Mesoscopic Method Research Articles

The influence of particle density and diameter on the interactions between the finite-size particles and the turbulent channel flow

Understanding the influence of different particle parameters on the two-way interactions between the particles and wall-bounded turbulence is important in many natural phenomena and engineering applications. In this work, particle-resolved direct simulation of particle-laden turbulent channel flow is performed based on the mesoscopic lattice Boltzmann method (LBM), and the particle–fluid interface is treated using the interpolated bounce back scheme. The friction Reynolds number (Reτ) of the single phase turbulent channel flow is 180, and the particle volume fraction is fixed at 1%. Three particle–fluid density ratios and three particle diameters are considered, and five particle-laden simulations are performed to investigate the influence of particle density and diameter on the interactions between the particles and the carrier turbulence. Results show that the streamwise velocity of the solid phase is larger than that of the fluid phase in the near-wall region, and the velocity difference between the two phases decreases with increasing particle density, but increases with increasing particle diameter. The probability density functions (PDFs) of particle velocity and angular velocity depend on the distance between the particles and the wall, but the PDFs of particle acceleration and angular acceleration are not spatially dependent. The distribution of particle Reynolds number follows the Gamma distribution within the buffer region and viscous sublayer. The solid phase concentration is high in the near-wall region, and the largest solid-phase concentration in this region occurs in the case with particles of intermediate density. Particles with different parameters would lead to different modulation to the carrier flow. Then, two aspects of the turbulence modulation are explored, i.e., the streamwise velocity and the turbulent kinetic energy (TKE). The presence of finite-size particles typically increases the streamwise velocity in the near-wall region and reduce the streamwise velocity outside this region. The trend is similar for TKE, but the TKE attenuation mainly occurs in the buffer region. The modulation to the streamwise velocity is analyzed using the streamwise momentum balance equation. It is found that the streamwise velocity modulation is dominated by the weighted Reynolds stress, but the different modulation in the near-wall region is due to the difference in weighted particle-induced stress, whereas the different modulation outside the near-wall region is due to the change in weighted Reynolds stress. Through TKE budget analysis, it is found that the enhancement of the total TKE source in the viscous sublayer increases with increasing particle density and diameter and the attenuation of total TKE source in the buffer region increases with increasing particle density and diameter, which is consistent with the TKE modulation for different cases.

Heat flux from the surface in the process of the rupture of a thin liquid film by an electric field

In this article, the cooling of a solid surface by an evaporating film of a dielectric liquid and the influence of an electric field on this process are studied. The mesoscopic lattice Boltzmann method is applied to simulate the fluid flow with phase transitions and the heat transfer. The cases without electric field, with initially uniform electric displacement field, and with non-uniform electric field are considered. A uniform field enhances the cooling slightly. Non-uniform field leads to the rupture of the film. In this case, the local heat flux in local regions increases significantly when the film becomes thin and effectively evaporates. After the rupture of the film, the heat flux from a dry spot decreases abruptly. The formation of a dry spot can be prevented by switching off the electric field before the film rupture. Thus, we demonstrate the possibility of enhanced cooling of local regions at a surface using pulses of non-uniform electric field acting on a thin film of dielectric liquid placed at the surface. If the inflow of liquid to the film could be provided, it is in principle possible to realize a periodic process of application of voltage pulses to electrodes and to enhance the cooling of surface by the evaporation of a film of dielectric liquid.

Effect of specularity parameter and convective coefficient on heat transport in semiconductor devices based on mesoscopic method

The effects of thermal behavior on nanoscale Metal Oxide Semiconductor Field Effect Transistor (nano-MOSFET) are still being studied by the semiconductor industry. This study investigates the heat diffusion inside double-gate (DG) and nano-conventional MOSFETs. Simulations of conventional and DG MOSFET are carried out using mesoscopic model lattice Boltzmann method (LBM) coupled with specularity parameter and convective heat transfer coefficient. The simulation results show that the specularity parameter and convective heat transfer term have important role to reduce hotspots in nano-devices. Temperature decreases when the specularity parameter and convective term increase. The temperature reaches 326.76 K for p = 0.1 while for p = 0.4 estimated 320.79 K at the same Rth−1=1010 W/(m2⋅K) in traditional device at t = 30 ps whereas the temperature in the double gate transistors reached 326.28 K and 321.48 K for p = 0.4 and 0.8, respectively. In addition, it is found that the conventional device compared with the double gate device is more heat stability.

Toward a Mesoscopic Modeling Approach of Magnetohydrodynamic Blood Flow in Pathological Vessels: A Comprehensive Review.

The investigation of magnetohydrodynamic (MHD) blood flow within configurations that are pertinent to the human anatomy holds significant importance in the realm of scientific inquiry because of its practical implications within the medical field. This article presents an exhaustive appraisal of the diverse applications of magnetohydrodynamics and their computational modeling in biological contexts. These applications are classified into two categories: simple flow and pulsatile flow. An alternative approach of traditional CFD methods called Lattice Boltzmann Method (LBM), a mesoscopic method based on kinetic theory, is introduced to solve complex problems, such as hemodynamics. The results show that the flow velocity reduces considerably by increasing the magnetic field intensity, and the flow separation area is minimized by the increase of magnetic field strength. The LBM with BGK collision model has shown good results in terms of precision. Finally, this literature review has revealed a number of potential avenues for further research. Suggestions for future works are proposed accordingly.

Hybrid simulation of dissipative particle dynamics and computational fluid dynamics for friction drag reduction of polymer coatings

Frictional drag reduction (DR) can lead to substantial fuel savings in marine vehicle propulsion. The application of polymer coatings on vehicle surfaces has been found to assist in reducing drag. However, there has been limited investigation into such non-uniform polymer drag reduction in external flows. This study proposes a novel numerical model that combines a mesoscopic method with computational fluid dynamics (CFD) techniques. The CFD portion of the model uses direct numerical simulation (DNS) and large eddy simulation (LES) methods, which are verified against reference data. Firstly, the mesoscopic dissipative particle dynamics (DPD) method is coupled with DNS and LES methods, and the finitely extensible nonlinear elastic approach is used to validate the results obtained using this DNS/LES-DPD method. The performance of the model is evaluated at three representative Reynolds numbers (180, 395, and 590) to confirm its universal applicability. The model is then used to investigate the influence of the height of the polymer region on non-uniform polymer DR. Notably, the LES method offers computational savings when the Reynolds numbers are high. The model also reveals that the polymer DR efficiency is significant even when the polymer region does not extend across the entire fluid area such as the application of polymer coating. This model represents a foundation for further research on polymer coatings DR and energy conservation of vessels.

Combined immersed boundary and discrete unified gas kinetic scheme for the motion of an autonomous underwater vehicle model with slip over a solid-liquid interface

To improve the endurance and speed of an autonomous underwater vehicle (AUV), we consider adopting the slip over a solid-liquid interface, which has the effect of drag reduction. However, the simulation of motion of an AUV with the slip remains a challenge due to the fluid-structure interaction and multiscale problems involving the moving boundary. To solve these problems, the present work proposes a novel and competitive mesoscopic method. Firstly, the Discrete Unified Gas Kinetic Scheme (DUGKS) coupled with the immersed boundary method is improved by correcting the boundary force, avoiding any additional computational time or implementation effort. Its effectiveness and accuracy are validated by two numerical tests involving the moving boundary. Furthermore, a fluid-solid interaction force is introduced to this method to model the slip condition due to its easy and effective implementation. We perform the experiment of motion of an AUV model in water to further validate the proposed method, which shows that it can predict acceptable results. Then, the method is applied to study the effect of the slip on the motion of the AUV model. The greater slip induced by the fluid-solid interaction force has a greater effect on reducing the drag and improving the velocity. It is indicated that increasing the fluid-solid interaction force can increase the amplitude and decrease the oscillation frequency of the drag curve. Overall, the slip can improve the endurance and speed of the AUV model.

Mesoscopic numerical study of the startup characteristics of grooved heat pipe under high heat flux

The dry-out phenomenon that occurs in the evaporation section under high thermal load can lead to heat pipe startup failure, which considerably affects the safe and efficient operation of microelectromechanical systems. In this study, the startup characteristics of a grooved heat pipe are investigated with the mesoscopic lattice Boltzmann method. The focus is on the effects of wettability, inclination angle, and liquid filling volume on the evolution of the liquid supply velocity and dry-spot area. Results show that nucleate boiling can be formed by starting the heat pipe at high heat flux, and the vapor jetting generated by bubble bursting can reduce the liquid supply velocity by more than 70%. Capillary pressure can be increased, and the perturbation of bubbles to the meniscus region can be suppressed by enhancing the wettability of the capillary wick, thus promoting the return of the condensate to the evaporation section. The pressure on the liquid side in the evaporation section decreases as the inclination angle increases, which shortens the waiting time for vapor core formation and improves the stability of boiling behavior. A non-monotonic relationship exists between the liquid filling volume and heat transfer limit time of the heat pipe, which reaches the maximum only when the initial liquid layer fills the capillary wick exactly.

Relationship analysis of surface roughness measurements on coatings using AFM and fractal dimension by mesoscopic model methods

Surface coating is a method used for protection against corrosion and environmental impact for metals. In the case of solid surfaces, coatings can be achieved by radio-frequency magnetron sputtering or other corrosion-resistant substances, which may involve the deposition of one or more layers, depending on the procedure involved, modifying the morphology of the surface and surface area. This work aims to study the relationship of two surface morphological methods through roughness and fractal dimension measurements in top-surface coatings, bilayer Ti/WTiN/WTiC (named as n = 1); multilayer [Ti/WTiN/WTiC] (named as n = 40) deposited by RF-magnetron sputtering. The measurements were obtained by profilometer and image processing pixel intensity. The topography of each coating exhibited texture with impurities as domes distributed in small cluster island types. The surface roughness were 9.42 and 18.63 nm; fractal dimension measurements were 2.55 and 2.32, respectively, with a low correlation between roughness and fractal dimension. The R-squared analysis exhibited a good relationship between the fractal dimension values, tending linear regression negative. The result of factorial design 22 confirmed the performance correlation and linear regression analyses. The fractal dimension measurements by the optical method can be great potential to evaluate surface roughness complementary in applications such as laboratories and even in scale industrial. Thus the result of statistical treatment shows high accuracy in the measurements.

Coarse-grained simulations of lysozyme-silica-nanoparticle corona.

Protein coronas, formed by proteins and nanomaterials, have various applications in the biomedical field. Here, large-scale simulations of protein coronas have been carried out by an efficient mesoscopic coarse-grained method with the BMW-MARTINI force field. The effects of protein concentration, size of silica nanoparticles (SNPs), and ionic strength on the formation of lysozyme-SNP coronas are investigated at the microsecond time scale. Simulations results indicate that (i) an increase in the amount of lysozyme is favorable for the conformation stability of adsorbed lysozyme on SNPs. Moreover, the formation of ringlike and dumbbell-like aggregations of lysozyme can further reduce the conformational loss of lysozyme; (ii) for a smaller SNP, the increase of protein concentration exhibits a greater effect on the adsorption orientation of lysozyme. The dumbbell-like lysozyme aggregation is unfavorable for the stability of lysozyme's adsorption orientation; however, the ringlike lysozyme aggregation can enhance the orientation stability; (iii) the increase of ionic strength can reduce the conformation change of lysozyme and accelerate the aggregation of lysozyme during their adsorption process on SNPs. This work provides some insights into the formation of protein coronas and some valuable guidelines for the development of novel biomolecule-NP conjugates.

Numerical study of pulsatile thermal magnetohydrodynamic blood flow in an artery with aneurysm using lattice Boltzmann method (LBM)

Aneurysm is considered as one of the most common cardiovascular diseases with an important mortality rate. It is a serious pathology caused by a dilatation in the arterial wall. In this work, the influence of magnetic field on pulsatile blood flow and heat transfer in an artery with aneurysm is studied using the mesoscopic lattice Boltzmann method with BGK approximation (LBGK). Human blood is regarded as non-Newtonian and modeled by Carreau–Yasuda rheological model. The model findings are compared with recent data from the literature and demonstrate a good level of agreement, which confirms the effectiveness and accuracy of the suggested model. Results are depicted in terms of streamlines, temperature contours and wall shear stress (WSS) variation, for the certain pertinent non-dimensional Reynolds and Hartmann numbers. The findings demonstrate that the heat transfer is enhanced in the inlet zone of the aneurysm as the Hartmann number increases. Furthermore, it is found that the application of a magnetic field reduces the recirculation zones and increase the WSS, which prevent the progression of vascular diseases and rupture in the aneurysm region.

Analyzing the Impact of Strategies for Separating Trucks and Cars: IH 20 Truck-Only Lane Case Study

This research examined the use of truck-only lanes to separate truck freight traffic from general passenger traffic along the 32-mi interstate highway (IH) 20 corridor between Dallas and Fort Worth, TX, United States. The corridor was selected because of its high truck percentage, locations of complex weaving and interactions between trucks and automobiles, and grade change issues that affect truck performance and raise safety concerns. The simulation-based modeling approach leveraged both mesoscopic and microscopic modeling methods. Dynamic traffic assignment (DTA)-based multiresolution modeling examined the regional impact of adding truck-only lanes along the entire IH 20 study corridor, whereas microsimulation focused on a specific segment with distinct operational challenges to model the interaction between truck traffic and general passenger traffic. The DTA mesoscopic model for the region predicted that around 3,000 trucks daily might shift to the dedicated truck-only lanes in both directions giving a travel time saving of 12% in each direction compared with the base case (no build). Focusing on the microsimulation case study to add an inside truck-only climbing lane on a 5-mi segment on IH 20, the model predicted an average increase in speed of 11 mph for eastbound traffic during the morning peak-hour but limited travel time benefits during the morning and afternoon peak hours in either direction. Reasonable safety and operational benefits were observed based on the analysis.

Three-dimensional mesoscopic simulation of radiative transfer in graded index media

Light propagation in three-dimensional (3D) graded index (GRIN) media has a complex spatial path, making it difficult to solve thermal radiative transfer problems. In this paper, a mesoscopic lattice Boltzmann method (LBM) that implements simple steady-state and transient radiative transfer solutions in 3D GRIN media is proposed. During the construction of the lattice Boltzmann (LB) model, the concept of the “local radiative transfer direction”, which addresses complex curved trajectories in 3D GRIN media simply, is introduced. The radiative transfer equation of 3D GRIN media can be strictly recovered from the LB model by adopting the Chapman-Enskog analysis. Numerical results indicate that radiative transfer problems in 3D GRIN media can be solved effectively by the LBM. Additionally, the influences of different optical parameters on steady-state and transient radiative transfer in 3D GRIN media are discussed. The LBM is a promising mathematical tool for radiative transfer in 3D GRIN media.

Shear failure of geometrically similar RC shear walls: Mesoscopic modellings and analysis

Reinforced concrete (RC) shear wall often exhibits a brittle failure pattern, which may present an obvious size effect. The objective of this study is to explore the size effect on RC shear walls with shear failure. The failure of RC shear walls having different structural sizes and aspect ratio of 1.0 was simulated by a two-dimensional mesoscopic simulated method. In 2D simulation, the concrete heterogeneities and concrete/steel interactions were explicitly considered. The mesoscopic simulation method was first verified with the available experiment observations, and was utilized to study the influences of axial load ratio and horizontal reinforcement ratio on the failure of RC shear walls having different structural sizes. The results indicate that: 1) the simulated RC shear walls present brittle failure patterns, exhibiting obvious size effect; 2) the increase of horizontal reinforcement ratio improves the shear bearing capacity of shear walls, while it would weaken or even suppress the size effect on nominal shear strength; and 3) the increasing axial load ratios improve the shear bearing capacity and lead to a stronger size effect. Moreover, a novel size effect law was proposed considering the quantitative effects from horizontal reinforcement ratios and axial load ratios for size effect.

A mesoscopic numerical method for fracture energy of concrete

AbstractThis paper develops a mesoscopic numerical method for evaluating the fracture energy of concrete. In this method, concrete is modeled as a three‐phase composite material, composed of mortar, coarse aggregate, and the interface between them. The actual mixed‐mode I–II crack growth path in mode I fracture tests is traced by applying crack propagation criteria. After verifying the numerical method by a series of three‐point bending tests, the effects of aggregate location, aggregate size, and crack propagation path on the fracture energy of concrete are evaluated. It is found that for the fracture mode of crack bypassing aggregates, the actual fracture energy of concrete is significantly affected by the aggregate location but independent of the aggregate size and the crack propagation path.

Size effect on the FPZ length in notched beams: Mesoscopic method and theoretical analytical

A microscopic finite element model of three-point bending (TPB) notched lightweight concrete beams is established in this paper. The behavior of discrete crack initiation and propagation in notched beams is simulated based on the cohesive and interface frictional coupling model. The correctness of the microscopic model is verified by the experimental data from related literature, and the length evolution of the fracture process zone (FPZ) during the loading process of the microscopic notched beams is performed. Meanwhile, the evolution laws of macroscopic and mesoscopic characteristic parameters such as the crack-height ratio, porosity, lightweight aggregate strength, and the lightweight aggregate volume fraction on the FPZ length of the mesoscopic notched beams are studied. In addition, the size effect of the FPZ of the mesoscopic notched beams is analyzed. The size effect law based on the critical distance line criterion is derived and the effect of high-order terms of the stress field is considered. The functional relationship between the nominal strength, FPZ length, and notched beam height is obtained to explain the size effect phenomenon. The results show that the FPZ length obtained by the mesoscopic method is in good agreement with the FPZ length obtained by the critical distance line criterion.

Phase-field study of the effect of stress field and fission rate on intragranular Xe bubble evolution in U3Si2 nuclear fuel

Due to the superior thermal conductivity and high uranium density, U3Si2 is an excellent candidate for conventional UO2 nuclear fuel and shows great potential application in accident-tolerant fuel (ATF) assembly of light water reactors (LWRs). Currently, the behavior of Xe bubbles with internal or applied stress is rarely investigated, restricting further understanding of swelling in U3Si2. The mesoscopic phase-field method has been developed in this work to study the spatial and temporal Xe bubble evolution in U3Si2. The results show that the bubble density and its average size increase as the fission rate increases. Applied stress accelerates the nucleation and growth of gas bubbles, reshaping the bubbles’ morphology from spherical in a stress-free state into elongated along the applied direction in a stressed state. The gas bubbles in a local dislocation stress field nucleate preferentially at stress-concentrated sites and spread over the whole system in succession, and the bubble coarsening is controlled by the stress overlap of the dislocation pair. The results show a practical phase-field method for Xe bubble evolution study in U3Si2, which can be expanded into swelling behavior investigation in other fuels and lay a solid foundation for the development of ATF assembly.

Study of low-level pool boiling in vapor chamber of wickless micro-heat pipe based on Lattice Boltzmann pseudopotential method—Effects of superheat and wall wettability

The lattice Boltzmann method, a mesoscopic numerical method with a solid kinetic basis, is used to establish a low-level pool boiling model to exhibit the transport phenomena inside an evaporation chamber of a wickless micro heat pipe using DI water as the working fluid. The effects of wall superheat and wall wettability on bubbles’ nucleation, growth, and detachment in the evaporation chamber were compared and analysed. Moreover, the influence of the wall superheat on the thermal performance of the micro heat pipe was specifically examined. It is found that the low-level pool boiling occurs with a wall superheat that is higher than 0.357T c, indicating a high heat flux for heat removal. Interestingly, when the relatively hydrophobic chamber wall is superheated by 0.46T c, there are more nucleation sites, and the complete bubbles cycle containing nucleation, growth, and detachment is longer. In contrast, on a hydrophilic surface under the same and sufficient superheat condition, the number of bubble nucleation sites is less than that on the hydrophobic surface, and the complete cycle of bubbles is shorter. It is worth mentioning that the model has values for predictions of homogeneous nucleation of bubbles and thermal transport on hydrophobic or hydrophilic surfaces.

Grain size and shape fractal characteristics of gangue in the process of 'jaw breaking-ball milling'.

This study investigates the fractal characteristics of the particle size and shape distribution of gangue powder in the "jaw crushing-ball milling" process using mudstone gangue. For this, fractal theory, laser particle size analyzer, scanning electron microscope and other mesoscopic research methods were introduced. This study has several main factors, including the discharge port width in the jaw crushing stage, the grinding particle size, ball-to-powder ratio in the ball milling stage, and the fractal dimension changes of the gangue in different crushing stages. The results indicate that in the process of "jaw crushing-ball milling", gangue's particle size and shape fractal dimension values changed periodically. During the jaw crushing stage, the particle size fractal dimension increases with the width of the discharge opening, ranging from 1.85 to 1.92. The value of the shape fractal dimension varies from 2.65 to 2.84. Ball milling causes the fractal dimension value of gangue particle size to increase with time before agglomeration and decrease after agglomeration. By comparing different in-grinding particle sizes and ball-to-powder ratio, it is found that the fractal dimension value of gangue particle size decreases with the increase of in-grinding particle size and increases with the increase of ball-to-powder ratio. The final gangue's particle size fractal dimension value is concentrated between 2.5 and 2.8. The fractal dimension of particle shape increases with the increase of the grinding particle size, and decreases with the increase of ball-to-powder ratio. A ball-to-powder ratio greater than 6 gradually reduces its influence on fractal dimensions, and the final shape dimension lies between 1.06 and 1.16. In addition, the increase/decrease range of particle size and shape fractal dimension decreases with the increase of ball milling time, which is also consistent with the grinding kinetics theory. As a result of the changes in particle size and shape fractal dimensions, parameters such as jaw crusher discharge port width, grinding particle size, and ball-to-powder ratio are calculated to provide a theoretical basis for the entire crushing process in the "jaw crusher-ball milling" crushing process.

Active nematic liquid crystals simulated by particle-based mesoscopic methods.

Two Multi-particle collision dynamics algorithms that simulate nematic liquid crystals are generalised to reproduce active behaviour. One of the algorithms is due to Shendruk and Yeomans and is based on particles that carry an orientation vector ordered by a mean-field energy [T. N. Shendruk and J. M. Yeomans, Soft Matter, 2015, 11, 5101]. In the other algorithm, due to Mandal and Mazza, particles possess an order parameter tensor which evolves according to the Qian-Sheng model of nematohydrodynamics [S. Mandal and M. G. Mazza, Phys. Rev. E, 2019, 99, 063319]. For both methods activity is incorporated through a force proportional to the divergence of the local average order parameter tensor. Both implementations produce disclination curves in the nematic fluid that undergo nucleation and self-annihilation dynamics. Topological defects are found to be consistent with those observed in recent experiments of three-dimensional active nematics. Results permit to compare the length-scales over which the different nematic Multi-particle collision dynamics methods operate. The structure and dynamics of the orientation and flow fields agree with those obtained recently in numerical studies of continuum three-dimensional active nematics. Overall, our results open the opportunity to use mesoscopic particle-based approaches to study active liquid crystals in situations such as nonequilibrium states driven by flow or colloidal particles in active anisotropic solvents.

Simulating the flow of interacting ferrofluids with multiparticle collision dynamics.

Ferrofluid flow is fascinating since its fluid properties can conveniently be manipulated by external magnetic fields. Novel applications in micro- and nanofluidics as well as in biomedicine have renewed the interest in the flow of colloidal magnetic nanoparticles with a focus on small-scale behavior. Traditional flow simulations of ferrofluids, however, often use simplified constitutive models and do not include fluctuations that are relevant at small scales. Here we address these challenges by proposing a hybrid scheme that combines the multiparticle collision dynamics method for modeling hydrodynamics with Brownian dynamics simulations of a reliable kinetic model describing the microstructure, magnetization dynamics, and resulting stresses. Since both multiparticle collision dynamics and Brownian dynamics are mesoscopic methods that naturally include fluctuations, this hybrid scheme presents a promising alternative to more traditional approaches, also because of the flexibility to model different geometries and modifying the constitutive model. The scheme was tested in several ways. Poiseuille flow was simulated for various model parameters and effective viscosities were determined from the resulting flow profiles. The effective, field-dependent viscosities are found to be in very good agreement with theoretical predictions. We also study Stokes' second flow problem for ferrofluids. For weak amplitudes and low frequencies of the oscillating plate, we find that the velocity profiles are well described by the result for Newtonian fluids at the corresponding, field-dependent viscosity. Furthermore, the time-dependent profiles of the nonequilibrum magnetization component are well approximated by their steady-state values in stationary shear when evaluated with the instantaneous local shear rate. Finally, we also apply our scheme to simulate ferrofluid shear flow over a rough surface. We find characteristic differences in the nonequilibrium magnetization components when the external field is oriented in flow and in a gradient direction.