scholarly journals Changes of Inertial Focusing Position in a Triangular Channel Depending on Droplet Deformability and Size

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 839
Author(s):  
Yo-han Choi ◽  
Jeong-ah Kim ◽  
Wonhee Lee
Keyword(s):  
Droplet Size ◽  
Cell Separation ◽  
Lift Force ◽  
Solid Particles ◽  
Mcf7 Cells ◽  
Inertial Focusing ◽  
Threshold Size ◽  
Triangular Channel ◽  
And Shifts ◽  
Viscous Droplets

Studies on cell separation with inertial microfluidics are often carried out with solid particles initially. When this condition is applied for actual cell separations, the efficiency typically becomes lower because of the polydispersity and deformability of cells. Therefore, the understanding of deformability-induced lift force is essential to achieve highly efficient cell separation. We investigate the inertial focusing positions of viscous droplets in a triangular channel while varying Re, deformability, and droplet size. With increasing Re and decreasing droplet size, the top focusing position splits and shifts along the sidewalls. The threshold size of the focusing position splitting increases for droplets with larger deformability. The overall path of the focusing position shifts with increasing Re also has a strong dependency on deformability. Consequently, droplets of the same size can have different focusing positions depending on their deformability. The feasibility of deformability-based cell separation is shown by different focusing positions of MCF10a and MCF7 cells.

scholarly journals Inertial focusing of finite-size particles in microchannels

2018 ◽  
Vol 840 ◽  
pp. 613-630 ◽  
Author(s):  
Evgeny S. Asmolov ◽  
Alexander L. Dubov ◽  
Tatiana V. Nizkaya ◽  
Jens Harting ◽  
Olga I. Vinogradova
Keyword(s):  
Lattice Boltzmann ◽  
Slip Velocity ◽  
Lift Force ◽  
Finite Size ◽  
Reynolds Numbers ◽  
Velocity Difference ◽  
Inertial Focusing ◽  
Inertial Migration ◽  
Lattice Boltzmann Simulations ◽  
Insight Into

At finite Reynolds numbers, $Re$, particles migrate across laminar flow streamlines to their equilibrium positions in microchannels. This migration is attributed to a lift force, and the balance between this lift and gravity determines the location of particles in channels. Here we demonstrate that velocity of finite-size particles located near a channel wall differs significantly from that of an undisturbed flow, and that their equilibrium position depends on this, referred to as slip velocity, difference. We then present theoretical arguments, which allow us to generalize expressions for a lift force, originally suggested for some limiting cases and $Re\ll 1$, to finite-size particles in a channel flow at $Re\leqslant 20$. Our theoretical model, validated by lattice Boltzmann simulations, provides considerable insight into inertial migration of finite-size particles in a microchannel and suggests some novel microfluidic approaches to separate them by size or density at a moderate $Re$.

Assessing the Effects of Near Wall Corrections of the Force Acting on Particles in Gas-Solid Channel Flows

2005 ◽  
Author(s):  
Boris Arcen ◽  
Anne Tanie`re ◽  
Benoiˆt Oesterle´
Keyword(s):  
Channel Flow ◽  
Lift Force ◽  
Particle Concentration ◽  
Turbulent Channel Flow ◽  
Shear Velocity ◽  
Solid Particles ◽  
Wall Region ◽  
Wall Effects ◽  
Strong Shear ◽  
Near Wall

The importance of using the lift force and wall-corrections of the drag coefficient for modeling the motion of solid particles in a fully-developed channel flow is investigated by means of direct numerical simulation (DNS). The turbulent channel flow is computed at a Reynolds number based on the wall-shear velocity and channel half-width of 185. Contrary to most of the numerical simulations, we consider in the present study a lift force formulation that accounts for the weak and strong shear as well as for the wall effects (hereinafter referred to as optimum lift force), and the wall-corrections of the drag force. The DNS results show that the optimum lift force and the wall-corrections of the drag together have little influence on most of the statistics (particle concentration, mean velocities, and mean relative and drift velocities), even in the near wall region.

scholarly journals Effect of Solid Particles on Droplet Size Applying the Time-Shift Method for Spray Investigation

2020 ◽  
Vol 10 (21) ◽  
pp. 7615
Author(s):  
Simon Wachter ◽  
Tobias Jakobs ◽  
Thomas Kolb
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Solid Particles ◽  
Time Shift ◽  
Pure Liquid ◽  
Sauter Mean Diameter ◽  
Shift Method ◽  
Spray Formation ◽  
Primary Breakup ◽  
Shift Effect

This study investigated the influence of solid particles on primary breakup and resulting droplet size for different process parameters. Two sets of Newtonian fluids (each consisting of one pure liquid and one suspension at the same respective viscosity) were used, for isolated investigation of solid particles on spray formation independent of liquid viscosity. The spray was recorded by a high-speed camera and a SpraySpy® system based on the time-shift effect, while a commonly used Spraytec® laser diffraction analyzer was employed for validation. An external-mixing twin-fluid atomizer was operated at different gas velocities and corresponding GLR at constant liquid mass flow. For the investigated suspensions an increased Sauter mean diameter was detected, compared to the pure liquids with identical dynamic viscosity. This effect was explained by the tensile strength stabilizing the suspension droplets.

Pipe-Wall Friction in Vertical Sand-Slurry Flows

2005 ◽  
Author(s):  
Vaclav Matousek
Keyword(s):  
Lift Force ◽  
Pipe Wall ◽  
Fine Sand ◽  
Coarse Sand ◽  
Solid Particles ◽  
Wall Friction ◽  
Wall Region ◽  
Pressure Drops ◽  
Frictional Pressure Drop ◽  
Near Wall

Friction due to the presence of solid particles suspended in a flow is a result of processes in a relatively thin layer near the pipe wall. Pipe-wall friction generated by particles in permanent contact with pipe wall is relatively well understood. However, very little is known about the friction deriving from sporadic contact (collisions) of particles with the wall. This friction is a major contributor to the frictional pressure drop in many slurry pipeline applications. The paper describes results of extensive laboratory tests of vertical flows of different sand fractions (fine, medium and coarse sands) carried out in the Laboratory of Dredging Engineering of the Delft University. In order to identify mechanisms that govern the solid-particle friction at the pipe wall the paper analyses friction conditions in observed vertical flows. The effects of particle-particle interactions and particle-liquid interactions on the pipe-wall friction are evaluated. One of the interesting phenomena observed in the laboratory was that frictional pressure drops in highly-concentrated flows at high velocities are lower for slurries of medium sand and coarse sand than for slurries of fine sand. The observed trend is believed to be associated with the liquid–lift force acting on solid particles traveling near a pipe wall. This off-wall force seems to be the most effective for medium to coarse particles traveling in highly concentrated mixture in the near-wall region. Thus pressure drops due to the presence of solids in non-stratified flows seem to be primarily produced by the combined effect of the Bagnold collisional force (force that colliding particles exert against the pipe wall) and liquid lift force acting on solid particles in the near-wall zone of the slurry flow.

High-throughput particle focusing and separation in split-recombination channel

2022 ◽  
Vol 32 (2) ◽  
pp. 025007
Author(s):  
Shuang Chen ◽  
Zongqian Shi ◽  
Jiajia Sun ◽  
Shenli Jia ◽  
Mingjie Zhong ◽  
...  
Keyword(s):  
High Throughput ◽  
Lift Force ◽  
Curvature Radius ◽  
Straight Channel ◽  
Geometrical Structures ◽  
Inertial Focusing ◽  
Particle Focusing ◽  
Drag Forces ◽  
Recombination Channel ◽  
Flow Drag

Abstract Inertial microfluidic has been widely applied to manipulate particles or bio-sample based on the inertial lift force and Dean Vortices. This technology provides significant advantages over conventional technologies, including simple structure, high throughput and freedom from an external field. Among many inertial microfluidic systems, the straight microchannel is commonly used to produce inertial focusing, which is a phenomenon that particles or cells are aligned and separated based on their size under the influence of inertial lift force. Besides the inertial lift force, flow drag forces induced by the geometrical structures of microchannel can also affect particle focusing. Herein, a split-recombination microchannel, consisting of curved and straight channels, is proposed to focus and separate particles at high flow rate. As compared with the straight channel, the particle focusing in the split-recombination channel is greatly improved, which results from the combined effects of the inertial lift force, the curvature-induced Dean drag force and the structure of split and recombination. Moreover, the distribution of different-sized particles in designed microchannel is investigated. The results indicate that the proposed microchannel not only enhances the particle focusing but also enables the separation of different-sized particles with high throughput. Finally, it is discovered that the larger length of straight channel and curvature radius of curved channel can result in a more efficient particle separation. Another important feature of designed split-recombination microchannel is that it can be arranged in parallel to handle large-volume samples, holding great potential in lab-on-a-chip applications.

Impulsive Motion in a Particle-Fluid Suspension Including Particulate Volume, Density, and Migration Effects

1974 ◽  
Vol 41 (1) ◽  
pp. 35-41 ◽  
Author(s):  
P. R. Di Giovanni ◽  
S. L. Lee
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Lift Force ◽  
Interaction Force ◽  
Volume Density ◽  
Solid Particles ◽  
Impulsive Motion ◽  
Viscous Boundary Layer ◽  
Small Times ◽  
Particulate Volume

Based on expansions for small and large times, velocity and particulate volume distributions are obtained from the approximate continuum representation of a suspension of uniformly distributed small spherical solid particles for flow induced by impulsive motion of an infinite flat plate. Included in the analysis are major effects of the fractional particulate volume, which is assumed to vary due to the inclusion of the particle slip-shear lift force, as well as a generalized drag interaction force. For both small and large times, the lift force results in an accumulation of particles near the wall. Motion in the horizontal direction is determined in terms of modified similarity variables for large and small times indicating an increase or decrease in the viscous boundary layer for small times depending on the fractional volume of particles, and an increase or decrease for large times depending on whether the particles are lighter or heavier than the fluid. To the zeroth order, the skin friction on the wall is shown to increase or decrease for small times depending on whether the ambient fractional particulate volume is greater or less than 1/4. For large times the friction increases for heavy particles and decreases for light particles. Finally, by using the modified Rayleigh’s method, an estimate is made for boundary-layer flow past a semi-infinite flat plate.

scholarly journals Pattern Transition on Inertial Focusing of Neutrally Buoyant Particles Suspended in Rectangular Duct Flows

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1242
Author(s):  
Hiroshi Yamashita ◽  
Takeshi Akinaga ◽  
Masako Sugihara-Seki
Keyword(s):  
Cross Section ◽  
Lift Force ◽  
Pitchfork Bifurcation ◽  
Blockage Ratio ◽  
Duct Flow ◽  
Rectangular Duct ◽  
Inertial Focusing ◽  
Particle Focusing ◽  
Wide Range ◽  
The Cross

The continuous separation and filtration of particles immersed in fluid flows are important interests in various applications. Although the inertial focusing of particles suspended in a duct flow is promising in microfluidics, predicting the focusing positions depending on the parameters, such as the shape of the duct cross-section and the Reynolds number (Re) has not been achieved owing to the diversity of the inertial-focusing phenomena. In this study, we aimed to elucidate the variation of the inertial focusing depending on Re in rectangular duct flows. We performed a numerical simulation of the lift force exerted on a spherical particle flowing in a rectangular duct and determined the lift-force map within the duct cross-section over a wide range of Re. We estimated the particle trajectories based on the lift map and Stokes drag, and identified the particle-focusing points appeared in the cross-section. For an aspect ratio of the duct cross-section of 2, we found that the blockage ratio changes transition structure of particle focusing. For blockage ratios smaller than 0.3, particles focus near the centres of the long sides of the cross-section at low Re and near the centres of both the long and short sides at relatively higher Re. This transition is expressed as a subcritical pitchfork bifurcation. For blockage ratio larger than 0.3, another focusing pattern appears between these two focusing regimes, where particles are focused on the centres of the long sides and at intermediate positions near the corners. Thus, there are three regimes; the transition between adjacent regimes at lower Re is found to be expressed as a saddle-node bifurcation and the other transition as a supercritical pitchfork bifurcation.

Comparing Simulation for Turbulent Dispersion and Coalescence of Droplets within a Spray with Two Models

2013 ◽  
Vol 353-356 ◽  
pp. 2473-2476
Author(s):  
Shao Yun Deng
Keyword(s):  
Droplet Size ◽  
Droplet Size Distribution ◽  
Computer Time ◽  
Turbulent Dispersion ◽  
Gas Flows ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Time Required ◽  
And Shifts ◽  
Droplet Size Distributions

Lagrangian and Eulerian modelling approaches are compared for simulating turbulent dispersion and coalescence of droplets within a spray. Both models predict similar droplet dispersion rates and shifts in droplet size distribution due to coalescence within the spray, over a wide range of droplet and gas flows, and for sprays with different droplet size distributions at the nozzle exit. The computer time required for simulating coalescence within a steady axisymmetric spray is of a similar order of magnitude regardless of which formulation, Eulerian or Lagrangian, is adopted. However, the Lagrangian formulation is more practical in terms of the range of applicability and ease of implementation.

scholarly journals The upper limit and lift force within inertial focusing in high aspect ratio curved microfluidics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Javier Cruz ◽  
Klas Hjort
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Lift Force ◽  
Complex Fluids ◽  
Scaling Law ◽  
Valuable Insight ◽  
High Quality ◽  
Inertial Focusing ◽  
Upper Limit ◽  
Insight Into

AbstractMicrofluidics exploiting the phenomenon of inertial focusing have attracted much attention in the last decade as they provide the means to facilitate the detection and analysis of rare particles of interest in complex fluids such as blood and natural water. Although many interesting applications have been demonstrated, the systems remain difficult to engineer. A recently presented line of the technology, inertial focusing in High Aspect Ratio Curved microfluidics, has the potential to change this and make the benefits of inertial focusing more accessible to the community. In this paper, with experimental evidence and fluid simulations, we provide the two necessary equations to design the systems and successfully focus the targets in a single, stable, and high-quality position. The experiments also revealed an interesting scaling law of the lift force, which we believe provides a valuable insight into the phenomenon of inertial focusing.

DESIGN, SIMULATION AND COMPARISON OF ASCENDING AND DESCENDING CURVILINEAR MICROCHANNELS FOR CANCER CELL SEPARATION FROM BLOOD

2013 ◽  
Vol 25 (03) ◽  
pp. 1350037 ◽  
Author(s):  
W. A. H. S. S. Wewala ◽  
Jafar Khan Kasi ◽  
Ajab Khan Kasi ◽  
Nitin Afzulpurkar
Keyword(s):  
Blood Cell ◽  
Cancer Cells ◽  
Cell Separation ◽  
Disease Monitoring ◽  
Potential Importance ◽  
Inertial Focusing ◽  
Curvilinear Channel ◽  
Computational Fluid Dynamics Cfd ◽  
Rare Cells ◽  
Two Stages

Separation of rare cells such as circulating cancer and fetal cells from blood has potential importance in disease monitoring and prevention. In this paper, we report a new method of cancer cells separation from patient blood by inertial focusing technique. A design and simulation of ascending and descending curvilinear microchannels for separation of particles resembling cancer cells have been presented. In simulation, polystyrene particles have been used which represent the size of red blood cell (RBC), white blood cell (WBC) and cancer cells. Computational fluid dynamics (CFD) design and simulation of ascending and descending microchannels is used for cell separation. The simulation was carried out in two stages including focusing and separation. The ascending curvilinear channel design demonstrated favorable focusing and separation. Separation with 100% purity and efficiency of the unwanted particle was achieved at Reynolds number (Re) = 8.50 and velocity 0.105 m/s. In case of descending curvilinear channel, cell separation was not good. Considering cancer cells size about 15 μm, our proposed ascending microchannel is a good candidate for cancer cells separation from blood.

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