Dynamics Of Solid Particles Research Articles

Visualization experiment of solid-liquid two-phase flow transportation in a jet pump

Abstract Due to its lack of internal moving components, the jet pump offers widespread application possibilities in solid-liquid two-phase flow transportation. Utilizing high-speed photography, this research established a visual experimental platform for jet pumps, allowing for a detailed study and analysis of the dynamics of solid particles entering, mixing, and being conveyed through the jet pump. The following results were obtained. The introduction of solid phase particles into the jet pump results in decreased pressure ratio and efficiency, yet the general trajectory of change within the pump system remains constant. With decreasing particle size, particles become increasingly susceptible to being entrained and propelled into the jet pump by the high-velocity jet flow. The proportion of particle distribution in the mixing chamber rises as the flow ratio goes up. However, when the flow ratio falls below 0.6, the changes in particle distribution beneath the jet zone of the mixing chamber become insignificant, primarily due to the impact of particle deposition within the suction chamber. A reflux zone is observed in the throat, which gradually shrinks in length as the flow ratio increases.

Interfacial adsorption dynamics of solid lipid particles at oil/water interfaces through QCM-D technique

The interfacial adsorption dynamics of solid particles are important processes in the formation of Pickering emulsion, and its stabilities and functionalities are critically dependent on the particle interfacial structures. In this study, we investigated the interfacial behaviors of solid lipid particles (SLPs) within six food-grade SLPs using the quartz crystal microbalance with dissipation (QCM-D) technique. These SLPs had been subjected to surface modification with varying emulsifier contents, specifically 1, 2, and 4 wt% of both Polysorbate 40 (T40) and sodium caseinate (Na-Cas), referred to as T40-SLPs and Na-Cas-SLPs. Two distinct interface behaviors have been identified: Type 1, characterized by with weak interfacial activity, which included the 1 and 2 wt% T40-SLPs, and Type 2, exhibiting stronger interfacial activity, encompassing the 4 wt% T40-SLPs as well as the 1, 2 and 4 wt% Na-Cas-SLPs. Subsequently, the mechanism through which the emulsifiers influenced the interfacial dynamic behaviors was established by correlating the interfacial behaviors with the properties of SLPs. Briefly, larger and more electronegative spherical Na-Cas-SLPs exhibited stronger interfacial activity, which facilitated the formation of smaller and more stable Pickering droplets. The interfacial films formed by the short plate-like T40-SLPs were not sufficiently consolidated, which led to instability of the hydrophobic interfaces. These results were confirmed with macrostability tests of the Pickering emulsions stabilized by the SLPs and are expected to provide basic information for the functionalization of multicomponent Pickering emulsions.

Towards a better understanding of granular flows

Understanding the transport of particles immersed in a carrier fluid (bedload transport) is still an exciting challenge. Among the different types of gas–solid flows, when the dynamics of solid particles is essentially dominated by collisions between them, kinetic theory can be considered as a reliable tool to derive continuum approaches from a fundamental point of view. In a recent paper, Chassagne et al. (J. Fluid Mech., vol. 964, 2023, A27) proposed a two-fluid model based on modifications to a classical kinetic theory model (Garzó & Dufty, Phys. Rev. E, vol. 59, 1999, pp. 5895–5911). First, in contrast to the classical model, the model proposed by Chassagne et al. takes into account the interparticle friction not only in the radial distribution function but also through an effective restitution coefficient in the rate of dissipation term of granular temperature. As a second modification, at the top of the bed where the volume fraction is quite small, the model accounts for the saltation regime in the continuum framework. The theoretical results derived from the model agree with discrete simulations for moderate and high densities and they are also consistent with experiments. Thus, the model proposed by Chassagne et al. (J. Fluid Mech., vol. 964, 2023, A27) helps provide a better understanding of the combined impact of friction and inelasticity on the macroscopic properties of granular flows.

CFD simulations to study bed characteristics in gas–Solid fluidized beds with binary mixtures of Geldart-B particles: A qualitative analysis

The bed dynamics of unary and binary fluidized beds play a key role in understanding the pressure drop and hence provides an opportunity for performance improvement of the beds. In the present work, characteristics of fluidized beds with binary mixtures of Geldart-B particles were investigated using CFD simulations. The phenomena of segregation and mixing using simulations were studied, both qualitatively and quantitatively, at a range of superficial gas velocities (0.3–0.6 m/s) and two different bed heights. The study was divided into two parts. In Part I, the current study, a qualitative analysis of flow patterns for seven different binary mixtures, is presented. The quantitative analysis, including particle and gas velocity profiles, particle volume fraction profiles, and correlations for minimum fluidization velocity and pressure drop, will be presented in Part II of this work. A mathematical model consisting of an Eulerian-Eulerian model with RNG k-ε model and KTGF model to capture the bubble dynamics was used. The standardized values of coefficients and plastic stresses have been used for all simulations. The CFD model was validated using experimental data from the literature. Qualitative predictions of volume fraction profiles of small-sized particles showed that, for mixtures within a range of 40%–60% Geldart-B type large particles, the bubble and solid particle dynamics were different from those of single particles of the superficial gas velocities considered. In contrast to the single particles in the given superficial gas velocity range that were in bubbling regime, the binary particles showed a transition from bubbling to slugging to turbulent regime, as demonstrated by qualitative analysis. A homogeneous regime was observed for lower superficial gas velocities for mixtures consisting of 0%–20% large particles.

Geometric descriptors for the prediction of snowflake drag

The dynamics of solid particles of complex shapes such as airborne snowflakes are governed by aerodynamic drag forces that are a function of the relative velocity of the particle in the flow and the particle drag coefficient, which depends on the particle geometry and its orientation. In this study, artificial snowflakes are produced by additive manufacturing and their drag coefficients are obtained by measuring the terminal velocity in a liquid container, matching the Reynolds number typically encountered in natural occurrences. The experimental results show that the convex hull of the particle is suitable to accurately predict the drag force with existing correlations. Since it is unfeasible to accurately measure the three-dimensional geometries of natural snowflakes, the approximation with the convex hull provides a useful simplification. Furthermore, the known shapes of the artificial snowflakes are used to develop correlations to estimate the most relevant three-dimensional descriptors to predict the drag of snowflakes from a two-dimensional projection onto an arbitrary plane.Graphic abstract

Inertial Self-Assembly Dynamics of Interacting Droplet Ensembles in Microfluidic Flows.

The multiphase flow of droplets is widespread and used for both biological and nonbiological applications alike. However, the ensemble interactions of such systems are inherently nonlinear and complex, compounded by interfacial effects, making it a difficult many-body problem. In comparison, the self-assembly dynamics of solid particles in flow have long been studied and exploited in the field of inertial microfluidics. Here, we report novel self-assembly dynamics of liquid drops in microfluidic channels that contrast starkly with the established paradigm of inertial microfluidics, which stipulates that higher inertia leads to better spatial ordering. Instead, we find that ordering can be negatively correlated with inertia, while Dean flow can achieve long-range spatial periodicity on length scales at least 3 orders of magnitude greater than the drop diameter. Experimentally, we decouple droplet generation from ordering, enabling independent and systematic variation of key parameters, especially in ranges practical to droplet microfluidics. We find the inertia-dependent emergence of preferred drop separations and show that surfactant effects can influence the longitudinal ordering of multidrop arrays. The dynamics we describe have immediate utility to droplet microfluidics, where the ability to order drops is key to the streamlined integration of on-chip incubation with deterministic drop manipulation downstream─two important functions for biological assays. To this end, we demonstrate the use of passive inertial drop self-assembly to combine a delay line with picoinjection. These results not only present a largely unexplored direction for inertial microfluidics but also show the practical benefit of its unification with the versatile field of droplet microfluidics.

LBM modeling of solid particle dynamics in a viscous medium

This article discusses the mathematical and computer modeling of single solid particle dynamics in a viscous medium. The results of the study were obtained using a 3D numerical algorithm implemented on the basis of the D3Q19 model of the lattice Boltzmann method (LBM). The moving «liquid-solid» interface is accounted for using an interpolated bounce back (IBB) scheme. The velocity of a solid particle motion and the trajectory of a particle at Re = 1,56 are obtained. The results are in good agreement with the experimental and numerical results of other authors.

Computational prediction of microstructures in α‐alumina/PMMA composites and its experimental verification

AbstractProcessing, structure, property, and performance have been acknowledged in a linearly linked picture for materials manufacturing. It is promising to harness the processing‐structure relationship to accelerate the development of functional materials. In the present study, we attempted to predict microstructures of a polymer composite via computational simulations, because functions of the polymer composite would respond to its microstructures. A program KAPSEL, which has been widely utilized to calculate dynamics of solid particles in coherent fluids, was slightly amended to handle parameters related to interfacial science. Constituents of the target polymer composite were α‐alumina and poly(methyl methacrylate). When proper parameter values are given, the program yielded microstructural features similar to those found in an experiment. Nimbleness and affordability of the simulation scheme would allow us to omit experimental trial‐and‐error for functional polymer composites.

Study of sediment transport in the Jordão River, located in the mesoregion of the Triângulo Mineiro-MG

Hydrosedimentological studies are fundamental for the adequate management of water resources. The Jordão River, the research study area, has the potential to generate electricity to serve a region of the TriânguloMineiro and Alto Paranaíba. In this sense, the understanding of sediment transport resources is important, since it represents a fundamental contribution for ensuring adequate management of water resources in the region. This research study has the general objective of examining sediment transport in the Jordão River, with the aim of obtaining a preliminary understanding into the dynamics of solid particles in this water body. To this end, the determination of the key curves of Flow vs Sediment concentration, the characterization of the sediment granulometry and the hydraulic and geometric aspects of the studied stations, as well as the analysis of the factors that influence the dynamics of sediments in the river, will be carried out. For this purpose, four sampling stations were established, fourteen campaigns were carried out for flow measurements and water and sediment collections for the analysis of suspended and bed sediments in dry and rainy seasons from August 2017 to December 2018. A relationship between suspended sediment concentration and liquid discharge is found in the literature as Css = α·Qβ, at the four stations on the Jordan River during the measured period, with a value of 14.593 <α <26.904 and 0.6722 <β <0.9462, along with the graph representing all values Css = 22.944·Q0.6991. Noteworthy from the collections carried out is the relationship between rainy and dry seasons, where there is no increase verified in the filming of sediments with the increase in the flow of the river. Regarding the bed solids obtained through granulometric curves, there is a noted deposit of sediments with less granulometry in the dry season, mainly in seasons 3 and 4.

Experimental fluid dynamics of particles in a dielectric barrier discharge plasma-enhanced spouted bed

This study proposed the fluidized particles with dielectric barrier discharge (DBD) plasma in a slot-rectangular divergent-base spouted bed and focused on the dynamics of solid particles with the plasma irradiation. Two bed materials (Polypropylene (PP) particles and Polyamide (PA) particles) with same diameter (3 mm) were fluidized in this study. Fluidization parameters included gas velocity (7.4–14.9 m/s), particle amount (100–500), and plasma parameter (apply voltage, 0 and 7 kV) as the applied voltage were investigated here. Particle velocity profiles were analyzed through the methods of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Results show that the particle velocity was increased with the plasma irradiation, mainly by the enhancement in the vertical direction. The location of the highest particle velocity area related to the fluidization behavior of particles. With the increase of superficial gas velocity, the location of the highest particle velocity area raised along the central line but not reached the top of the solid bed. While the electron temperature of Ar plasma decreased with the addition of particles. Two electric fields (external electric field and surface charge electric field) presenting in the system were assumed to give the reason for the changes of the particle fluid dynamics.

Can preferential concentration of finite-size particles in plane Couette turbulence be reproduced with the aid of equilibrium solutions?

This work employs for the first time invariant solutions of the Navier-Stokes equations to study the interaction between finite-size particles and near-wall coherent structures. We consider horizontal plane Couette flow and focus on Nagata's upper-branch equilibrium solution (Nagata, 1990) at low Reynolds numbers where this solution is linearly stable. When adding a single heavy particle with a diameter equivalent to 2.5 wall units, we observe that the solution remains stable and is essentially unchanged away from the particle. This result demonstrates that it is technically feasible to utilize exact coherent structures in conjunction with particle-resolved DNS. While translating in the streamwise direction, the particle migrates laterally under the action of the quasi-streamwise vortices until it reaches the region occupied by the low-speed streak, where it attains a periodic state of motion. As a result of the ensuing preferential particle location, the time-average streamwise particle velocity differs from the plane-average fluid-phase velocity at the same wall-distance as the particle center, as previously observed in experiments and in numerical data for fully turbulent wall-bounded flows. Additional constrained simulations where the particle is maintained at a fixed spanwise position while freely translating in the other two directions reveal the existence of two equilibria located in the low-speed and in the high-speed streak, respectively, the former being an unstable point. A parametric study with different particle to fluid density ratios is conducted which shows how inertia affects the spanwise fluctuations of the periodic particle motion. Finally, we discuss a number of potential future investigations of solid particle dynamics which can be conducted with the aid of invariant solutions (exact coherent structures) of the Navier-Stokes equations.

Two-phase flow measurement of sub-millimeter sized particles falling in water with grid-generated turbulence

Sediment transport is one key process in sedimentation problems. The dynamics of sediments in rivers will lead to an ecological change of the catchment. Among all complicated processes in sediment transport, the settling dynamics of solid particles in the water contribute to the water quality and geomorphology of a river channel directly. This paper aims at an investigation of the interaction between particle movement and water flow, with application to hydro-environment situations such as transport of fine sand sediment in natural streams. The Stokes number in this type of application is much smaller than unity at which enhancement of particle settling velocity by strong ambient turbulence has been observed in many numerical and laboratory studies. The present laboratory study is conducted to study the settling of sub-millimeter sized heavy particles in water with a relatively weak grid-generated turbulence. The two-phase flow is measured with the whole-field imaging techniques of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). A two-camera PIV/PTV technique is used to obtain the instantaneous settling velocities of the solid particles and the turbulent water velocity field. Phase separation is based on an effective optical distinction of the two light scattering signals with fluorescent tagging on the solid particles. With this technique, it is found that in most cases of grid-generated turbulence the settling velocity of the heavy particles is slightly lower than the still water value. The falling heavy particles are also found to cause additional turbulence in the water with low ambient turbulence intensities. At one particular case of grid turbulence, the particles are found to fall with a depth-averaged settling velocity evidently higher than the still water value. The instantaneous turbulent fluid motions and particle trajectories tend to support the fast tracking effect to be related to the higher particle falling velocities.

Mimicking layer inversion in solid-liquid fluidized beds in narrow tubes

This paper investigates experimentally and numerically the dynamics of solid particles during the layer inversion of binary solid-liquid fluidized beds in narrow tubes. Layer inversion can happen in solid classifiers and biological reactors, where different solid particles coexist and segregation by diameter and density occurs. The fluidized beds were formed in a 25.4 mm-ID pipe and consisted of alumina and aluminum beads with diameters of 6 and 4.8 mm, respectively. We placed initially the lighter particles on the bottom in order to force an inversion of layers, mimicking the layer inversion mechanism. In the experiments, we filmed the bed with a high-speed camera and tracked individual beads along images, while in numerical simulations we computed the bed evolution with a CFD-DEM (computational fluid dynamics - discrete element method) code. We found the distances traveled by individual particles during the inversion and the characteristic time for layer inversion.

On the propagation and multiple reflections of a blast wave travelling through a dusty gas in a closed box

This paper concerns the propagation of shock waves in an enclosure filled with dusty gas. The main motivation for this problem is to probe the effect on such dynamics of solid particles dispersed in the fluid medium. This subject, which has attracted so much attention over recent years given its important implications in the study of the structural stability of systems exposed to high-energy internal detonations, is approached here in the framework of a hybrid numerical two-way coupled Eulerian-Lagrangian methodology. In particular, insights are sought by considering a relatively simple archetypal setting corresponding to a shock wave originating from a small spherical region initialized on the basis of available analytic solutions. The response of the system is explored numerically with respect to several parameters, including the blast intensity (via the related value of the initial shock Mach number), the solid mass fraction (mass load), and the particle size (Stokes number). Results are presented in terms of pressure-load diagrams. Beyond practical applications, it is shown that a kaleidoscope of fascinating patterns is produced by the “triadic” relationships among multiple shock reflection events and particle-fluid and particle-wall interaction dynamics. These would be of great interest to researchers and scientists interested in fundamental problems relating to the general theory of pattern formation in complex nonlinear multiphase systems.

Experimental study on dynamics of coherent structures formed by inertial solid particles in three-dimensional periodic flows.

We present experimental results obtained under normal gravity on the dynamics of solid particles in periodic oscillatory thermocapillary-driven flows in a non-isothermal liquid bridge made of decane. Inertial particles of different densities and in the size range approximately 0.75-75 μm are able to form stable coherent structures (particle accumulation structures, or PASs). Two image processing techniques were developed and successfully applied to compute time required for an ensemble of particles to form a structure. It is shown that the formation time grows with the decrease of the Stokes number. The observations indicate the probable irrelevance of the memory term for these experiments. Two types of PAS were observed-single (SL-I) and double-loop (SL-II)-which sometimes co-existed. Only large or very dense particles may form an SL-II type structure. A number of novel features of the system were perceived. In some cases, intermittently stable structures emerged (their dynamics is characterized by alternating time intervals during which a structure exists and is destroyed). Whereas in most experiments we observed a conventional symmetric and centered PAS, there were cases when a long-term stable asymmetric structure appeared. Experiments wherein two different types of PAS-forming particles were used simultaneously revealed the destructive role of collisions between the particles on formation of structures.

Measurement of Flow Characteristics in a Bubbling Fluidized Bed Using Electrostatic Sensor Arrays

Fluidized beds are widely applied in a range of industrial processes. In order to maintain the efficient operation of a fluidized bed, the flow parameters in the bed should be monitored continuously. In this paper, electrostatic sensor arrays are used to measure the flow characteristics in a bubbling fluidized bed. In order to investigate the electrostatic charge distribution and the flow dynamics of solid particles in the dense region, time and frequency domain analysis of the electrostatic signals is conducted. In addition, the correlation velocities and weighted average velocity of Geldart A particles in the dense and transit regions are calculated, and the flow dynamics of Geldart A and D particles in the dense and transit regions are compared. Finally, the influence of liquid antistatic agents on the performance of the electrostatic sensor array is investigated. According to the experimental results, it is proved that the flow characteristics in the dense and transit regions of a bubbling fluidized bed can be measured using electrostatic sensor arrays.

Wave machines and processes in drilling wells in complex hydrodynamic conditions

This paper presents mathematical models for describing the dynamics of solid particles in a wave field during drilling and rock colmatation in formations with low pressure. It is experimentally found that the efficiency of wave colmatation of a sandstone sample begins to significantly decrease at a differential pressure of less than 0.5 MPa and more than 1.4 MPa. Several versions of special drilling equipment have been developed.

Nonlocal systems of balance laws in several space dimensions with applications to laser technology

For a class of systems of nonlinear and nonlocal balance laws in several space dimensions, we prove the local in time existence of solutions and their continuous dependence on the initial datum. The choice of this class is motivated by a new model devoted to the description of a metal plate being cut by a laser beam. Using realistic parameters, solutions to this model obtained through numerical integrations meet qualitative properties of real cuts. Moreover, the class of equations considered comprises a model describing the dynamics of solid particles along a conveyor belt.

Lattice Boltzmann simulation of the three-dimensional motions of particles with various density ratios in lid-driven cavity flow

An estimation of solid particle dynamics through a fluid has been studied. Although traditional computational fluids dynamics models can predict multiphase flow and the interactions between the fluid and solid particles, a high level of accuracy of an appropriate numerical model for this type of difficulty is still in demand. Some researchers examining this problem dedicated their research to the particle motions under the influence of gravity. Therefore, in this study a modern computational fluid dynamic model, the Lattice Boltzmann Method (LBM), was proposed to predict the three-dimensional cubic lid-driven cavity flow and combined with the Lagrangian approach on the prediction of solid particles in the range of different density ratios. To solve the term, flow fluid, the mesoscale numerical scheme of the Multi Relaxation Time (MRT) lattice Boltzmann method was used to simulate the objects at higher stability. In the present study, the different densities of the particles were considered and the effects of gravity were included in the calculation. The 4th Runge-Kutta method was functioned to determine the effect of an external force on a particle because this method is accurate enough compared to other known numerical schemes. The hard sphere model was used to model particle-particle and particle-wall collisions. The solid particle subtleties determined using a numerical fluid dynamic simulation of LBM showed good agreement with the reputable benchmark results by previous researchers. Furthermore, according to the results, the dependency of the particle trajectories on the magnitude of the density of the particles can be observed. The results revealed the significant effect of collision, drag force, gravity force, and vortex structure on a particle's trajectory. Consequently, the LBM model is suitable for this type of problem, and the proposed model is expected to have a wide range of applications.

Numerical simulations of gas–liquid–particle three-phase flows using a hybrid method

For the analysis of debris behavior in core disruptive accidents of liquid metal fast reactors, a hybrid computational tool was developed using the discrete element method (DEM) for calculation of solid particle dynamics and a multi-fluid model of a reactor safety analysis code, SIMMER-III, to reasonably simulate transient behavior of three-phase flows of gas–liquid–particle mixtures. A coupling numerical algorithm was developed to combine the DEM and fluid-dynamic calculations, which are based on an explicit and a semi-implicit method, respectively. The developed method was validated based on experiments of water–particle dam break and fluidized bed in systems of gas–liquid–particle flows. Reasonable agreements between the simulation results and experimental data demonstrate the validity of the present method for complicated three-phase flows with large amounts of solid particles.