Fluid Particle Separation Research Articles

Comparative Studies of Experimental and Numerical Investigations of Fluid Flow and Particle Separation of High-Gravity Spiral Concentrators

Comparative Studies of Experimental and Numerical Investigations of Fluid Flow and Particle Separation of High-Gravity Spiral Concentrators

Solute-particle separation in microfluidics enhanced by symmetrical convection.

The utilization of microfluidic technology for miniaturized and efficient particle sorting holds significant importance in fields such as biology, chemistry, and healthcare. Passive separation methods, achieved by modifying the geometric shapes of microchannels, enable gentle and straightforward enrichment and separation of particles. Building upon previous discussions regarding the effects of column arrays on fluid flow and particle separation within microchips, we introduced a column array structure into an H-shaped microfluidic chip. It was observed that this structure enhanced mass transfer between two fluids while simultaneously intercepting particles within one fluid, satisfying the requirements for particle interception. This enhancement was primarily achieved by transforming the originally single-mode diffusion-based mass transfer into dual-mode diffusion-convection mass transfer. By further optimizing the column array, it was possible to meet the basic requirements of mass transfer and particle interception with fewer microcolumns, thereby reducing device pressure drop and facilitating the realization of parallel and high-throughput microfluidic devices. These findings have enhanced the potential application of microfluidic systems in clinical and chemical engineering domains.

Optimizing Rapid Prototype Development Through Femtosecond Laser Ablation and Finite Element Method Simulation for Enhanced Separation in Microfluidics

In recent years, microfluidic systems have emerged as promising tools for blood separation and analysis. However, conventional methods for prototyping microfluidic systems can be slow and expensive. In this study, we present a novel approach to rapid prototyping that combines femtosecond laser ablation and finite element method (FEM) simulation. The optimization of the prototyping process was achieved through systematic characterization of the laser ablation process and the application of FEM simulation to predict the flow behavior of the microfluidic devices. Using a dean-coupled inertial flow device (DCIFD) that comprises one channel bend and three outlets side-channels. DCIF is a phenomenon that occurs in curved microfluidic channels and is considered by the existence of inconsequential flow patterns perpendicular to the main flow direction. The DCIF can enhance the separation efficiency in microfluidic devices by inducing lateral migration of particles or cells towards specific locations along the channel. This lateral migration can be controlled by adjusting the curvature and dimensions of the channel, as well as the flow rate and properties of the fluid. Overall, DCIF can provide a valuable means of achieving efficient and high-throughput separation of particles or cells in microfluidic devices. Therefore, various microfluidics designs that contain different outlet channels were studied in this research to improve blood plasma separation efficiency. Results from imitated blood flow experiments showed positive results for fluid flow and particle separation. The study also found that incorporating three various channel widths is the key to achieving efficient plasma separation, indicating that this result could serve as a guideline for future microfluidics geometry specifications in the field of blood plasma separation. According to the FEM simulation, the highest separation percentage for both microparticle sizes was obtained by incorporating a variable outlet channel width into the same microfluidic device. The FEM simulation revealed that around 95% of the larger microparticles separated while 98% of the smaller microparticles separated. This is consistent with the imitated blood separation results, which showed that 91% of the larger microparticles separated and around 93% of the smaller microparticles were separated. Overall, our results demonstrate that the combination of femtosecond laser ablation and FEM simulation significantly improved the prototyping speed and efficiency while maintaining high blood separation performance.

CFD-DEM analysis of internal packing structure and pressure characteristics in compressible filter cakes using a novel elastic–plastic contact model

Cake-forming filtration is a proven method for separating particles from suspensions. Most filtration models are based on the simplification of incompressible and homogeneous cake structures. However, most filter cakes are in fact unevenly compressed by e.g. the high transmembrane pressures, leading to dense structures with high flow resistance at the filtration membrane. Experimental investigations of these inhomogeneous cakes are challenging due to mostly invasive procedures after filtration has already taken place. In contrast, numerical methods can provide extensive information about fluid flow, particle separation and cake formation during filtration. However, this requires that both elastic and plastic particle deformation and forces are modeled correctly. To achieve this, the present study implemented a novel elastic–plastic DEM model that only requires measurable material parameters and therefore does not need any fitting. Subsequently, previously measured material parameters for elastic–plastic cellulose-lactose pellets (MCC) were used to investigate the packing density, fluid pressure levels and contact forces inside compressible filter cakes using CFD-DEM coupling. A comparison with incompressible and elastically compressible filter cakes showed a significant difference in the filtration behavior. Due to plastic deformation, a strong increase of the packing density when nearing the filtration membrane was found, leading to higher flow resistance for the filtration process. For cyclic filtration events, only the plastically deformed cake showed reduced height recovery in a relaxed state.

Novel Approaches Concerning the Numerical Modeling of Particle and Cell Separation in Microchannels: A Review

The demand for precise separation of particles, cells, and other biological matter has significantly increased in recent years, leading to heightened scientific interest in this topic. More recently, due to advances in computational techniques and hardware, numerical simulations have been used to guide the design of separation devices. In this article, we establish the theoretical basis governing fluid flow and particle separation and then summarize the computational work performed in the field of particle and cell separation in the last five years with an emphasis on magnetic, dielectric, and acoustic methods. Nearly 70 articles are being reviewed and categorized depending on the type of material separated, fluid medium, software used, and experimental validation, with a brief description of some of the most notable results. Finally, further conclusions, future guidelines, and suggestions for potential improvement are highlighted.

Objective barriers to the transport of dynamically active vector fields

Abstract

Three-Dimensional Numerical Simulation of Particle Focusing and Separation in Viscoelastic Fluids.

Particle focusing and separation using viscoelastic microfluidic technology have attracted lots of attention in many applications. In this paper, a three-dimensional lattice Boltzmann method (LBM) coupled with the immersed boundary method (IBM) is employed to study the focusing and separation of particles in viscoelastic fluid. In this method, the viscoelastic fluid is simulated by the LBM with two sets of distribution functions and the fluid–particle interaction is calculated by the IBM. The performance of particle focusing under different microchannel aspect ratios (AR) is explored and the focusing equilibrium positions of the particles with various elasticity numbers and particle diameters are compared to illustrate the mechanism of particle focusing and separation in viscoelastic fluids. The results indicate that, for particle focusing in the square channel (AR = 1), the centerline single focusing becomes a bistable focusing at the centerline and corners as El increases. In the rectangular channels (AR < 1), particles with different diameters have different equilibrium positions. The equilibrium position of large particles is closer to the wall, and large particles have a faster lateral migration speed and few large particles migrate towards the channel center. Compared with the square channel, the rectangular channel is a better design for particle separation.

Axial acoustic field barrier for fluidic particle manipulation

An acoustic field barrier integrated within a flow tubing system to achieve high-throughput separation of particles in fluid is reported in this work. We investigate the axial acoustic field of a piezo-tube with an inside diameter of 34 mm, a length of 25 mm, and an operating frequency of 1.15 MHz. Energy concentrates within the tube, and leakage at the ends provides a sharp monotonic acoustic pressure field within a fluidic circuit. This process is not the conventional standing wave mechanism; instead, the geometry produces a spatially stable filtering action without fouling. This powerful filtering action is confirmed theoretically via a COMSOL simulation and demonstrated experimentally by concentrating suspensions of 5 μm proteoglycan tracer particles at a flow rate of 20 ml/min: The corresponding acoustic contrast factor is 0.243, and the trapping force is 11pN. This tube geometry tackles the limitations of microfluidic standing wave based acoustic concentrators, namely, complex extraction, low-throughput, and distributed focus, by harnessing a stable monotonic field profile.

Study on the stability of a shear-thinning suspension used in oil well drilling

In order to avoid solid-liquid gravitational separation of particles in the drilling fluid and cuttings generated in this process, the oil industry has been developing drilling fluids with shear-thinning and thixotropic characteristics. In case of operational stops in the drilling process, the intense sedimentation of these particles can damage the equipment used and the well. In this context, this study simulated an operational stop to obtain information about stability of solids in a paraffin-based suspension with time-dependent shear-thinning behavior, which has already been used in current drilling processes. A long-term test using gamma-ray attenuation technique identified the separation dynamics of a set of micrometric particles belonging to and incorporated into the drilling fluid during operation. This test verified the typical regions of gravitational sedimentation and, through constant concentration curves, indicated that the sedimentation process did not occur at a constant rate. This study also proposed a constitutive equation for pressure on solids.

Effectiveness of a hydrocyclone in separating particles suspended in power law fluids

This study evaluated the separation of particles suspended in power law fluids by applying a 10mm hydrocyclone. Al2O3 particles were added to an aqueous polyacrylic acid solution to prepare 0.1vol% suspensions with different flow behaviors. The effects of operating conditions, such as the inlet velocity, pressure drop, split ratio, and fluid flow behavior, on the fluid velocity distribution, particle trajectory, and particle separation efficiency were studied. The study applied a simulation in which the governing equations were coupled using the SIMPLE algorithm; the Reynolds stress model served as a turbulence model. The distributions of the fluid velocity and pressure were simulated using a segregated, steady-state, three-dimensional implicit numerical solver provided by ANSYS 15.0 software. The tangential velocity increased with the flow behavior index, n, at a fixed inlet velocity and split ratio. This effect was attributed to a lower molecular viscosity. The particle trajectories were simulated using a Lagrangian frame. The particle migration in the cylindrical part of the hydrocyclone dominated the particle separation efficiency. A reduction in the fluid n-value engendered a higher effective viscosity and lower tangential velocity, which caused fewer particle rotations and lower centrifugal effects, consequently lowering the opportunity for particles to collect in the underflow. The separation efficiency increased with the inlet velocity and particle size because of a higher centrifugal effect, but the influence of the inlet velocity was extremely small for a low fluid n-value. The total separation efficiency increased by approximately 40% as the n-value increased from 0.51 to 1.00. The simulated particle separation efficiency was highly consistent with experimental data. This verified the reliability of the simulation method and the validity of this method for understanding the effects of fluid flow behavior on particle separation performance.

Towards efficient surface acoustic wave (SAW)-based microfluidic actuators

The applicability of surface acoustic wave (SAW) based actuators was demonstrated for a variety of microfluidic tasks, including fluid mixing, particle separation, localized heating or fluid atomization. But as traditionally the main field of application lies in high-frequency telecommunication, SAW devices are only marginally optimized for microfluidics, especially in respect to an energy efficient operation. In lab setups incorporating SAW-based microfluidic actuators, insufficient energy efficiency resulting e.g. from interdigital transducers (IDTs) with inadequate electrical impedance, absorption of SAW power in vessel walls or maladjusted wavelengths, is often simply counteracted by an increase of the output power of the signal source. For the operation of portable or highly integrated devices, though, or for devices with high power needs, energy efficiency is crucial. Additionally, an inefficient mode of operation can result in severe device degradation.In order to extend the performance of SAW actuators, we discuss different approaches regarding the optimization of their power efficiency and provide selected experimental results, highlighting the importance of the governing power loss effects. Depending on the intended microfluidic task, several of the demonstrated optimization strategies can be combined and – as will be shown – considerable improvements in the device performance can be achieved.

Hydrodynamic chromatography using flow of a highly concentrated dextran solution through a coiled tube

Separation of colloidal particles in non-Newtonian fluid is important in food engineering. Using hydrodynamic chromatography, colloidal particles and starch granules originating from corn were individually injected into dextran solutions (Mw 2,000,000g/mol) flowing through a coiled tube for efficient size separation. Rheological properties of dextran solutions ranging from 50 to 250g/L were determined, revealing pseudoplastic fluid behavior. Velocity profiles for dextran solution flow in coiled tubes were obtained from rheological power law parameters. Suspensions of colloidal particles of diameters 1.0 and 20μm were individually injected into the dextran flows, demonstrating that dextran solutions at high concentration separated colloidal particles. Starch granules were separated by size using a dextran solution flow (250g/L). Thus, we expect to obtain efficient separation of colloidal particles in foods using highly concentrated dextran solutions.

Magneto-rheological defects and failures: A review

Magneto-rheological fluid is the colloidal suspension of micron sized magnetic particles in a carrier fluid where defects and failures occur at many circumstances. This paper presents a review on defects and failures of magneto-rheological fluid in engineering applications. The most significant defect is hard cake which developed due to re-dispersion difficulties of remnant particles magnetization, leaving the magneto-rheological fluid ineffective. Clumping effect on the other hand is a separation of carrier fluid from the magnetic particles when magneto-rheological fluid is being exposed to higher magnetic field for an extended period of time. As clumping occurred, it leads to Fluid Particle Separation (FPS) which is believed altering the strength distribution of magneto-rheological fluid and therefore reducing the squeezing force. Another significant failure is magnetic particles oxidation of the magneto-rheological fluid. This paper also will discuss on stability problems which is the most challenged issue in magneto-rheological fluid technology. With the comprehensive review in this paper, researcher can design materials of magneto-rheological fluid for better properties.

A Three-Step Scenario Involved in Particle Capture on a Pore Edge

A scenario is proposed to describe the capture of a spherical particle around a cylindrical pore. This geometry, "ideal" as far as the problem of particle capture on a filtration membrane is concerned, is clearly relevant in view of the pore-scale geometry of nucleopore or microsieve filtration membranes, and also of some microfluidic systems used to perform fluid-particle separation. The present scenario consists of three successive steps: particle deposition on the membrane away from the pore, subsequent reentrainment of some of the deposited particles by rolling on the membrane surface, and final arrest by a stabilizing van der Waals torque when the particle rolls over the pore edge. A modeling of these three steps requires the hydrodynamic and physicochemical particle-membrane interactions to be detailed close to the singular pore edge region and raises questions concerning the role of particle surface roughness. The relevance and robustness of such of a scenario for rough micrometer-sized latex particles is emphasized and comparisons are made with existing experimental data.

Fluid-Particle Separation of Magnetorheological (MR) Fluid in MR Machining Application

The presented work is an investigation of fluid-particle separation phenomena and compression stress resistance performance of magnetorheological (MR) fluids under squeeze mode. The squeeze mode is very significant to MR machining application. Material used in this study was silicone oil based MR fluid with 20% volume fraction of carbonyl iron particle. Compression test was performed by integrating the developed squeeze mode testing rig with a 50 kN Universal Testing Machine (UTM). The tests were conducted at constant speed and current. Each test was conducted at an initial gap of 2 mm and was stopped at a final gap of 0.5 mm. Force-displacement data was recorded and was analysed using TestExpert® II software. Full factorials with 27 experiments were designed using Design Expert 7 software. Three factors investigated in the design of experiments were carrier fluid viscosity, supplied current, and compression speed. Responses measured were strain energy and compression stress at maximum strain. Macro images of the phenomenon were recorded and evaluated qualitatively. From the compression stress-strain results, carrier fluid viscosity was significant to vary the MR fluid properties. The observed phenomenon shows that fluid-particle separation occurred in the low viscosity carrier fluid, low compression speed and high applied current. The parameters effect on strain energy and compression stress suggests that the fluid-particle separation is significant to the squeeze mode MR fluid performance. The relationship between stress resistance performance and fluid-particle separation phenomena were significant in designing innovative MR fluid devices.

Performance comparison of a single and triple tangential inlet gas separation cyclone: A CFD Study

Abstract Separating particulates from blast furnace top gas can pose a significant challenge to process industries. As a result, the correct decision must be made to economically and productively extract dust from the top gas flow. The primary separation phase of a blast furnace gas cleaning plant can use a gravity dust-catcher, but increasingly, gas cyclone separators are being used due to their superior cleaning abilities and markedly enhanced efficiency. Flow patterns within cyclone separators are complex due to the anisotropic nature of such systems, making it difficult to accurately predict fluid and particle performance. Two cyclone configurations are considered, a single and triple inlet, to see if cyclone performance can be improved with different inlet section configurations. The fluid flow profile and particle separation efficiency performance subjected to a specific flue dust distribution is analysed. CFD simulations using the RSM turbulence model in ANSYS Fluent v.13 are undertaken. It is concluded that the triple inlet cyclone configuration is the better solution due to lower pressure drop, near identical efficiency performance to the single inlet configuration, and the potential for reduced wear rates as a result of lower inlet and rotational flow velocities in the cyclone body, whilst still maintaining a stable vortex air core.

The separation mechanism and application of a tapered diameter separation bed

Research on recycling waste printed circuit boards is at the forefront of preventing environmental pollution and finding ways to recycle resources. A wet process for reclaiming metals from printed circuit boards applying a tapered diameter separation bed is described, and the separation mechanism of the device is proposed. The motion of a particle in the tapered diameter fluid flow field and particle separation within this field were studied. As the material passes through the fluid field, along with the water, differences in particle density, granularity, and shape cause particles to follow at different trajectories. A tapered diameter separation bed was used to process 1–0.074 mm-sized crushed material from discarded printed circuit boards. The separation efficiency of 91.77 % and the recovery rate of 95.79 % for recovered metal were achieved with a discharge water flow rate of 4.5m3/h, a material feed rate of 300 g/min, and an obliquity of 30°. For −0.074 mm printed circuit boards, the metal recovery is 93.42 % and the separation efficiency is 77.63 % when the water discharge is 2 m3/h, the obliquity is 35o, and the material feed rate is 450 g/min. The superfine products in a size range of −0.074 mm can be recovered effectively under suitable operating condition using the tapered diameter separation bed. It indicates that the lower separation limit of the tapered diameter separation bed can be close to zero. The technique will prevent environmental pollution from waste printed circuit boards and allow efficient recovery.

Computational study of the flow characteristics and separation efficiency in a mini-hydrocyclone

The development of a simple and feasible fluid–solid separation device is critical to further advancement in the use of micro-technology. The mini-hydrocyclone, which possesses a concise geometry and simple operational process, has been proposed as a promising solution to bridge this gap since the cut-size decreases with decreasing hydrocyclone diameter. In this work, we investigated the fluid flow and particle separation ability of a 5mm diameter mini-hydrocyclone through computational fluid dynamics (CFD) modelling. Direct numerical simulation (DNS) results with CFD have shown that the flow transition and subsequent unsteady state behaviour occurred in the mini-hydrocyclone at a low Reynolds number (Rein=300) because of the onset of centrifugal instability. The centrifugal instability offered an insight into the flow transition and the development of turbulent flow in hydrocyclones which have not been studied. The centrifugal instability in the mini-hydrocyclone begins as Görtler vortices developing in the boundary layer and they subsequently affect the flow field. Particle motion tracing showed that improved separation with finer cut size, d50, and steeper separation sharpness were obtained as the inlet velocity was increased. The improvement can be explained by the flow characteristics when the flow transits to turbulent flow.

Fluid–Particle Separation of Magnetorheological Fluid in Squeeze Mode

In squeeze mode, magnetorheological (MR) fluids exhibit a unique behaviour when compression load is applied. The MR fluids were assumed to experience fluid–particle separation phenomenon, where magnetic particles and carrier fluid were separated at some extent of compression. In this study, the establishment of this phenomenon has been carried out. A cyclic compression test was performed on hydrocarbon-based MR fluid, where a video camera was used to record the expelling fluid. Solidified samples of epoxy-based MR fluid were then prepared and the cured samples were sectioned, mounted and prepared for metallographic study. Images extracted from the recorded video have shown that there was a separation of carrier fluid during compression where a brighter colour of fluid was observed expelling from the testing region. Furthermore, analyses of the micrographs demonstrated the increment of the particle distribution along compression process. The separation process was responsible for the variability of particle volume fraction in order to achieve desirable stresses.

Separating impact on an elliptic cylinder floating on the surface of an ideal incompressible finite-depth fluid

The method of nonlinear integral equations of the Hammerstein type is applied to numerically analyze the problem of the separating impact on an elliptic cylinder floating on the surface of an ideal incompressible finite-depth fluid. The bottom effect and the influence of the kinematic and geometric parameters on the zone of fluid particle separation from the cylinder surface are studied.