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The study is concerned with the understanding of elliptical particles' transport behavior coupled with heat transfer effects. A combination of immersed boundary and lattice Boltzmann method is utilized to simulate the problem. A complementary repulsive force method is hired to treat the collision among particles and walls. The direct forcing and direct heating immersed boundary–lattice Boltzmann method due to their promising results in the case of particle-laden flows have been employed to determine hydrodynamic force and energy exchange among particles and flow. The Boussinesq approximation is used for coupling the flow field and temperature. The effect of particle acceleration is also involved. Various cases and configurations including hot and cold elliptical and circular particles are investigated. The results are properly validated against the available literature data. Effects of dimensionless numbers like Prandtl and Grashof number on particles' settling velocities and transport manners are studied. From the results, it is found out that thermal properties can strongly influence the settling behavior of particles. The higher values of Grashof and Prandtl numbers for hot particles have a negative influence on the sedimentation velocity. It is also shown that hot particles have a tendency to attract each other. A complete comparative test including the influence of shape, wall effect, collision force, and energy is carried out. [ABSTRACT FROM AUTHOR]

In this study, lattice Boltzmann method (LBM) is used to investigate liquid water transport in a gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells (PEMFC) by considering mixed wettability. The GDL is reconstructed using the stochastic method and the simulations are performed to explore liquid water behaviors in the GDL. In this study, the dynamic behavior of liquid water during removal from gas diffusion layer of a PEMFC electrode is analyzed. The results are related to the water management and the optimal design of the GDL. The effects of inserted hydrophilic layer on the removal process and water distribution are investigated and a wettability‐tailored GDL is proposed. In addition, liquid water dynamic behaviors and liquid water saturation within the GDL in steady state and transient mode are explored. The effects of mixed wettability on the effective clusters in GDL, merging of different clusters and the loops developed by the fingers are investigated in detail. The optimum thickness and optimum location for the inserted hydrophilic layer inside the GDL are also proposed. The results show that combination of hydrophilic layer with the hydrophobic pores leads to an increase in the performance of the PEMFCs. In other words, the water management in GDL can be suitably done by selection of location and thickness of inserted hydrophilic layer. Regarding different test cases, the optimum location of the inserted hydrophilic layer is GDL‐GC interface with the optimum thickness of 12.5% of GDL thickness. [ABSTRACT FROM AUTHOR]

An immersed boundary (IB)-lattice Boltzmann method (LBM) combined with a robust lattice spring model (LSM) was developed for modeling fluid–elastic body interactions. To include the effects of viscous flow forces on the deformation of a flexible body, rotational invariant springs were connected regularly inside the deformable body with square lattices. Fluid–solid interactions were due to an additional force density in the lattice Boltzmann equation enhanced by the split-forcing approach. To check the validity and accuracy of the numerical method, the flow over a rigid plate and the deformation of a cantilever beam were investigated. To demonstrate the capability of the new method, different test cases were examined. The deformation of a two-dimensional flexible vertical plate in a laminar cross-flow stream at different conditions was analyzed. The simulations were performed for different boundary conditions imposed on the elastic plate, namely, fixed-end corners and fixed middle point. Different flow conditions such as “steady flow regime”, “vortex shedding flow regime”, and the limit of “rigid body motion” were examined using the new IB-LBM-LSM approach. A general formulation for evaluating the deformation of the elastic body was also introduced, in which the position of the LSM nodes (inside the body) was updated implicitly at each time step. Two dimensionless groups, namely capillary number ( Ca ) and Reynolds number ( Re ), were used for parametric study of the behavior of the flow around the deformable plate. It was found that for low Reynolds numbers ( Re   <  50) and when the middle of the plate was fixed, decreasing the capillary number led to a decrease in the drag coefficient. The fluctuation of the plate during the vortex shedding flow regime was also explored. It was found that when the middle of the plate was fixed, the critical Reynolds number for the initiation of vortex shedding increased. For Re > 100, the Strouhal number was observed to increase with the decrease in capillary number. [ABSTRACT FROM AUTHOR]

The study of fluid front in porous media in enhanced oil recovery is important. The purpose of this study is to simulate water flooding, and investigate the factors affecting the fluid front across a microfracture and simple porous media using Shan-Chen type of the Lattice Boltzmann Method (LBM). Various factors, including velocity and dynamic viscosity that define the capillary number and wettability are considered. Independently, the increase in velocity and dynamic viscosity ratio results in viscous fingering and its narrowness. Increasing the wettability of the displacing fluid decreases viscous fingering, and as a result, it makes the fluid move in piston form. The lowest sweep efficiency occurs when the displacing fluid has a neutral wettability. Simulation results show the strength and accuracy of Shan-Chen type of LBM in fluid front tracking in porous media in pore scale. [ABSTRACT FROM AUTHOR]

In this study a direct numerical simulation methodology for investigating the transient non-isothermal sedimentation of circular particles in non-Newtonian fluids was developed. The combined method of direct-forcing immersed boundary and non-Newtonian lattice Boltzmann method (IB-NLBM) with split-forcing algorithm was used for simulating fluid-particle interactions including the thermal effects. The 4-point diffuse interface scheme was used to link the fixed Eulerian nodes of fluids to the moving Lagrangian nodes of immersed boundary. The effects of added mass due to the particle acceleration were also included in the analysis. The accuracy of the method was successfully validated by comparison of the model predictions with experimental data and earlier numerical results for cold and hot falling particles. The effects of non-Newtonian power-law index and temperature-dependent viscosity of shear-thinning and shear-thickening fluids on settling particles at fixed or varying temperatures for different generalized Archimedes and Prandtl numbers were also investigated. The results for shear-thinning fluids indicated that the effect of temperature-dependent viscosity was more noticeable at higher value of non-Newtonian behaviour index. Furthermore, the differences between the cases of constant and varying particle temperature were more noticeable at higher non-Newtonian behaviour index and larger values of generalized Prandtl number. [ABSTRACT FROM AUTHOR]

In the current study, a direct-forcing immersed boundary–non-Newtonian lattice Boltzmann method (IB–NLBM) is developed to investigate the sedimentation and interaction of particles in shear-thinning and shear-thickening fluids. In the proposed IB–NLBM, the non-linear mechanics of non-Newtonian particulate flows is detected by combination of the most desirable features of immersed boundary and lattice Boltzmann methods. The noticeable roles of non-Newtonian behavior on particle motion, settling velocity and generalized Reynolds number are investigated by simulating benchmark problem of one-particle sedimentation under the same generalized Archimedes number. The effects of extra force due to added accelerated mass are analyzed on the particle motion which have a significant impact on shear-thinning fluids. For the first time, the phenomena of interaction among the particles, such as Drafting, Kissing, and Tumbling in non-Newtonian fluids are investigated by simulation of two-particle sedimentation and twelve-particle sedimentation. The results show that increasing the shear-thickening behavior of fluid leads to a significant increase in the kissing time. Moreover, the transverse position of particles for shear-thinning fluids during the tumbling interval is different from Newtonian and the shear-thickening fluids. The present non-Newtonian particulate study can be applied in several industrial and scientific applications, like the non-Newtonian sedimentation behavior of particles in food industrial and biological fluids. [ABSTRACT FROM AUTHOR]

This study is concerned with the non-Newtonian fluid flow over stationary obstacles of different shapes and sedimentation of particles in non-Newtonian liquids. The direct-forcing immersed boundary – Lattice Boltzmann method is used and the flows of non-Newtonian fluids including the pseudo-plastic and dilatant fluids in the vicinity of circular, square and triangular disks are studied. The proposed direct numerical method employs the split-forcing algorithm for considering the presence of Lagrangian boundary points on a fixed Eulerian fluid domain. Unlike the previously used methods, the effects of added mass due to particle acceleration are included in the analysis. The validation tests for both stationary and moving cylinders with cross-sections of different shapes immersed in Newtonian fluids are presented. The effects of the number of forcing points on a generalized Reynolds number are investigated by utilizing two to six points in the diffuse interfaces. The results show that the increase of shear-thinning behavior and the number of sides of a cross-section׳s shape slightly decrease the accuracy of solutions. The number of forcing points, however, has no significant effect on the hydrodynamics parameters. The high accuracy and the simplicity of implementation of the presented method may make it attractive for solving problems involving non-Newtonian fluid flow near stationary and/or moving boundaries with different shapes with application to drug delivery in biological systems, fluidized bed reactors, and polymer processing operations. [ABSTRACT FROM AUTHOR]

Natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method (LBM). The physics of flow and energy transfer in open end cavities are addressed when the hot wall is inclined. The combination of the two topics (open cavity and inclined walls) is the main novelty of the present study. The effects of the angle of the hot inclined wall on the flow field and heat transfer are thoroughly investigated. The Prandtl number is fixed to 0.71 (air). The Rayleigh number and the angle of the hot inclined wall are varied in the range of 10 to 10 and 60° to 85°, respectively. The results are presented for two different aspect ratios, i.e., A = 1 and 2. The results obtained with the LBM are also compared with those of the finite volume method (FVM). The predicted results of the LBM conform to those of the FVM. The results show that by increasing the angle of the hot inclined wall and the aspect ratio of the cavity, the average Nusselt number decreases. The trend of the local Nusselt number on the inclined wall is also discussed. [ABSTRACT FROM AUTHOR]

In this study, the immersed boundary-thermal lattice Boltzmann method has been used to simulate non-Newtonian fluid flow over a heated circular cylinder. The direct-forcing algorithm has been employed to couple the off-lattice obstacles and on-lattice fluid nodes. To investigate the effect of boundary sharpness, two different diffuse interface schemes are considered to interpolate the velocity and temperature between the boundary and computational grid points. The lattice Boltzmann equation with split-forcing term is applied to consider the effects of the discrete lattice and the body force to the momentum flux, simultaneously. A method for calculating the Nusselt number based on diffuse interface schemes is developed. The rheological and thermal properties of non-Newtonian fluids are investigated under the different power-law indices and Reynolds numbers. The effect of numerical parameters on the accuracy of the proposed method has been investigated in detail. Results show that the rheological and thermal properties of non-Newtonian fluids in the presence of a heated immersed body can be suitably captured using the immersed boundary thermal lattice Boltzmann method. [ABSTRACT FROM AUTHOR]

Highlights: [•] A porous block is considered in the channel for analysis of non-Newtonian fluids. [•] Both regular and random arrangements of fibers are employed in the channel. [•] The Nusselt number for both arrangements are presented using ‘confidence interval’. [•] Several blockage ratios with different arrangements are checked to obtain a correlation. [•] The method is verified through comparison with existing results. [Copyright &y& Elsevier]

The main goal of the present study is to investigate the heat transfer enhancement in a channel partially filled with an anisotropic porous block (Porous Foam) using the lattice Boltzmann method (LBM). Combined pore level simulation of flow and heat transfer is performed for a 2D channel which is partially filled with square obstacles in both ordered and random arrangements by LBM which is not studied completely in the literature. The effect of the Reynolds number, different arrangements of obstacles, blockage ratio and porosity on the velocity and temperature profiles inside the porous region are studied. The local and averaged Nusselt numbers on the channel walls along with the respective confidence interval and comparison between results of regular and random arrangements are presented for the first time. For constant porosity and block size, the maximum value of averaged Nusselt number in the porous block is obtained in the case of random arrangement of obstacles. Also, by decreasing the porosity, the value of averaged Nusselt number is increased. Heat transfer to the working fluids increases significantly by increasing the blockage ratio. Several blockage ratios with different arrangements are checked to obtain a correlation for the Nusselt number. [ABSTRACT FROM AUTHOR]

In the present paper, a Lattice-Spring-Damper-Model (LSDM) is proposed to analyze the interactions between elastic (viscoelastic) structures and fluid flow by implementing the framework of the Immersed Boundary-Lattice Boltzmann Method. Lattice Boltzmann Method is employed for the simulation of the fluid domain, and as for deformable structures analysis, the "mass-spring-damper" network is proposed. In this study, a series of viscous dampers is added in mass-spring network to produce a viscoelastic solid network. This network can be readily converted into an elastic network and is able to cover various properties such as elastic modulus, bending rigidity, and rheological characteristics of viscoelastic solids. Moreover, some critical rheological tests such as creep test, oscillation test, and relaxation test are checked in the viscoelastic solids by the proposed method. To check the ability of the proposed model, the flapping dynamics of a viscoelastic filament is considered in the presence of fluid flow. Since most numerical studies have investigated the movement of the elastic filaments, this study is mainly focused on the simulation of viscoelastic deformable filaments. The elastic/viscoelastic filaments' flapping regime are assessed and the effects of Reynolds number and geometrical parameters of the deformable filaments are analyzed and checked with the available data in the literature. Results show that the behavior of real elastic structures and viscoelastic bodies can be properly analyzed by the proposed LSDM by considering their rheometric features. • Novel numerical model is proposed for simulation of elastic and viscoelastic structures. • A Lattice-Spring-Damper-Model (LSDM) is proposed for FSI problems. • Movement of deformable filaments are studied by proposing LSDM. • Immersed boundary lattice Boltzmann method is analyzed in combination with LSDM. [ABSTRACT FROM AUTHOR]

The article discusses the lattice Boltzmann method used to simulate non-Newtonian fluid flow and the immersed boundary method. It cites on the wide application of particle flows in industries and sciences considering a non-Newtonian behaviors. The article also discusses the consideration of non-Newtonian flow over a stationary cylinder and channel filled with non-Newtonian fluids.

The present study applied Lattice Boltzmann method (LBM) for examining the transport of liquid water in a GDL carbonic paper of polymer electrolyte membrane (PEM) fuel cells. The stochastic method is used for GDL carbonic paper reconstruction. In order to study the behavior of liquid water, different simulations are carried out on the reconstructed GDL. While removing from the GDL of a PEM fuel cell, the dynamics of liquid water is simulated by LBM in this study. The effects that the wettability of GDL imposes on the removal process and liquid water distribution are investigated. In addition, the dynamic behaviors and the saturation process of the liquid water in GDL in a steady state and a transient mode are also explored. The effects of surface wettability on the effective clusters in GDL, merging of different clusters and the loops developed by the fingers are investigated. Moreover, the effects of mixed wettability on the liquid water dynamic behavior and liquid water saturation within the GDL are studied in detail. The results show that the best location for insertion of the hydrophilic layer inside the GDL is near the GDL-GC interface. In this case, the time required for liquid water to reach the GDL/GC interface is reduced about 17% than purely hydrophobic GDL. A decrease of 18.7% in the steady-state saturation level is also observed by insertion of hydrophilic layer; therefore, use of hydrophilic layer near GDL-GC interface is more effective than increasing the contact angle of GDL-fibers. Different validation studies are also reported to show the accuracy of the model. [ABSTRACT FROM AUTHOR]