations by complex-shaped objects. [ABSTRACT FROM AUTHOR]

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 anode porous transport layer (APTL) has a significant impact on oxygen and liquid water transport in proton exchange membrane electrolysis cells (PEMEC), especially the efficient discharge of oxygen. This paper points out the relevant transport losses dominated by the gas-liquid flow characteristics of the APTL in PEMEC, and review the research content and application limitations of four methods, namely, optical visualization, microfluidic platform visualization, fluid-volume method and lattice Boltzmann method, based on the current experimental and numerical simulation applications in the APTL. Based on the flow patterns in the flow channel and the characteristics of gas-liquid mass transfer and oxygen bubble transport in the APTL pore channel observed by different research methods, the importance of comprehensively improving the structural parameters, performance, operating conditions and mathematical model of APTL to reduce the transport loss and improve the performance of PEMEC at high current densities is clarified. Finally, it is pointed out that visualization technology, numerical simulation and electrochemical detection should be coupled based on the research scale and direction to promote the breakthrough and innovation of APTL in future research. • Influence of gas-liquid flow characteristics on mass transport losses in PEMEC. • Visualization of two-phase transport in APTL and flow channels. • Overview the research focus of different numerical simulation methods. • An in-depth investigation of possible methods to improve gas-liquid flow in PEMEC. [ABSTRACT FROM AUTHOR]

The microstructure of the porous anode plays a crucial role in the mass transfer dynamics and electrochemical reaction of solid oxide fuel cells (SOFCs), significantly impacting their performance. This paper investigates the effect of microstructure of the porous anode on mass transfer and electrochemical reaction in SOFCs, which addresses the scarcity of research due to the complexity of microstructure modeling, offering supportive information for the structure optimization of SOFCs. Firstly, theoretical deductions of constructing microstructure and simulating mass transfer are conducted. Subsequently, a construction model is established based on the fractional Brownian motion (FBM) model to obtain different microstructures, encompassing various flow pore structures, triple phase boundary (TPB) structures, and inlet structures. Through a finite difference lattice Boltzmann method (LBM), the mass transfer is modeled to predict gas molar fraction distributions and calculate concentration overpotentials with different microstructures. Finally, thorough experiments are carried out to analyze the effect of structural parameters on mass transfer and electrochemical reaction. Taking the hydrogen-steam-nitrogen (H2-H2O-N2) ternary mass transfer as an example, the comparison results indicate that complex flow pore structures increase both the distance and resistance of mass transfer. To improve the performance of SOFCs, reducing flow pore complexity and increasing TPB length both mitigate the effect of concentration polarization. Moreover, the change of inlet structure suggests minimal impact on mass transfer and electrochemical reaction. [ABSTRACT FROM AUTHOR]

To understand, predict and control the motion of the solid particles, the motion of a neutrally buoyant circular particle with thermal convection in a square cavity is studied with the lattice Boltzmann method, where the effects of the initial position of the circular particle, Rayleigh number and particle size are investigated. Under the effect of thermal convection, the obvious feature of the motion of the circular particle in the square cavity is the existence of the limit cycle, which is created by the inertia of the circular particle, confinement of the boundaries of the square cavity and centrifugal force. Interestingly, the limit cycle is insensitive to the initial position of the circular particle. The effect of the Rayleigh number on the motion of the circular particle is obvious, with the increase of the Rayleigh number, the limit cycle expands toward the boundaries of the square cavity first, then shrinks and migrates toward the bottom left corner, which is caused by the combined effects of the centrifugal force and vortex behavior. The effect of the particle size on the motion of the circular particle is significant, with the increase of the particle size, the inertia of the circular particle becomes larger, which is more difficultly dragged by the fluid, thus, the limit cycle shrinks toward the bottom left corner of the square cavity. [ABSTRACT FROM AUTHOR]

BACKGROUND: As unmanned aerial spraying systems (UASS) usage grows rapidly worldwide, a critical research study was conducted to optimize the simulation of UASS applications, aiming to enhance pesticide delivery efficiency and reduce environmental impact. The study examined several key aspects for accurate simulation of UASS application with lattice Boltzmann method (LBM). Based on these discussions, the most suitable grid size and simulation parameters were selected to create a robust model for optimizing UASS performance in various pest management scenarios, potentially leading to more targeted and sustainable pest control practices. RESULTS: The effect of stability parameter, grid size around the rotor and near ground, and parameters at wake flow were carefully analyzed to improve the precision of pesticide drift predictions and deposition patterns. Optimal grid sizes were identified as 0.2 m generally, 0.025 m near rotors, and a 0.1 + 0.2 m scheme for ground proximity, with finer grids improving accuracy but increasing computation time. Wake resolution and threshold significantly influenced simulation results, while wake distance had minimal impact beyond a certain point. The LBM's accuracy was validated by comparing simulated downwash flow and droplet deposition with field test data. CONCLUSION: This study optimized UASS simulation parameters, balancing computational efficiency with accuracy. The validated model enhances our ability to design more effective UASS for pest management, potentially leading to more precise and targeted pesticide applications. These advancements contribute to the development of sustainable pest control strategies, aiming to reduce pesticide usage and environmental impact while maintaining crop protection efficacy. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This paper proposes a performance-based microstructure design methodology specifically tailored for gas diffusion layers (GDLs). The generative machine learning denoising diffusion probabilistic model (DDPM) is trained and used for performance-based microstructure design. This study demonstrates significant progress in performance-based design by incorporating DDPM into the microstructure design process, offering a promising approach for GDL microstructure design. This methodology provides the advantage of generating 2D microstructures with desired permeability and volume fractions. Moreover, it is not limited to a specific performance criterion, making it adaptable to target other metrics. To train the DDPM, a 2D GDL microstructure dataset is constructed using the Lattice Boltzmann Method (LBM) for permeability estimation. Subsequently, we employ the DDPM with U-net architecture, which leverages positional encoding to learn the microstructure's volume fraction and permeability effectively. The input label pair of permeability and volume fraction is generated considering the inherent relationship between these two parameters to ensure the generation of meaningful microstructures. This relationship is supposed to ensure that the resulting microstructures align with realistic and physically meaningful characteristics. The simulated performance results obtained from the generated microstructures using the proposed methodology demonstrate a strong consistency with the targeted performance objectives. [ABSTRACT FROM AUTHOR]

The thermal lattice Boltzmann method (TLBM) is used to analyze the overall performance for upstream and downstream wedge ribs microchannels (MC) under slip flow conditions. The thermal–hydraulic enhancement criterion is investigated to evaluate the performance of the channel and compare it for various roughness MC. In order to improve the channel performance, two alternative artificial roughness geometry, upstream and downstream wedge ribs, are taken both on the top and bottom walls of the microchannel with aspect ratio (AR) 7, where AR = L/H; L and H are channel length and height respectively in micrometer (μm). This study focused on simulating temperature profiles, velocity vectors in terms of stream lines, pressure gradients, and friction factor in terms of Poiseuille number as well as heat transfer rate in terms of Nusselt number (Nu). The overall performance of the channel is calculated based on flow friction and heat transfer rate for different Knudsen numbers (Kn) ranging from 0.01 to 0.10 with upstream and downstream wedge ribs height up to 20% of channel height. The results have been compared with previously published work and are found a very good agreement. The analysis revels that, the vortices are formed behind each upstream wedge rib, whereas they are created in front of each downstream wedge rib. The size and shape of vortices are influenced by Kn. As Kn increases from 0.0 to 0.10, the fluid circulation area becomes smaller for upstream wedge ribs MC, while it is changing very slowly for downstream wedge ribs MC; hence, the pressure gradient is also responsible for changing Kn. The flow friction is linearly decreased with increasing Kn but significantly increased with ribs height. But compared to the smooth channel, the friction is significantly increased for upstream and downstream wedge ribs MC. The average rate of heat transfer in terms of Nu is also linearly decreased with increasing Kn, but Nu increased with ε for lower Kn and decreased for higher Kn. Therefore, compared to smooth MC, Nu increased and decreased for the same for upstream and downstream wedge ribs MC. Finally, the performance enhancement (η) is calculated, and it is found that η decreased with increasing Kn for upstream and downstream wedge ribs MC. The higher performances are indicated for lower Kn as well as lower ribs height. For all cases, the better performance is noted for downstream wedge ribs MC compared to upstream MC. [ABSTRACT FROM AUTHOR]

The article "Vibration-induced morphological evolution of a melting solid under microgravity" in the Journal of Fluid Mechanics examines the melting of a solid under microgravity conditions due to lateral vibrations. The study uses numerical simulations to show a shift in flow structure from periodic circulation to a columnar regime as melting occurs. The research delves into the influence of columnar thermal plumes and peripheral flow on the morphological evolution of the liquid-solid interface. Additionally, it discusses the merging of columnar plumes and the evolution of interface roughness amplitude in microgravity vibroconvection. The findings shed light on the impact of vibration-induced melting on solid phase morphology and offer insights for controlling melting processes in microgravity environments, with potential applications in space exploration. [Extracted from the article]

Proton exchange membrane fuel cells (PEMFCs) are being pursued for applications in the maritime industry to meet stringent ship emissions regulations. Further basic research is needed to improve the performance of PEMFCs in marine environments. Assembly stress compresses the gas diffusion layer (GDL) beneath the ribs, significantly altering its pore structure and internal transport properties. Accurate evaluation of the PEMFC cathode's electrochemical performance at the pore scale is critical. This study employs a three-dimensional multicomponent gas transport and electrochemical reaction lattice Boltzmann model to explore the complex interplay between GDL compression and factors such as overpotential, pressure differential, porosity, and porosity gradient on PEMFC performance. The findings indicate that compression accentuates the reduction in oxygen concentration along the flow path and diminishes the minimum current density. Furthermore, compression exacerbates the reduction in current density under varying pressure conditions. Increased local porosity near the catalyst layer (CL) enhances oxygen accessibility and water vapor exclusion, thereby elevating the mean current density. Sensitivity analysis reveals a hierarchy of impact on mean current density, ranked from most to least significant: overpotential, porosity, compression, porosity gradient, and pressure difference. These insights into the multicomponent gas transfer dynamics within compressed GDLs inform strategic structural design enhancements for optimized performance. [ABSTRACT FROM AUTHOR]

Metallic foams have become a cutting-edge solution for many thermal management problems. These are of interest by thermal research community because of the cellular structure and have gas-filled pores inside a metal matrix. Due to the uniqueness in their structure, they exhibit good performance in boiling heat transfer because of the properties such as higher specific surface area, large number of nucleation sites, wettability characteristics, and capillary action. The boiling heat transfer over metal foam is a complex phenomenon, greatly affected by the thickness, porosity, and pores per inch (PPI) of metal foam along with the thermo-physical properties of the foam and boiling liquid. By thoroughly examining recent research investigations, the paper explains the impact of open-cell metal foams on pool boiling of different liquids such as water, refrigerants, organic liquids, and dielectric liquids. This paper reviews the complexity and various influencing factors involved in flow boiling through metal foam in tubes. It also highlights findings that show metal foam significantly enhances jet impingement boiling heat transfer. Moreover, the discussion on gradient metal foams, offering insights into their potential to enhance boiling heat transfer. The comprehensive review also encompasses numerical modeling studies, such as the lattice Boltzmann method, contributing to a deeper understanding of the intricate flow and heat transfer characteristics within channels filled with metal foam. [ABSTRACT FROM AUTHOR]

The behaviour of non-Newtonian fluids, and their interaction with other fluid phases and components, is of interest in a diverse range of scientific and engineering problems. In the context of the lattice Boltzmann method (LBM), both non-Newtonian rheology and multiphase flows have received significant attention in the literature. This study builds on that work by presenting the development and validation of a phase-field LBM which combines these features in three-dimensional flows. Specifically, the model presented herein combines the simulation of Herschel-Bulkley fluids, which exhibit both a yield stress and power-law dependence on shear rate, interacting with a Newtonian fluid. The developed model is verified and validated using a diverse set of rheological properties and flow conditions, which in their totality represent an additional contribution of this work. Comparison with steady-state layered Poiseuille flow, where one fluid is Newtonian and the other is non-Newtonian, showed excellent correlation with the corresponding analytic solution. Validation against analytic solutions for the rise of a power-law fluid in a capillary tube also showed good correlation, but highlighted some sensitivity to initial conditions and high velocities occurring early in the simulation. A demonstration of the model in a microfluidic junction highlighted how non-Newtonian rheology can alter behaviour from cases where only Newtonian fluids are present. It also showed that significant changes in behaviour can occur when making small and smooth changes in non-Newtonian parameters. To summarise, this work broadens the range of physical phenomena that can be captured in computational analysis of complex fluid flows using the LBM. [ABSTRACT FROM AUTHOR]

Hydrocarbon production in the reservoir depends on fluid flow through its porous media, such as fractures and their physical parameters, which affect the analysis of the reservoir's physical properties. The fracture's physical parameters can be measured conventionally by laboratory analysis or using numerical approaches such as simulations with the Lattice Boltzmann method. However, these methods are time-consuming and resource-intensive; therefore, this research explores the application of machine learning as an alternative method to predict the physical parameters of fractures such as permeability, surface roughness, and mean aperture. Synthetic three-dimensional digital fracture data that resemble real rock fractures were used to train the machine learning models. These included two convolutional neural networks (CNNs) designed and implemented in this research—which are referred to as CNN-1 and CNN-2—as well as three pre-trained models—including DenseNet201, VGG16, and Xception. The models were then evaluated using the R 2 and mean absolute percentage error (MAPE). CNN-2 was the best model for accurately predicting the three fracture physical parameters but experienced a drop in performance when tested on real rock fractures. [ABSTRACT FROM AUTHOR]

The article "Sorting capsules in microfluidic devices" published in the Journal of Fluid Mechanics discusses the use of microfluidic systems for sorting and enriching deformable particle suspensions. The study by Lu et al. explores the interactions between suspended capsules and surrounding fluid in a branched microchannel, providing insights for precise control of microfluidic devices. The research has implications for biotechnology applications and offers guidance for experimental setups. The study's findings can be applied to understand flows of deformable cells in complex geometries and have potential applications in microvascular flows and cancer metastasis research. [Extracted from the article]

The document explores the motion of heavy spheres in a square tube at different Galileo numbers, observing transitions from zigzagging to helical motion. The study also examines the impact of sphere density on motion patterns and vortical structures in the wake. Using a lattice Boltzmann method, the research highlights the influence of sphere-to-fluid density ratio on oscillation periods and drag coefficients for both heavy and light spheres. Additionally, the document contains a collection of research articles focusing on various aspects of sphere motion in fluid environments, providing valuable insights for further research in multiphase flow dynamics. [Extracted from the article]

The article delves into the impact of heater position, mean flow parameters, and flame models on thermoacoustic instability in a Rijke tube through linear stability analysis (LSA) and lattice Boltzmann method (LBM) simulations. Results highlight the LBM's effectiveness in solving intricate thermoacoustic problems, shedding light on the stability range and growth rates of acoustic modes in the Rijke tube. The study also examines the influence of flow and flame parameters on stability, showcasing the intricate dynamics of thermoacoustic systems. The research contributes to a deeper understanding of thermoacoustic phenomena, offering valuable insights for further exploration in this complex field. [Extracted from the article]

This study presents a numerical study of combustion process in a multi-component two-phase flow using the lattice Boltzmann method. The research primarily focuses on the combustion process within liquid propellant rocket engines using monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) as droplets. Building upon our previous work [Latifiyan et al., Acta Mech. 233, 4817–4849 (2022)], which enables concurrent phase transition modeling for both fuel and oxidizer droplets, the droplet combustion and diffusive flame development are simulated using the model of Ashna et al. [Phys. Rev. E 95(5), 053301 (2017)], incorporating temperature-based thermophysical characteristics. The developed biphasic model is verified by simulating n-decane droplet combustion, showing reasonable agreement with experimental data despite minor discrepancies. Additionally, the multi-component model is validated by comparing MMH and NTO droplet combustion with classical numerical results, demonstrating acceptable agreement. The combustion characteristics of the MMH and NTO droplets are explored, followed by investigating the fluctuations in the diffusion flame temperature and fuel evaporation rate by altering the relevant parameters. The results indicate that an increase in the gas phase velocity, NTO droplet diameter, ambient temperature, and reduction in droplet spacing is associated with an elevated flame temperature and a fuel evaporation rate. [ABSTRACT FROM AUTHOR]

Fracture seepage is a critical issue in both engineering and scientific research, yet the role of rough fracture surfaces in driving nonlinear behavior remains poorly understood. This study uses the lattice Boltzmann method to numerically simulate the effects of semicircular rough elements of varying sizes on the flow field, starting from a simplified scenario to explore the nonlinear evolution of rough fractures. The results reveal that rough elements alter both velocity and pressure profiles, with increased velocity above the rough elements and a corresponding pressure drop. Recirculation zones are also formed, growing larger as the rough element radius increases. A relationship was established to describe the interaction between rough elements and fluid, linking the drag coefficient to relative roughness and Reynolds number. Pressure distribution analysis around the rough elements shows that they experience forces primarily in the direction of fluid flow within the channel. By examining non-Darcy flow behavior, a nonlinear seepage model based on the Forchheimer equation was developed for individual rough elements. The findings demonstrate that rough elements are the key factor driving nonlinear seepage changes [ R e ∈ 100 , 160 ]. The complex morphology of the fracture surface leads to variations in velocity and pressure, formation of recirculation zones, and the emergence of nonlinear behavior. [ABSTRACT FROM AUTHOR]

This study explores the impact of the magnetic field on heat transfer and entropy generation in a simulated electronic device using magnetohydrodynamic principles through a three-dimensional hybrid Runge–Kutta and lattice Boltzmann method. By varying Rayleigh number (Ra) from 103 to 106 and Hartmann number (Ha) between 0 and 100, the research evaluated the influence of these parameters on the average Nusselt number (⟨Nu⟩), heat exchange ratio (R), and entropy generation within a confined cavity. The results demonstrated that higher Ra values, particularly for Ra ≥105, significantly enhance convective heat transfer, as reflected by an increase in ⟨Nu⟩. However, introducing a magnetic field (Ha = 50, 100) diminishes this effect by damping fluid motion, resulting in a reduction of ⟨Nu⟩. The heat exchange ratio increases with Ra, reaching a peak value of 0.93 for Ha = 100 and Ra = 105, indicating improved heat dissipation under the magnetic influence. In terms of entropy generation, at low Ra (Ra = 103), thermal conduction is the predominant heat transfer mechanism, with entropy primarily generated due to thermal effects. As Ra increases to 106, the system shifted toward a convection-dominated regime, where entropy generated by viscous effects becomes more significant. Under stronger magnetic fields, particularly at Ha = 100, magnetic entropy generation emerges as a dominant factor, further increasing energy dissipation. These results suggested that magnetic fields can be strategically applied to optimize thermal management in electronic devices by controlling both heat transfer and entropy generation. The effectiveness of this approach, however, is highly dependent on the specific flow conditions and the strength of the applied magnetic field. [ABSTRACT FROM AUTHOR]

Multiblade centrifugal fans are widely used in various fields. With the rapid increase in fan performance requirements, improving aerodynamic performance and reducing noise by modifying individual component parameters are no longer sufficient to meet the demands of actual engineering applications. In this work, a combined noise reduction scheme was adopted to reduce the noise level of the fan under different operating conditions while improving its aerodynamic performance. The three-dimensional unsteady flow and acoustic field of the fan were calculated simultaneously via direct computational aeroacoustics based on the lattice Boltzmann method. Experimental data from the performance test bench and the semianechoic chamber were used to validate the accuracy of the numerical simulation results. A curved-type outlet collector, a nonaxisymmetric inlet nozzle, and a variable inlet/outlet angle blade were designed on the basis of the identified acoustic sources. Different modified schemes provide varying benefits under different operating conditions, but their optimal combination not only reduces the noise of the fan but also improves its aerodynamic performance. The simulation and experimental results show that the total pressure efficiency is significantly improved at the same volume flow rate for both operating conditions and that the noise is reduced by 1.5 and 1.4 dBA. The articulation index improved by a maximum of 5.2%. This study provides a valuable reference for the design of multiblade centrifugal fans with wide operating conditions, high efficiency, and low noise. [ABSTRACT FROM AUTHOR]

Herringbone riblets were regarded as a promising approach to control the separation bubble on the compressor blade. However, the underlying mechanism requires further elucidation. And numerical simulations with body-fitted meshes often face challenges in mesh generation due to the tiny and complex geometries involved. In the present research, high-fidelity simulations using the Lattice Boltzmann Method and Immersed Boundary Method were performed to investigate the effects of herringbone riblets on separated flow in a compressor cascade. At a low Reynolds number of 90 000, a separation bubble appears on the blade suction surface. The application of herringbone riblets on the suction side surface shows that it effectively reduces the bubble length from 0.24c to 0.12c and reduces the loss coefficient by 11%. A counter-rotating mode of secondary flow occurs before the separation, with a near-wall spanwise motion from the divergent region to the convergent region and a compensating flow from the convergent region to the divergent region in the outer layer of the boundary layer. Transition occurs earlier on the suction side surface due to the complex flow patterns. Four different mechanisms are responsible for the earlier transition. Over the divergent region, engulfing of a high momentum fluid from the outer layer to the inner layer of the boundary layer suppresses the separation bubble, forcing a high-momentum passage where an attached boundary layer is observed. This thinner boundary layer leads to an earlier natural transition. Second, the discharge of fluid from the herringbone cusp causes the overflow from the riblet channel beside the divergent line, i.e., overflow transition. Meanwhile, the transition over the converging region is attributed to the accumulation of disturbance. Finally, in the middle region with yawed riblets, transition in a separated shear layer occurs earlier under the influence of adjacent transition mechanisms over the divergent/convergent region. These mechanisms also bring about a serrated structure in the downstream wake. Overall, this research confirms the role of the counter-rotating mode produced by herringbone riblets in separation control and reveals the transition mechanisms for loss production. The findings suggest that proper utilization of herringbone riblets can provide significant improvement on the compressor blade performance. [ABSTRACT FROM AUTHOR]

The flow and heat transfer characteristics around staggered cylinders are critical for optimizing thermal performance in engineering applications like heat exchangers. This study investigates the flow and heat transfer properties around two staggered cylinders at Re = 100 using a double-distributed lattice Boltzmann method. Eight typical flow patterns are recognized based on vortex and temperature fields, phase diagram, and St. The effects of gap flow, shear layer, vortex shedding, and wake evolution behaviors on heat transfer characteristic are discussed. Results demonstrate that when the wake is a single vortex street, the shear layer reattachment and the weaker gap flow both lead to a high temperature in the gap between the two cylinders, which subsequently adversely affects the heat transfer performance. Inversely, the vortex impingement and the stronger gap flow enhance the heat transfer performance. The deflected gap flow leads to a narrow and wide street in the wake, and the cylinder located on the opposite side of the gap flow deflection has better heat transfer performance. Furthermore, two coupled vortex streets in the wake can further improve the heat transfer performance of the cylinders. These findings provide valuable insights for enhancing thermal management strategies in engineering applications. [ABSTRACT FROM AUTHOR]

In this article, two-dimensional numerical simulations are performed to investigate the effectiveness of a hinged splitter plate for manipulating the unsteady laminar wake regime of tandem circular cylinders (TCCs) at a pitch ratio of G/D = 5 and Reynolds number of Re = UD/υ = 100, where G is the distance between the centers of the cylinders having diameter D, U is the free-stream velocity, and υ is the kinematic viscosity of the fluid. These simulations are conducted using the in-house developed flexible forcing immersed boundary-one-step simplified lattice Boltzmann method (FFIB-OSLBM) solver. The splitter plate is hinged to the upstream cylinder's rear base point (HSPU) that pitches at amplitudes θ m (10°–20°) and non-dimensional frequencies S t f (0.1–0.4). The plate length L f / D is varied between 0 and 1. These pitching parameters substantially influence the wake topologies, vortex-interaction modes, pressure distribution, and flow-induced forces on the cylinders. Moreover, the TCC-HSPU combination exhibits four different wake patterns. In Type-I, regular vortex shedding occurs, with the upstream cylinder vortex (UCV) dominating the plate vortex (PV) in the cylinder gap region. The stronger and bigger PV in Type-II forms parallel vortex streets. In Type-III, the PV becomes strong enough to prevent the shedding of UCV. Finally, in Type-IV, the PV attains its maximum strength, and its interaction with UCV forms a new vortex that dominates the cylinder gap region. Among them, Type-II and Type-III regimes are associated with a lower range of drag force on TCC-HSPU configurations. In the considered parametric space, the TCC-HSPU arrangement achieves a maximum drag reduction of 43% compared to the TCC when L f / D = 1.00, S t f = 0.20, and θ m = 15°. [ABSTRACT FROM AUTHOR]

The wake transitions of the flow past two side-by-side elliptical cylinders were numerically investigated using the lattice Boltzmann method at Reynolds numbers (Re) of 40, 100, and 150, with various spacing ratios (L / D , where L represents the distance between the cylinder centers and D is their diameter) and aspect ratios (AR). This study elucidated the effects of Re, AR, and L / D on the flow characteristics, including wake structures, hydrodynamic coefficients, Strouhal number (St), and the spectral energy of the flow exerted on both cylinders. Six distinct flow patterns are observed in the A R − L / D space, such as steady shear layers, anti-phase synchronized streets, in-phase synchronized streets, single bluff body, flip-flopping, and chaotic flow. These patterns were characterized through detailed analyses, including vorticity contour plots, time histories of drag and lift coefficients, power spectral density, and proper orthogonal decomposition of vorticity fluctuations into deterministic spatial structures. Additionally, flow pattern maps and diagrams of the time-averaged pressure coefficients on the surface of the cylinders were provided to assess the influence of Re, AR, and L / D on the flow behavior. The hydrodynamic coefficients of both cylinders showed near-identical trends with significant variations depending on L / D and AR. When AR is small, the time-averaged drag coefficient and the root-mean-squared lift coefficient of both cylinders are found to be substantially higher than those of an isolated elliptical cylinder. Furthermore, a notable increase in the time-averaged lift coefficient was observed when L / D was small, attributed to the repulsive forces between the cylinders. At higher Reynolds numbers (R e = 100 & 150), substantial differences in St emerge, particularly for smaller AR values, despite the cylinders being in a side-by-side configuration. [ABSTRACT FROM AUTHOR]

It is crucially important to understand the dynamics of flash boiling bubbles of liquid fuels in order to achieve optimal fuel spray and mixing performance in realistic combustion engines. In this study, a modified pseudo-potential lattice Boltzmann method was adopted to capture the dynamics of flash boiling bubbles of liquid ammonia. The critical conditions for the flash boiling state of liquid ammonia were determined using isothermal depressurization techniques. Meanwhile, the evolutions of bubble clusters were investigated, allowing for bubble deformation, coalescence, and collapse in different flash boiling stages. The results show that the evolution of flash boiling bubble clusters presents two main stages, i.e., the early rapid expansion stage and the later slow expansion stage, and both stages are highly sensitive to temperature variations. Low-temperature environments can intensify the competition between bubble coalescence and collapse events, thereby changing the density, pressure, and velocity distribution and delaying the transition of bubbles to the eventual equilibrium state. In addition, the evolution of bubble clusters conforms to the Ostwald ripening mechanism, where large bubbles absorb smaller bubbles, promoting the formation and propagation of pressure waves in liquid ammonia. These pressure waves not only disturb the surrounding fluid to form vortices but also cause significant deformation of adjacent bubbles, thereby affecting the overall efficiency of flash boiling processes. [ABSTRACT FROM AUTHOR]

This study investigated the sedimentation of two oscillating cold circular particles within a confined heated channel using the lattice Boltzmann method. The main objective was to investigate the effects of mixed convection, initial particle positioning, and wall confinement on particle behavior under different thermal regimes. In particular, this work sought to explain the mutual interactions between particles in the presence of these effects. Such an investigation is highly significant due to its widespread relevance in various natural and industrial processes involving particle transport. The four-way coupled model was validated against several classical benchmarks, including the drafting-kissing-tumbling interaction. The results demonstrated the critical role of initial particle positioning in promoting oscillatory motion. The reattachment of particle wakes leads to pronounced oscillations and vortex shedding in the trailing particle, especially when the particles are close. While these oscillations enhance the heat transfer coefficient, inter-particle collisions tend to suppress it. The results further revealed a decrease in the average Nusselt number for both particles below two, suggesting potential overestimation in the literature's correlation models. Furthermore, the Magnus force increasingly dominates drag forces as the Grashoff number increases. Notably, the influence of the trailing particle on the leading particle was observed exclusively during particle-wall collisions when close to the leading particle. Overall, this study highlighted the significant impact of thermal forces with wall confinement on particle motion across various thermal regimes, providing valuable insights into complex particle behavior and sedimentation patterns. [ABSTRACT FROM AUTHOR]

Fluid–solid coupling widely exists in some natural phenomena and industrial applications. However, it is still an important challenge to correctly capture the transient changes of particles at fluid interface. We develop a lattice Boltzmann model for particle dynamics at fluid interface, which adopts a coupling strategy by combining the pseudo-force (Shan-Chen) multiphase multicomponent model and the smoothed profile method. In the coupling strategy, a novel extrapolation boundary condition is applied for fluid–solid interface, a repulsive force (bounce-back force) between solid node and fluid node is introduced in the coexistence region (at the fluid–solid interface), to form the interaction between fluid and solid particle. Thanks to the proposed fluid–solid coupling method, the drag force on solid particles can be correctly described, especially for situations of high solid volume fractions. It is found that the wetting angle θ between fluid interface and particle surface is basically linear with the repulsive force coefficient difference ΔG. What is more, to further validate the reliability of our proposed model, we performed two groups of simulations for different Bos = 0.51 (0.84) and 0.83 (1.35), they are the single particle trapped under gravity at deformed fluid interface and the falling single particle impacts fluid interface in the presence of gravity, respectively, and good agreements between simulation results and experimental ones in the description of the relationship between the inertial force and the interfacial tension are obtained, and their correlations are both close to 1, which proves the reliability of our proposed model. [ABSTRACT FROM AUTHOR]

We present a numerical investigation of the coalescence of a drop with a pool of the same liquid. The simulations were carried out with both viscous Newtonian and viscoelastic fluids based on an axisymmetric high density ratio lattice Boltzmann method with a diffuse interface coupled with the Oldroyd-B Model. Particular attention was paid to the widening dynamics of the liquid bridge between the drop and the pool and to the velocity fields within both the drop and liquid bulk. The results were compared with experimental data obtained using a high-speed camera and a micro-particle image velocimetry (μ -PIV) and displayed satisfactory agreement. In particular, the simulated temporary evolution of the rescaled coalescing width of the liquid bridge as a function of the normalized time compares favorably with the experimental results for both the inertially limited viscous and the inertial regimes for short and long time. [ABSTRACT FROM AUTHOR]

We investigate the deformation and breakup behavior of a single droplet in shear and extensional flows, focusing on the effects of the density contrast between the droplet (dispersed phase) and the surrounding matrix fluid (continuous phase). Although many studies have explored the droplet dynamics in such flows, the influence of the density ratio is not yet fully understood. To address this gap, we employ the color-gradient lattice Boltzmann method and perform numerical analysis across a wide range of density ratios and capillary numbers in the Stokes flow regime. We quantify the droplet deformation, elucidate the effects of the density ratio, and carefully analyze the breakup modes, including tip streaming breakup. We confirm that the tip streaming breakup occurs only when the density contrast is large, with values ranging from approximately 1:100 to 1:300 within the test limits. Finally, the flow fields within the droplet are analyzed to elucidate the hydrodynamic origins of these distinct breakup modes. [ABSTRACT FROM AUTHOR]

An improved wettability implementation in the phase-field lattice Boltzmann method for simulating the impact of a droplet onto a cylindrical target is developed. Contact angle control is achieved through a cubic wetting boundary condition that allows precise modeling of wettability. To handle curved surfaces, quadratic interpolation and an image point technique are used to enforce accurate boundary conditions and contact angles. A filtering process is also applied to the phase-field variable to reduce nonphysical artifacts near the interface, ensuring stability and accuracy. The method's validity is demonstrated by simulating droplet impacts on cylindrical surfaces with varying contact angles, from 10° to 170°. Our numerical method provides accurate predictions of the droplet's post-impact phenomena, such as lamella formation, droplet splitting, and film thickness evolution. The numerical results are validated against experimental data and theoretical models, demonstrating good agreement in both qualitative and quantitative aspects. [ABSTRACT FROM AUTHOR]

Oil recovery in shale reservoirs is low due to the dynamics and wettability characteristics in mixed-wet shale oil reservoirs. Nuclear magnetic resonance (NMR) logging, a nondestructive and noninvasive technique, effectively evaluates the continuous dynamics and wettability in these reservoirs. The NMR numerical investigation can characterize the effects of dynamics and wettability, including varying wet regions and wet angles, on NMR responses, providing new insights into the frequency-dependent of T2-based petrophysical parameters. The NMR relaxation theory for mixed-wet shale oil reservoirs was proposed, and the relevant parameters were determined. The dynamics and wettability were characterized using the Shan Chen Lattice Boltzmann method, with constraints based on digital core technology. For the first time, the random walk method was employed to simulate the effects of water-wet regions with varying proportions, echo spacings, and wet angles on NMR responses in mixed-wet shale oil reservoirs at different frequencies. The proportions of water-wet regions, magnetic field frequencies, and echo spacings significantly influence porosity and T2LM, indicating that pore structure governs the dynamics and wettability and that petrophysical parameters can be characterized by their frequency dependence in mixed-wet shale oil reservoirs. [ABSTRACT FROM AUTHOR]

Due to the tightness of shale, its fluid microflow mechanism has always been a hot topic of research. The lattice Boltzmann method has become an effective way to study this mechanism in the gradual improvement over the past few decades. However, current research has not yet provided a unified analysis of various microscale effects and heterogeneity of porous media. By introducing regularization equations, correcting local Knudsen numbers, modifying boundary conditions, and combining with the generalization processing of microscale effects, this article proposes a fully coupled shale gas lattice Boltzmann model that includes all the above-mentioned factors. The simulation results show that the microscale effects will have a significant impact on gas flow when the pore diameter is below 10 nm. When the pore size is greater than 50 nm and the pressure is greater than 20 MPa, the influence of Knudsen diffusion can be ignored. Compared to Knudsen diffusion, surface diffusion requires lower pressure and smaller pores to manifest. The surface diffusion rate will reach its optimal state at a pore size of 5 nm and a pressure of 10–20 MPa. The impact of surface diffusion can be ignored when the pore size is larger than 20 nm. [ABSTRACT FROM AUTHOR]

In this study the computational analysis of the flow topology around two rectangular cylinders is performed using the lattice Boltzmann method. The cylinders are arranged in a staggered configuration, and both share the same aspect ratio. For simulations, the Reynolds number is kept constant at 150 while the gap spacing, between the cylinders, is varied within the range from 0 to 10 times the width of the cylinders. Four different flow patterns observed in this study are the isolated bluff structure, chaotic flow, modulated synchronized flow, and synchronized flow. The observed flow patterns and the corresponding fluid force parameters such as average drag coefficient, root-mean-square of the drag and lift coefficient, the amplitude of drag and lift, as well as the Strouhal number, are found to be strongly influenced by the gap spacing between cylinders. At low gap spacing values, a robust effect of jet flow disturbs the flow structure, which ultimately results in a complex flow structure in the wake and random fluctuations in drag and lift forces. With an increase in spacing values, the effect of jet flow on fluid flow characteristics gradually minimized, which results in a smooth periodic flow in the wake of both cylinders. [ABSTRACT FROM AUTHOR]

This study examines the variations in wake structures and fluid forces around a cluster of five square cylinders. The cylinders in the cluster are arranged such that a larger cylinder (the main cylinder) is surrounded by four similar but small-sized cylinders, which are very common in marine risers and axial pipe shrouds. The analysis uses an in-house developed code based on the lattice Boltzmann method. The gap spacing (g*) between the main and the surrounding cylinders varies from 0 to 10 while maintaining a fixed Reynolds number (Re) of 200. The accuracy and consistency of the code are first tested through simulations that examine the flow behind a single cylinder, revealing strong concurrence with the existing data. In the next step, the flow characteristics of the pentad arrangement are analyzed. Five diverse flow modes, including the extended single bluff body flow, stable symmetric flow, chaotic irregular shedding, antiphase symmetric flow, and modulated periodic flow, are observed depending on the gap distances. It is found that the small cylinders in the downstream position from the primary cylinder experience a negative mean drag at narrow gaps. In contrast, those at the upstream position are subjected to a positive drag force regardless of the gap spacing. The main cylinder has a higher drag coefficient compared to other cylinders for all gap spacing cases. The shedding frequencies appear similar for upstream and downstream smaller-size cylinders at higher spacing values, while the shedding frequencies for the main cylinder significantly deviate from the surrounding small cylinders. [ABSTRACT FROM AUTHOR]

In polymer electrolyte membrane fuel cells, the gas diffusion layer (GDL) is composed of porous media and serves a critical role as a mass transport layer, facilitating reactant gas diffusion, removal of water generated in the catalyst layer, and electron transport. Artificial spacings known as perforations can be introduced to improve water management within this mass transport system. However, the impact of these perforations on the effective electrical conductivity has not been adequately studied. This study employs numerical methods to investigate water management and effective electrical conductivity in the presence of perforations, aiming to provide indicators for optimal design. The pseudopotential lattice Boltzmann method is utilized, which is particularly advantageous for modeling two-phase flow and electron transport in complex geometries. Using this numerical approach, we analyze water penetration in GDL structures and effective electrical conductivity based on electric potential fields focusing on geometric parameters such as the perforation size. Our results demonstrate a relationship between water management efficiency and effective electrical conductivity, suggesting the existence of an optimal perforation diameter. Moreover, when there is a water-induced penetration pattern due to the perforated structure, both the effective electrical conductivity and water management are enhanced at a lower porosity of the GDL structure. [ABSTRACT FROM AUTHOR]

The low-resolution CT scan images obtained from drill core generally struggle with problems such as insufficient pore structure information and incomplete image details. Consequently, predicting the permeability of heterogeneous reservoir cores relies heavily on high-resolution CT scanning images. However, this approach requires a considerable amount of data and is associated with high costs. To solve this problem, a method for predicting core permeability based on deep learning using CT scan images with different resolutions is proposed in this work. First, the high-resolution CT scans are preprocessed and then cubic subsets are extracted. The permeability of each subset is estimated using the Lattice Boltzmann Method (LBM) and forms the training set for the convolutional neural network (CNN) model. Subsequently, the high-resolution images are downsampled to obtain the low-resolution grayscale images. In the comparative analysis of the porosities of different low-resolution images, the low-resolution image with a resolution of 10% of the original image is considered as the test set in this paper. It is found that the permeabilities predicted from the low-resolution images are in good agreement with the values calculated by the LBM. In addition, the test data are compared with the results of the Kozeny-Carman (KC) model and the measured permeability of the whole sample. The results show that the prediction of the permeability of tight carbonate rock based on deep learning using CT scans with different resolutions is reliable. [ABSTRACT FROM AUTHOR]

The paper is devoted to the parametric stability optimization of explicit Runge–Kutta methods with higher-order derivatives. The key feature of these methods is the dependence of the coefficients of their stability polynomials on free parameters. Thus, the integral characteristics of stability domains can be considered as functions of free parameters. The optimization is based on the numerical maximization of the area of the stability domain and the length of the stability interval. Runge–Kutta methods with higher-order derivatives, presented in previous works, are optimized. The optimal values of parameters are computed for methods of fourth, fifth, and sixth orders. In numerical experiments, optimal parameter values are used for the construction of high-order schemes for the method of lines for problems with partial differential equations. Problems for linear and nonlinear hyperbolic and parabolic equations are considered. Additionally, an optimized scheme is used in lattice Boltzmann simulations of gas flow. As the main result of computations and comparison with existing methods, it is demonstrated that optimized schemes have better stability properties and can be used in practice. [ABSTRACT FROM AUTHOR]

The hydraulic fracturing process is a prominent example of fracture network evolution under stress. However, the interactions between hydraulic fractures and natural fracture networks, along with the connectivity evolution of the resultant fracture networks, require more research. This research incorporates discrete fracture networks to characterize subsurface structures and employs the Discrete Element ‐ Lattice Boltzmann Method to simulate the hydraulic fracturing process. The dynamic evolution of subsurface structures, including the initiation of hydraulic fractures and their interaction with natural fractures, is systematically investigated. Results indicate that natural fractures significantly impact fracture initiation, propagation, and connectivity evolution, which in turn affects fluid production. Fracture strength is key for the interaction, and hydraulic fractures tend to propagate along weak natural fractures with low resistance. Fracture strength variability determines the final fracture networks, with low‐strength fractures breaking due to the altered in‐situ stress and forming local clusters. High injection rates and fluid viscosity result in a large pressure buildup and exaggerate the influential region. A multi‐cluster system is thus formed during the hydraulic fracturing process, and its connectivity can be well quantified with a novel connectivity metric. In low‐permeable reservoirs, fracture clusters connected to production wells can contribute instantly, while local clusters may contribute to production from a long‐term perspective. Injection rate, fluid viscosity, fracture orientation, and clustering effects have consistent positive correlations with the total connectivity and production. Heterogeneity has a weak positive correlation with fluid production, while a moderate negative correlation with total connectivity. Plain Language Summary: Hydraulic fracturing is a widely employed technique in developing unconventional reservoirs. Ubiquitous natural fractures in the deep subsurface significantly influence the hydraulic fracturing outcomes; however, the interactions between hydraulic and natural fractures remain incompletely understood. In this work, we optimize the numerical scheme to incorporate natural fractures and explore their impact on hydraulic fracturing. We found that natural fractures significantly impact fracture initiation, propagation, and connectivity evolution, which in turn affects fluid production. Fracture strength is key for the interaction, and hydraulic fractures tend to propagate along weak natural fractures with low resistance. Fracture strength variability can significantly impact the final fracture networks. Low‐strength fractures tend to break due to the altered in‐situ stress, forming local clusters. High injection rates and fluid viscosity result in a large pressure buildup and exaggerate the influential region. Furthermore, we propose a connectivity metric to quantify the connectivity evolution of multi‐cluster fracture networks formed during the hydraulic fracturing process. Therefore, the quantitative analysis of sensitivity for influential factors on connectivity and production is available and discussed. These findings are essential for us to better understand the subsurface structures and their dynamic evolution under the hydraulic fracturing process. Key Points: Natural fractures significantly impact fracture initiation, propagation, and connectivity evolution during hydraulic fracturingLow‐strength fractures break due to altered in‐situ stress, resulting in the final fracture networks forming a multi‐cluster systemHeterogeneity is crucial in forming final fracture networks, and high injection rates and viscosity exacerbate their influence areas [ABSTRACT FROM AUTHOR]

Many interesting particulate flow problems can only be studied using efficient numerical methods. We present a method based on a lattice Boltzmann fluid coupled to unresolved particles that interact with each other via the Discrete Element Method. Our method improves upon existing numerical schemes through the addition of a novel subcycling algorithm that guarantees momentum conservation during each DEM substep. The intended application is studying transport of solid particles in physiologic processes, although the method is generally applicable. We present in detail the development and (parallel) implementation of the model and show how intricacies of the coupling scheme must be considered to avoid unphysical behavior and instabilities. The scalability of the code is tested on two modern supercomputers. We demonstrate the method's applicability to biomedical applications by simulating the injection and distribution of particles in an idealized liver vasculature.   • 4-way coupled unresolved LBM-DEM method to simulate particulate flows. • Thorough discussion of the method's parallel implementation. • Novel subcycling scheme that guarantees momentum conservation at each DEM substep. • Scaling tests on two modern supercomputers up to 8192 CPU cores. • Application of the method to falling particle clouds and liver radioembolization. [ABSTRACT FROM AUTHOR]

In recent years, Lattice Boltzmann (LB) schemes have been adapted to the simulation of elastodynamics. The resulting methods show promising characteristics, especially the computational efficiency and the scaling to large systems. A constitutive model is needed for solids, which is captured by a source term in the LB formulation. However, this approach leads to problems with the numerical stability for a large regime of material parameters. In this publication, a linear elastic material model is regarded. This work regards the underlying reasons for instabilities. As a remedy, a two‐relaxation‐time collision operator is employed. Effects on the stability are examined through error measures of a dynamical simulation model. [ABSTRACT FROM AUTHOR]

The variable coefficient nonlinear Schrödinger equation has a wide range of applications in various research fields. This work focuses on the wave propagation based on the variable coefficient nonlinear Schrödinger equation and the variable coefficient fractional order nonlinear Schrödinger equation. Due to the great challenge of accurately solving such problems, this work considers numerical simulation research on this type of problem. We innovatively consider using a mesoscopic numerical method, the lattice Boltzmann method, to study this type of problem, constructing lattice Boltzmann models for these two types of equations, and conducting numerical simulations of wave propagation. Error analysis was conducted on the model, and the convergence of the model was numerical validated. By comparing it with other classic schemes, the effectiveness of the model has been verified. The results indicate that lattice Boltzmann method has demonstrated advantages in both computational accuracy and time consumption. This study has positive significance for the fields of applied mathematics, nonlinear optics, and computational fluid dynamics. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the three-dimensional dynamics of droplet impact on a thin liquid substrate using the lattice Boltzmann method (LBM). The LBM solver is employed to simulate the fluid dynamics of the droplet-substrate interaction and the subsequent formation of waves on the substrate surface. The study specifically focuses on the influence of Weber number on the collision dynamics between the droplet and substrate, as well as the resulting wave patterns. The simulation results provide insights into the behaviour of the droplet-substrate interface, including the formation of a 'neck' region and the fluid recirculation around it. Moreover, the study examines the impact of Weber's number on the amplitude and frequency of the resulting waves. This research holds significant implications for applications in microfluidic and microelectromechanical systems (MEMS*), where a thorough understanding of droplet impact dynamics is crucial for the design and optimisation of inkjet print heads and other droplet-based systems. By offering an in-depth understanding of the droplet-substrate interaction, this study contributes to the development of more efficient and precise droplet production systems. [ABSTRACT FROM AUTHOR]

The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio (ε), squirmer-type factor (β) and blockage ratio (κ) on swimming efficiency (η) and power expenditure (P). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., κ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when ε ≤ 3. Notably, squirmer rods with a larger aspect ratio ε and a β value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when ε > 4 and β = ±1, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment. [ABSTRACT FROM AUTHOR]

The study is focused on the use of nanofluids in a micro-open tall cavity, which is a type of micro heat exchanger (MHE). The cavity is heated from the bottom sidewall in a sinusoidal pattern, and the effects of four input parameters (Ra, Ha, Kn, and Vf) on heat transfer and irreversibility are investigated using numerical simulations based on Lattice Boltzmann Method (LBM). The findings of the study suggest that the local heat transfer on the bottom sidewall is strongly influenced by Ra and Ha, while the surface distribution of entropy generation is mainly dependent on Kn. The study also shows that the optimization of the magnitude and wavelength of the sinusoidal temperature can improve both local heat transfer and surface distribution of entropy generation. The results of the study provide valuable insights into the design of micro heat exchangers and suggest that the optimization of micro-porous geometries using DOE could lead to increased energy efficiency. The study contributes to our understanding of the complex interactions between input parameters in micro heat exchangers and highlights the importance of considering multiple parameters in the design process. [ABSTRACT FROM AUTHOR]

The homogenized lattice Boltzmann method (HLBM) has emerged as a flexible computational framework for studying particulate flows, providing a monolithic approach to modeling pure fluid flows and flows through porous media, including moving solid and porous particles, within a unified framework. This paper presents a thorough review of HLBM, elucidating its underlying principles and highlighting its diverse applications to particle-laden flows in various fields as reported in literature. These include studies leading to new fundamental knowledge on the settling of single arbitrarily shaped particles as well as application-oriented research on wall-flow filters, hindered settling, and evaluation of the damage potential during particle transport. Among the strengths of HLBM are its monolithic approach, which allows seamless simulation of different fluid-solid interactions, and its ability to handle arbitrary particle shapes, including irregular and concave geometries, while resolving surface interactions to capture local forces. In addition, its parallel scheme based on the lattice Boltzmann method (LBM) results in high computational efficiency, making it suitable for large-scale simulations, even though LBM requires small time steps. Important future development needs are identified, including the addition of a lubrication force correction model, performance enhancements, such as support for hybrid parallelization and GPU, and the extension of compatible contact models to accommodate concave shapes. These advances promise expanded capabilities for HLBM and broader applicability for solving complex real-world problems. [ABSTRACT FROM AUTHOR]

The objective of this work is to examine the unexplored dynamics of flow regime changes in linear channels, with a specific emphasis on the impact of relaxation time, channel width, and external forces on the shift from laminar to turbulent flow. This study intends to improve understanding of how the parameters associated with the Lattice Boltzmann model for shallow water equations (LABSWE) can be modified to change flow regimes using a D2Q9 approach for domain discretization. Our investigations demonstrate that a decrease in relaxation time prompts a shift from a parabolic (laminar) to a logarithmic (turbulent) velocity distribution, evidenced by significant fluctuations in the central channel velocity and an increase in the Reynolds number. This study also reveals that broader channel widths lead to turbulent flow, marking a notable departure from the laminar flow observed in narrower settings. The application of external forces further intensifies this transition, showcasing their pivotal role in influencing flow regimes. This study presents significant scientific novelty by offering new insights into the conditions that foster flow regime transitions, thereby addressing a gap in the current fluid mechanics literature. Our findings suggest practical ways to manipulate these factors to optimize flow behaviors, providing valuable insights for the engineering and environmental management of water systems. [ABSTRACT FROM AUTHOR]

This paper presents the development of a quasi-three-dimensional model that utilizes an equilibrium technique to investigate the morphological change of a channel focused on transport of sediment. The authors developed a computational algorithm that integrates two numerical techniques, specifically the Lattice Boltzmann Method (LBM) and the finite-difference method (FDM), to perform a hybrid calculation. The aforementioned algorithm was employed to investigate the impact of dykes on the dynamics of channel flow, sediment transport, and bed evolution. To derive the three-dimensional velocity field, the Boltzmann lattice method is employed to compute the two horizontal components of the vertically integrated velocity. Subsequently, these two components are combined with a logarithmic vertical profile. The process of sediment particle transport can be divided into two components: the bed load transport rate and the suspended load transport rate. The latter determination is achieved through the computation of the equilibrium flow rate of suspended sediment, which is derived from the equilibrium concentrations and logarithmic velocities. by comparing its outputs to previous research on constant width channels and horizontal beds, especially in dykes, the model was validated. This model accurately predicts sediment transport as bed load and suspended load, which is important for understanding sediment dynamics around such structures. the model's ability to anticipate sediment erosion and deposition across the channel, providing crucial insights into river detours and other sedimentary processes. [ABSTRACT FROM AUTHOR]