Particles In Fluid Flow Research Articles

Water Quality Modeling of Wastewater Discharges for Prediction of Sediment Transport and Deposition in Surface Water

Sediment deposition in surface water bodies can have a range of significant impacts, affecting everything from the aquatic ecosystem to water quality and infrastructure. It can affect the availability of food sources for aquatic organisms; and change the physical structure of habitats, such as riverbeds and lake bottoms. It can equally smother aquatic plants and animals, leading to a decline in biodiversity. A model of the governing equations of particle motion and fluid flow was developed with COMSOL Multiphysics 5.3a. With a coefficient of determination of 0.99, the model result demonstrated good agreement after result validation using experimental data. According to study findings, sediments in the study area, Ele River move more slowly than sediments in the midstream which causes a high deposition of sediments at the river banks. This sediment deposition affects the irrigation system for crop production considering the ability of the sediments to block sprinkler nozzles which limits it from supplying sufficient water for the production of crops.

DDPM investigation on centrifugal slurry pump with inlet and sideline configuration retrofit

The inlet and sideline configuration modifications are widely investigated to alter regional particle fluid flow conditions, considering pressure, turbulence and erosion, therefore to improve energy saving and compartment longevity of centrifugal slurry pump. This paper aims to analyse pump hydraulic and erosion characteristics with proposed pump sideline and inlet configuration retrofit by the DDPM method. Specifically, the inlet guide vane number () and angle (), and sidelining vane (SDV) curvature are investigated in quantitative manner. Accordingly, by adjusting inlet vane configuration and placement, a trade-off between wall erosion and hydraulic performance is observed. The sidelining vane (SDV) design is suggested to avoid resultant counter-current flow formulation, therefore, to mitigate turbulence induced erosion in impeller and volute. However, the SDV modification effect on pump hydraulic head and efficiency is found marginal. In general, this study offers realistic guideline for performance improvement and device upgrading of centrifugal slurry pumps.

Particle-resolved direct numerical simulation and bottom-up statistical analysis on solid-phase pressure in particle–fluid systems

Solid-phase stress is a major factor shaping the complex behaviors of particle–fluid systems. However, uncertainties and inconsistencies can be found among the various models proposed. This work pays attention to the effect of mesoscale structures, that is, the heterogeneity of particle distribution at a scale of statistical meaning but no significant flow field variation, on the solid-phase normal stress, or pressure. Using a bottom-up statistical method, the solid-phase pressure in liquid- and gas–solid flows is investigated by particle-resolved direct numerical simulation (PR-DNS). It is found that, in almost uniform liquid–solid flows, the solid-phase pressure is not well predicted by classical kinetic theory of granular flow (KTGF) due to the presence of interphase force, although KTGF applies much better to single-phase granular flows. In gas–solid flows, with increasing heterogeneity described by structural functions, the statistical solid-phase pressure becomes significantly larger than that in corresponding homogeneous flows. It reveals that mesoscale structures strongly affect solid-phase pressure, and suggests the deviation from classical KTGF in heterogeneous gas–solid flows can be attributed to both the interphase forces (mainly drag) and mesoscale structures. The coefficients in the solid-phase pressure models in KTFG are modified, fitting the statistical results of both homogeneous and heterogeneous particle–fluid flows.

A new evaluation method for sand control performance of slotted screen

Evaluation method of slotted screen performance is a critical concern for sand control. Despite its significance, comprehensive investigations into quantitative study of sand retaining during the complex flow process need further in-depth study, particularly in numerical simulation research model of the slotted screen. This paper adopts the two-way coupling calculation method of computational fluid dynamics (CFD) and discrete element method (DEM) for the particle movement and fluid flow at the slotted screen and establishes a numerical model of the sand particle migration process through the slotted screen. The sand particle deposition and plugging dynamics on the surface of the sand retaining medium and the micro sand plugging mechanism and blockage pattern are studied. The fractal dimension of formation sand is introduced to characterize different distribution of formation sand. The effects of fluid viscosity, width of the slotted screen, sand production concentration, fluid velocity and particle size distribution on sand production, sand passing rate and particle size distribution of formation sand passing through the slot and plugging behavior are studied. The sand plugging process of slotted screen can be divided into three stages: the beginning of blockage, the intensification of blockage, and the balance of blockage. Under simulated conditions, the initial sand plugging rate is 87%, and as the blockage intensifies, the sand plugging rate gradually increases to 96.5%. Based on the analysis of numerical simulation results, the index of total seepage resistance damage amplitude and velocity, general sand retention ratio and passed-sand size were defined to construct the integrated evaluation method of slotted screen media, which involves the performance of sand retention, anti-plugging and flow ability. A brand new set of ideas on quantifying the integrated evaluation method were introduced to calculate the individual and integrated performance indicators of the slotted screen based on simulated data. The quantitative evaluation of the sand control performance of the slotted screen provides guidance and reference for the parameter design of the slotted screen in the target oil region and the accuracy optimization of the sand control medium.

CFD-DEM investigation of centrifugal slurry pump with polydisperse particle feeds

Polydisperse particle feed into centrifugal slurry complicates hydraulic performance and wall erosion but is poorly understood. This paper presents a numerical study of a centrifugal slurry pump, focusing on the effect of particle size distribution (PSD) using the combined computational fluid dynamics and discrete element method (CFD-DEM). It incorporates rigid impeller rotation and wall erosion. On this basis, the hydraulic and erosion model validity is verified by clear water performance and jet erosion test, respectively. Additionally, this CFD-DEM model is compared with the dense discrete phase model (DDPM), demonstrating more precise erosion prediction as its fully resolved particle-particle interactions. Generally, total pump erosion severity intensifies when the PSD is broadened. Compartment-wise, it indicates the necessity of tailoring flow structure to enlarge drag force, therefore, mitigate particle aggregation in the impeller. This in-house CFD-DEM model is promising for addressing particle-fluid flow problems in centrifugal pumps or coupling with data driven method.

Evaluation of the prediction capability of mesoscale CFD models on velocity fluctuations in liquid-solid flows

Mesoscale CFD models are of great importance in multiphase flow studies due to their acceptable computational cost and great numerical fidelity. However, the evaluations of mesoscale models on velocity fluctuation predictions are still limited. An evaluation of the predictive capability of current CFD models on velocity fluctuations in liquid-solid flows is presented. Numerical simulations are carried out with both the Eulerian-Eulerian Two-Fluid Model (TFM) and the Eulerian-Lagrangian Discrete Phase Model (DPM), and compared with the available experimental data. Together with the proper models in both phases, the TFM satisfactorily predicts two-phase velocity fluctuations. A diffusion-based coupling method is implemented to mitigate the grid dependency problem in the DPM. The diffusion-based coupling method greatly improves the predictive fidelity of the particle volume fraction for DPM. However, it overpredicts velocity fluctuations for both phases. Further research is required to enhance the fidelity of velocity fluctuation prediction in fluid-particle flow simulation models.

Dynamics and sorting of run-and-tumble particles in fluid flows with transport barriers

We investigate the dynamics of individual run-and-tumble particles in a convective flow which is a prototype of fluid flows with transport barriers. We consider the most prevalent case of swimmers denser than the background fluid. As a result of gravity and the effects of the carrying flow, in the absence of swimming the particles either sediment or remain in a convective cell. When run-and-tumble also takes place, the particles may move to upper convective cells. We derive analytically the probability of uprise. Since that probability in a given fluid flow can vary strongly across species, our findings inspire a purely dynamical mechanism for species extraction in the dilute regime. Numerical simulations support our analytical predictions and demonstrate that a judicious choice of the fluid flow’s parameters can lead to particle sorting with an arbitrary degree of purity.

Modulation instability analysis, and characterize time-dependent variable coefficient solutions in electromagnetic transmission and biological field

This study integrates the telegraph model with the traveling wave coefficient. This model characterizes planar random motion of particles in fluid flow, pressure waves from pulsatile blood flow in arteries, electrical impulses in nerve and muscle cell axons, and electromagnetic waves in superconducting media. Using the efficient and well-established Enhanced Modified Simple Equation (EMSE) method, we investigate solitary wave solution with the variable coefficient of the telegraph model. To investigate the variable coefficient solitary wave solution, we apply a transformation variable η = h(t)x + g(t), which is dependent on the time variable function. The diverse functions of h(t) and g(t) yield many novel and exclusive solutions. Numerical solutions are plotted in 3D, density, and 2D. instanton soliton, kinky periodic wave, lump wave, kink wave, anti-kink wave, double periodic wave, diverse types periodic wave, lump with bell wave periodic wave, periodic lump wave, etc. Solitary waves explain complex wave phenomena through nonlinear effects like self-interaction and dispersion. Due to the classical nonlinear telegraph model's wave dynamics, they are used in brain function and communication system design. We conclude by testing the governing model's modulation instability. Dispersive and nonlinear processes modulating the stable state cause instability in high-order nonlinear equations. Examining the wave movement role and modulation instability analysis to assess solution stability shows that all solutions are accurate and stable. The computational difficulties and results demonstrate the approaches' clarity, effectiveness, and simplicity, suggesting they can be applied to evolutionary dynamic and static nonlinear equations in computational physics, other real-world situations, and numerous academic disciplines.

Two-temperature modeling of lamellar cathode arc

A three-dimensional, two-temperature (2T) model of a lamellar cathode arc is constructed, drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell’s equations. The model aims to elucidate how the physical properties of electrons and heavy particles affect heat transfer and fluid flow in a lamellar cathode arc. This is achieved by solving and comparing the fields of electron temperature, heavy particle temperature, fluid flow, current density, and Lorentz force distribution under varying welding currents. The results show that the guiding effect of the lamellar cathode on current density, the inertial drag effect of moving arc, and the attraction effect of Lorentz force at the lamellar cathode tip primarily govern the distribution of the arc’s physical fields. The guiding effect localizes the current density to the front end of the lamellar cathode, particularly where the discharge gap is minimal. Both the inertial drag effect and the attraction effect of Lorentz force direct arc flow toward its periphery. Under the influence of the aforementioned factors, the physical fields of the lamellar cathode arc undergo expansion and shift counter to the arc’s direction of motion. A reduction in welding current substantially weakens the guiding effect, causing the arc’s physical fields to deviate further in the direction opposite to the arc motion. In comparison with a cylindrical cathode arc, the physical fields of the lamellar cathode arc are markedly expanded, leading to a reduction in current density, electron temperature, heavy particle temperature, cathode jet flow velocity, and Lorentz force.

Evaluation of Individual and Crystal Population Dissolution Rates by Time-Resolved X-ray Microtomography.

The intrinsic dissolution rate (IDR) is an important parameter in pharmaceutical science that measures the rate at which a pure crystalline active pharmaceutical ingredient dissolves in the absence of diffusion limitations. Traditional IDR measurement techniques do not capture the complex interplay between particle morphology, fluid flow, and dissolution dynamics. The dissolution rate of individual particles can differ from the population average because of factors such as particle size, surface roughness, or exposure of individual crystal facets to the dissolution medium. The aim of this work was to apply time-resolved X-ray microtomography imaging and simultaneously measure the individual dissolution characteristics of a large population of crystalline particles placed in a packed bed perfused by the dissolution medium. Using NaCl crystals in three different size fractions as a model, time-resolved microtomography made it possible to visualize the dissolution process in a custom-built flow cell. Subsequent 3D image analysis was used to evaluate changes in the shape, size, and surface area of individual particles by tracking them as they are dissolved. Information about the particle population statistics and intrabatch variability provided a deeper insight into the dissolution process that can complement established IDR measurements.

Numerical simulation of fluid-particle flow of jet in supercritical water environment

Supercritical water gasification provides a new approach to the green transformation of coal. Nevertheless, the flow characteristics of fluids and particles injected into the reactor through the nozzle still need to be further investigated. In this paper, a three-dimensional numerical simulation of the particle jet in supercritical water environment is carried out coupling Large Eddy Simulation (LES) with Discrete Phase Model (DPM). The simulation focuses on the effects of particle size, Stokes number, mass flux ratio and initial fluid velocity on the flow characteristic of the fluid-particle flow, especially on the vortex structure evolution, particle distribution and velocity profile. The findings are that as the particle size decreases and the initial fluid velocity increases, the evolution of vortex structures become increasingly fierce, such as the destruction of large-scale coherent structures, the disappearance of vortex ribs, and the lateral expansion of vortices in the development section. Particle distribution exhibits characteristics similar to the vortex structure, as particles adhere closely to the carrier fluid at low Stokes number (St < 1). On the contrary, with increasing of Stokes number (St > 1), the particles are freer from fluid interference and keep their original motion state moving forward. The fluid velocity at the center of the transverse interface jet decrease with increased mass flow ratio. For higher initial fluid velocities, particle distribution is more uniform, and more particles are carried to areas with larger radial distances.

Investigation of erosion behavior of particle-fluid flow in offshore platform T-pipes

The process of viscous oil exploitation is often accompanied by small sand particles, which harms safety production and causing consequences such as erosion. T-shaped pipes are widely used in offshore platform, and its flow protection is very important for the safe operation. This work aims to investigate the particle trajectory and erosion ratio rule in viscous oil transportation by simulation, experiment and support vector machine (SVM) model. The sensitivity analysis and the orthogonal method results demonstrate that the erosion ratio (ER) of T-pipes is proportional to the water content, gas content and sand content. And the erosion ratio (ER) of T-pipes is inversely proportional to the viscosity. The water content has the greatest effect on the pressure drop (Δp). The viscosity value around 326.79 mPa s can significantly reduce the erosion ratio while maintaining a low-pressure drop. Meanwhile, SVM model is used to calculate the erosion ratio (ER) with the mean squared error (MSE) being 4.25 × 10−6 in the training set and 0.0002 in the test set. The most severe erosion area is located in the downstream branch symmetrically. The erosion mechanisms are impact deformation and sliding, that dominate the erosion distributions.

Study on particle deposition in pipeline groove from gas–particle two-phase flow

In the process of particle–fluid flow, solid particles are easily deposited in pipes, which leads to collisions and abrasion, especially in pipelines with grooves. Therefore, some structural components are always designed above the groove to improve particle trajectories inside the groove in the pipeline. In the present study, the deposition of particles was analyzed in detail by means of experimental visualization, and Computational Fluid Dynamics and Discrete Element Method model (CFD-DEM) methods were used to investigate the motion and deposition of particles when both grooves and baffles are designed in the pipeline system. Finally, the effect of the baffle width on the deposition of particles in the groove was studied. The results show that the baffle width has a slight effect on the mass of particles deposited in the groove after the number of particles there stabilizes, but when the width of baffle is the same as that of the groove, the time it takes the particles to reach this stable state is shortest.

Innovative twist design for solar water heaters: Experimental findings and implications

More effective use of solar energy in hot water systems is made possible by optimising heat transfer and flow resistance. In light of this, Research has been conducted to enhance convective heat transfer while analysing flow friction characteristics for best performance, resulting in the design of novel inserts known as customised twists, which increase the efficiency of the solar hot water system. A conventional, plain tube heater is used as a baseline for the study on thermal characteristics, heat transportation and flow friction attributes. A thorough analysis and comparison of the thermal behaviour of the system with customised twist inserts that have been modified using rods and spacers of different lengths is performed. As a result of the induced disturbance in the fluid particle flow pattern throughout the length of risers, a significant improvement in the coefficient of convective heat transfer is observed. The study validated the correlations for the convective heat transfer coefficient and the resistance coefficient against previous research findings. The findings indicated that the thermal efficiency of the full-length twist-inserted system is almost three times greater than that of a plain collector while doubling its pressure drop. The findings of this research could be useful in designing low-cost, compact solar water heaters.

Evaluating the stability and volumetric flowback rate of proppant packs in hydraulic fractures using the lattice Boltzmann-discrete element coupling method

The stability and mobility of proppant packs in hydraulic fractures during hydrocarbon production are numerically investigated by the lattice Boltzmann-discrete element coupling method (LB-DEM). This study starts with a preliminary proppant settling test, from which a solid volume fraction of 0.575 is calibrated for the proppant pack in the fracture. In the established workflow to investigate proppant flowback, a displacement is applied to the fracture surfaces to compact the generated proppant pack as well as further mimicking proppant embedment under closure stress. When a pressure gradient is applied to drive the fluid-particle flow, a critical aperture-to-diameter ratio of 4 is observed, above which the proppant pack would collapse. The results also show that the volumetric proppant flowback rate increases quadratically with the fracture aperture, while a linear variation between the particle flux and the pressure gradient is exhibited for a fixed fracture aperture. The research outcome contributes towards an improved understanding of proppant flowback in hydraulic fractures, which also supports an optimised proppant size selection for hydraulic fracturing operations.

Influence of Thermal Slip and Ohmic Dissipation Effects on Particulate Suspension Flow through a Channel with Non-Parallel Walls

The main theme of this paper is a numerical investigation of fluid-particle flow in a channel with aslant walls (divergent channel) by taking thermal slip and Ohmic heating into account. The shooting technique with the RK-4 method is exploited to solve the system of dimensionless equations. Graphical discussions of the effects of emerging factors have been conducted for both fluid and particle aspects of temperature and velocity profiles. A perfect match is found when the current results are compared to the previous ones. The results reveal that the fluid phase temperature diminishes but particle phase temperature improves with an augmentation of the thermal slip parameter. These types of flows are used by a variety of industries, including the processing of waste water, mines, petrochemical sectors.

A micro-macro constitutive relationship for the pressure of solid phase in dense fluid-particle flows in hopper

Continuum modelling of fluid-particle multiphase flows is often challenging when the solid phase becomes dense. In this work, a micro-macro approach combining the microscale discrete element method and the averaging method is used to explore the normal stress (pressure) of the solid phase to better describe dense fluid-particle flows. Various effects of Young's modulus, Poisson ratio, sliding friction, and rolling friction are examined and an exponential relationship between pressure and solid volume fraction is proposed. With this relationship implemented, the Two-Fluid Model can reproduce the steady discharge of particles from hoppers, which is regarded as a critical test of dense particle flow for TFM. The generality of the model is tested in a variety of cases, such as different hopper angles, orifice widths and fill heights. Comparisons of the present model with previous models are also made to enhance the understandings of fluid-particle multiphase flows.

A kinetic-based model for polydisperse, high-speed, fluid–particle flows

Hyperbolic conservation equations for polydisperse, high-speed, compressible, fluid–particle flows with added mass and fluid-phase pseudoturbulence are derived. First, the kinetic-based model for monodisperse particles that accounts for collisional and frictional pressure, as well as added mass and internal energy, is reviewed. Then, a kinetic-based model for polydisperse particles is formulated in terms of the moments of the particle size distribution, and velocity moments conditioned on the particle mass or size. Transport equations for velocity moments up to second order (or total kinetic energy) are closed using the hyperbolic quadrature method of moments. In the numerical implementation for the spatial fluxes and source terms, the particle mass distribution is treated using the generalized quadrature method of moments and the size-conditioned moments are found with the conditional quadrature method of moments. Example results for spatially 1-D test cases demonstrate the ability of the polydisperse model to capture a wide range of particle-size-dependent multiphase flow physics.

Experimental study of fluid-particle flow characteristics in a rough fracture

Rough fractures can significantly affect particle-fluid flow in a stratum, but particle transport characteristics are still not fully understood. This paper proposes a novel method to combine three-dimensional laser scanning and casting technology for making rough transparent panels based on rock fractures. A large model with two-sided rough surfaces is constructed, and the inner sizes are 2 m × 0.3 m × 3 mm. The particle image velocimetry method is used to analyze slurry flow. The experimental results show that distorted irregular streamlines, vortexes, sand settling, and dispersion are primary characteristics of particles transported by low-viscosity fluid. Shear flow can induce prominent vortexes around the inlet and the fracture top. With the increase in fluid viscosity, sand-fluid flow along preferential flow paths, and particle clusters are easily formed due to sand aggregation in tortuous pathways. Increasing the fluid velocity avoids particles plugging around the inlet, and there is a threshold velocity. The vortex number has a negative relationship with fluid viscosity. With the dune accumulation, the vorticity intensity is significantly increased, and discrete vortexes are connected into a large vorticity region, which collapses sand aggregation along the whole fracture. Increasing fluid velocity and viscosity and reducing particle diameter are more effective ways to improve particle distribution than increasing particle concentration. The combination of multiple factors can enhance the more even distribution of particles in rough fractures. The investigation provides a fundamental understanding of slurry flow behaviors in fractured media and is a valuable reference for the simulation of particle-fluid flow.

Direct numerical simulation of fluid/solid particles flow inside a channel

The modeling of moving solid particles in fluid flow has been the focus of many studies and has succeeded to attract significant attention from researchers. However, commonly used modeling approaches such as discrete element modeling (DEM) and direct numerical simulations (DNS) lack simplicity and have been computationally intensive. The aim of this paper is to develop a new approach to simulate solid transport in an incompressible Newtonian fluid flow. This method is based on the Finite element method with penalization of the deformation tensor. The fluid behavior is governed by the Navier-Stokes equations within the investigation domain. To take into account collisions, we present an algorithm which allows us to handle contacts between rigid particles. In this paper, 2D fluid/particles flow simulations are performed; the results are validated by comparison with results from other methods. We attempt to simulate the conveying of solid particles behavior of circular particles in a fluid flow inside a pipe. The numerical tests show that the present method provides a very efficient approach to directly simulate the solid transport inside the channels.