A multimass correction for multicomponent fluid flow simulation using smoothed particle hydrodynamics

In multicomponent fluid flow simulations using smoothed particle hydrodynamics, the Lagrangian particles used are mostly of equal mass. This is preferred over multimass particle setup (particles with different values of mass), as it resolves the fluid interfaces comparatively better. But the flip side of using uniform mass particle setup is that it may not be computationally economical in situations with large‐density ratios. Hence, using multimass particle setup is both economical and perhaps inevitable. An attractive feature of multimass particle setup is that it allows uniform resolution in regions with different values of density. To take advantage of the multimass setup, it is therefore imperative to reduce the error associated with its usage. In this work, we present suitable multimass correction terms and assess its effectiveness using the ?h–smooth particle hydrodynamics scheme. Standard benchmark problems, viz, shock tube test, triple‐point shock test, Rayleigh‐Taylor instability, and Kelvin‐Helmholtz instability were solved with multimass particle setup, where significant improvements could be achieved in resolving the associated contact discontinuities.     

Numerical simulation of particle flow in a sand trap

Sand traps are used to measure Aeolian flux. Since they modify the surrounding wind velocity field their gauging represents an important challenge. We use numerical simulations under the assumption of homogeneous turbulence based on FLUENT to systematically study the flow field and trapping efficiency of one of the most common devices based on a hollow cylinder with two slits. In particular, we investigate the dependence on the wind speed, the Stokes number, the permeability of the membrane on the slit and the saltation height.     

Lattice Boltzmann simulation of flow past a non-spherical particle

Lattice Boltzmann method was used to predict the fluid-particle interaction for arbitrary shaped particles. In order to validate the reliability of the present approach, simulation of flow past a single stationary spherical, cylindrical or cubic particle is conducted in a wide range of Reynolds number (0.1 < Re_p < 3000). The results indicate that the drag coefficient is closely related to the particle shape, especially at high Reynolds numbers. The voxel resolution of spherical particle plays a key role in accurately predicting the drag coefficient at high Reynolds numbers. For non-spherical particles, the drag coefficient is more influenced by the particle morphology at moderate or high Reynolds numbers than at low ones. The inclination angle has an important impact on the pressure drag force due to the change of projected area. The simulated drag coefficient agrees well with the experimental data or empirical correlation for both spherical and non-spherical particles.     

Application of particle simulation methods to composite materials: a review

Particle simulation methods represent deformation of an object by motion of particles, and their Lagrangian and discrete nature is suitable for explicit modeling of the microstructure of composite materials. They also facilitate handling of large deformation, separation, contact, and coalescence. Mesh-free particle methods will thus be appropriate for a part of issues throughout the lifecycle of composite materials despite their high calculation cost. This study focuses on three particle simulation methods, namely, smoothed particle hydrodynamics, moving particle semi-implicit method, and discrete element method, and reviews approaches for modeling composite materials through these methods. Applicability of each method as well as advantages and drawbacks will be discussed from the viewpoint of engineering of composite materials. This reviewing study suggests capability of particle simulation methods to handle multiphysics and to predict various complex phenomena that necessitate explicit modeling of the material’s microstructure consisting of reinforcements (inclusions), matrix, and voids.     

Solid particle impurity propagation in a fluid flow in a pipe

A longitudinal diffusion model is proposed for planar flow in which the fluid particles and the impurities have different velocities.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 5, pp. 847–853, May, 1979.     

PSO算法在舰船磁场磁体模拟中的应用

采用磁体模拟舰船磁场是一种常用且有效的方法，然而，过去磁模拟体位置的确定常依赖于人的经验，局限性较大。文中基于舰船磁场的磁偶板子模型，利用PSO算法对磁体的位置进行了优化。试验结果表明，该方法降低了人为经验对磁体模拟模型稳定性的影响，提高了磁体模拟法的精度。     

Squeezing flow of MHD fluid between parallel disks

Squeezing flow between parallel disks is studied for the case when one disk is porous and the other is impermeable. Viable similarity transform is used to reduce the problem to a highly nonlinear ordinary differential equation. Variation of Parameters Method (VPM) is then employed to determine the solution to resulting ordinary differential equation. Numerical solution is also obtained using R-K 4 method and comparison shows an excellent agreement between both the solutions. Effects of different physical parameters on the flow are also discussed with the help of graphs coupled with comprehensive discussions.     

Gas particle industrial flow simulation using RANSTAD

A turbulent gas particle finite-volume flow simulation of a representative coal classifier is presented. Typical values of the loading ratio permit a one-way coupling analysis. As a case study, the computational fluid dynamics code,ranstad, and the modelling aspects are discussed in some detail. The simulation indicates that small (≈ 30 μm) coal particles pass through the classifier to the furnace but that large (≈ 300 μm) particles are captured and remilled. The computational simulation indicates that the classifier performance can be improved by internal geometric modification. The commitment of the Electricity Commission of New South Wales (Pacific Power) to the exploitation of Computational Engineering for the improvement of all aspects of electricity generation is acknowledged.     

The flow of a viscoelastic fluid between two parallel plates with heat transfer

The problem of the flow of a third grade fluid between two parallel plates with heat transfer is studied. We prove that von Kármán type solutions are not admissible for a general third grade fluid, but it may be experienced by a particular subclass which we put in evidence. The existence, the uniqueness and the dependence on the little parameters a = RePr of the solution of the heat transfer problem are then analysed. Some numerical experiments concerning the first two approximations of the attached Taylor expansion of the solution of this problem are represented.     

Mathematical simulation of a twisted pseudoplastic fluid flow in a cylindrical channel

The results of investigations of a pseudoplastic fluid twisted flow in a cylindrical channel are presented. With increase in the shear stresses caused by the flow twisting, the effective viscosity decreases. As a result, in the axial part of the channel a zone of lower pressure is formed which, at smaller flow twisting, leads to the formation of the zone of backward flows.     

The simulation of particulate materials packing using a particle suspension model

The behavior of particulate composite materials, such as portland cement concrete, depends to a large extent on the properties of their main constituent—the aggregates. Among the most important parameters affecting the performance of concrete are the packing density and corresponding particle size distribution (PSD) of aggregates. Better packing of aggregates improves the main engineering properties of composite materials: strength, modulus of elasticity, creep and shrinkage. Further, it brings major savings due to a reduction in the volume of binder. A simulation algorithm was developed for the modeling of packing of large assemblies of particulate materials (of the order of millions). These assemblies can represent the real aggregate systems composing portland cement concrete. The implementation of the developed algorithm allows the generation and visualization of the densest possible and loose-packing arrangements of aggregates. The influence of geometrical parameters and model variables on the degree of packing and the corresponding distribution of particles was analyzed. Based on the simulation results, different PSDs of particulate materials are correlated to their packing degree.     

Modelling of a turbulent reacting gas/particle flow

Summary A mathematical model for two-phase turbulent reactive flows is presented which is based on considering both phases in Lagrangian manner. The mechanical and thermodynamical properties of the two-phase mixture are calculated along the trajectories of particles representing the system. Similar to Monte-Carlo methods for solving a high dimensional joint velocity-composition probability density function, the turbulent gas phase is described by means of stochastic calculus. The deterministic equations for individual solid particles can be treated directly. In this approach, the interaction between both phases is not smeared over computational cells but restricted to the vicinity of solid particles by the definition of an action-sphere which is attached to every solid particle. Applications of the method to isotropic, homogeneous turbulence indicate that it is capable of providing information on the local structure of combustion zones with species formation and transport. The results show that the method is applicable independent of the combustion modes in the gas phase, and it provides extensive statistics of various correlations of properties.     

A micromechanical model to predict the flow of soft particle glasses

Soft particle glasses form a broad family of materials made of deformable particles, as diverse as microgels, emulsion droplets, star polymers, block copolymer micelles and proteins, which are jammed at volume fractions where they are in contact and interact via soft elastic repulsions. Despite a great variety of particle elasticity, soft glasses have many generic features in common. They behave like weak elastic solids at rest but flow very much like liquids above the yield stress. This unique feature is exploited to process high-performance coatings, solid inks, ceramic pastes, textured food and personal care products. Much of the understanding of these materials at volume fractions relevant in applications is empirical, and a theory connecting macroscopic flow behaviour to microstructure and particle properties remains a formidable challenge. Here we propose a micromechanical three-dimensional model that quantitatively predicts the nonlinear rheology of soft particle glasses. The shear stress and the normal stress differences depend on both the dynamic pair distribution function and the solvent-mediated EHD interactions among the deformed particles. The predictions, which have no adjustable parameters, are successfully validated with experiments on concentrated emulsions and polyelectrolyte microgel pastes, highlighting the universality of the flow properties of soft glasses. These results provide a framework for designing new soft additives with a desired rheological response.     

A modified drag model for power-law fluid-particle flow used in computational fluid dynamics simulation

A modified drag model for the power-law fluid-particle flow considering effects of rheological properties was proposed. At high particle concentrations (ε_s ≥ 0.2), based on the Ergun equation, the cross-sectional shape and the tortuosity of the pore channel are considered, and the apparent flow behavior index and consistency coefficient of the power-law fluid at the surface of the particles are corrected. At low particle concentrations (ε_s < 0.2), based on the Wen-Yu drag model, the modified Reynolds number for power-law fluid and the relational expression between drag coefficient for single particle and Reynolds number that considers the effect of the flow behavior index are adopted. Numerical simulations for the power-law fluid-particle flow in the fluidized bed were carried out using the non-Newtonian drag model. The effects of rheological parameters on the drag coefficient were analyzed. The comparisons of simulation and experiment show that the modified drag model predicts reasonable void fraction under different rheological parameters, particle diameters, and liquid velocities in both low particle concentrations and high particle concentrations. The increase in flow behavior index and consistency coefficient increases the drag coefficient between the two phases and decreases the average particle concentration within the bed.     

Effective potential method in a cellular fluid model. Application to binary fluid systems

A method is proposed to analyze the thermal properties of fluids and their mixtures, which is based on using the effective potential (12,6) with variable potential parameters in conjunction with the equation of state for a cellular model.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 2, pp. 316–323, August, 1979.     

Numerical model of a parallel flow minichannel evaporator with new flow boiling heat transfer correlation

In this paper, a distributed parameter (DP) numerical model with the new proposed flow boiling heat transfer correlation was established for parallel flow minichannel (PFMC) evaporator. DP model validation was made by comparing the measured values obtained on experimental studies, which were conducted under refrigerant mass flow rate range of 34.6–245.6 kg h⁻¹ and evaporation pressure of 200–500 kPa. The effects of four different flow boiling heat transfer correlations on DP model performance were investigated. Results showed that the new correlation predicted 99% of experimental data in ± 30% error bands. Moreover, the DP model with the new correlation yielded the mean absolute error (MAE) of 1.5%, 9.1%, 18.8%, 14.2% and 19.8% in prediction of cooling capacity, outlet air temperature, refrigerant superheat, air side and refrigerant side pressure drop, respectively. The presented DP model can be implemented to evaluate the performance of PFMC evaporator, and therefore can save efforts on component and system design and optimization.     

The uses of a simulation model in studying a sequencing problem in a batch/flow environment

This paper considers the modelling of an actual batch/flow environment and discusses in detail the basic production system used in this study and its associated sequencing problem. The approach adopted for this problem is outlined and the concept behind the use of a simulation model as a day-to-day tool for production control is discussed. Finally, the limitations of such an approach for a large but fairly stable production unit are presented.     

Pulsating flow of a couple stress fluid in a channel with permeable walls

The paper is concerned with an analytical study of the oscillatory flow of a couple stress fluid in a channel, bounded by two permeable walls. The couple stress fluid is considered to be injected into the medium through one of the walls with a given velocity and to be sucked off by the other wall with an equal velocity. The problem is solved by using a perturbation technique. Analytical expressions for the velocity and volumetric flow rate are derived for the oscillatory flow of the couple stress fluid flowing in the channel. By using the method of parametric variation, distribution of the velocity of the couple stress fluid, change in velocity profiles at different instants of time, change in volumetric flow rate with change in frequency and cross-flow Reynolds number are computed, by considering an illustrative example. The study reveals that both the velocity and the volumetric flow rate are quite sensitive to the couple stress parameter, the frequency of oscillation and also to the cross-flow Reynolds number. The study will be immensely useful in resolving different problems associated with oil industries.     

Direct numerical simulation of ignition of a single particle freely moving in a uniform flow

In this study, a direct numerical simulation (DNS) of the ignition of a single particle freely moving in a uniform flow is performed to investigate the particle’s ignition behavior in detail. The Arbitrary Lagrangian-Eulerian (ALE) method is employed to compute the six degrees of freedom motion of a particle (Zhang et al., 2015). The computational setting follows the experiment designed by Lee and Choi (2015). The volatile gas that is composed of methane blows out at the particle surface. Its velocity is calculated by Ex-CPD model (Umemoto et al., 2017) and its direction is set perpendicular to the particle surface. The ignition behavior is compared with that observed in the experiment. The effect of the particle’s shape is also investigated. Results show that the ignition delay of the particle and the flame inclined angle are in good agreement with that of the experiment. While examining the combustion of the gas phase by considering the variation of Flame Index (FI), it is found that a premixed and diffusion regions are formed around the particle after the devolatilization starts. The gas phase ignites at the boundary of the premixed and diffusion regions and the flame propagates towards the particle. This causes a rapid increasing of the temperature and the volatile velocity on the particle surface. Finally, a diffusion flame is formed and reaches a stable state around the particle. It is also revealed that the flame keeps spherical despite the spheroidal shape of the particle.     

MHD boundary-layer flow of a non-Newtonian fluid over a continuously moving surface with a parallel free stream

Summary The MHD flow and heat transfer of a non-Newtonian power-law fluid over a continuously moving surface with a parallel free stream have been investigated. The partial differential equations governing the non-similar flow have been solved numerically using an implicit finite-difference scheme. The skin friction and heat-transfer coefficients increase with the magnetic parameter, and they are more for the pseudoplastic fluid than for the dilatant fluid. The heat-transfer coefficient increases significantly with the Prandtl number. The gradient of the velocity at the surface is negative when the wall velocity is greater than the free stream velocity, and it is positive when the wall velocity is less than the free stream velocity.