scholarly journals Strategic placement of an obstacle suppresses droplet break up in the hopper flow of a microfluidic soft crystal

2021 ◽  
Vol 118 (19) ◽  
pp. e2017822118
Author(s):  
Alison D. Bick ◽  
Jian Wei Khor ◽  
Ya Gai ◽  
Sindy K. Y. Tang
Keyword(s):  
Particle System ◽  
Three Dimensional ◽  
Colloidal Suspensions ◽  
Hopper Flow ◽  
Geometrical Constraints ◽  
Emulsion Drops ◽  
Break Up ◽  
Interparticle Friction ◽  
Soft Crystal ◽  
Fast Flow

When granular materials, colloidal suspensions, and even animals and crowds exit through a narrow outlet, clogs can form spontaneously when multiple particles or entities attempt to exit simultaneously, thereby obstructing the outlet and ultimately halting the flow. Counterintuitively, the presence of an obstacle upstream of the outlet has been found to suppress clog formation. For soft particles such as emulsion drops, clogging has not been observed in the fast flow limit due to their deformability and vanishing interparticle friction. Instead, they pinch off each other and undergo break up when multiple drops attempt to exit simultaneously. Similar to how an obstacle reduces clogging in a rigid particle system, we hypothesize and demonstrate that an obstacle could suppress break up in the two-dimensional hopper flow of a microfluidic crystal consisting of dense emulsion drops by preventing the simultaneous exit of multiple drops. A regime map plotting the fraction of drops that undergo break up in a channel with different obstacle sizes and locations delineates the geometrical constraints necessary for effective break up suppression. When optimally placed, the obstacle induced an unexpected ordering of the drops, causing them to alternate and exit the outlet one at a time. Droplet break up is suppressed drastically by almost three orders of magnitude compared to when the obstacle is absent. This result can provide a simple, passive strategy to prevent droplet break up and can find use in improving the robustness and integrity of droplet microfluidic biochemical assays as well as in extrusion-based three-dimensional printing of emulsion or foam-based materials.

Three-dimensional simulation of primary break-up in a close-coupled atomizer

2012 ◽  
Vol 108 (4) ◽  
pp. 783-792 ◽  
Author(s):  
N. Zeoli ◽  
H. Tabbara ◽  
S. Gu
Keyword(s):  
Three Dimensional ◽  
Break Up ◽  
Dimensional Simulation ◽  
Primary Break

Dielectrophoretic Mixing With Novel Electrode Geometry

2009 ◽  
Author(s):  
G. Naga Siva Kumar ◽  
Sushanta K. Mitra ◽  
Subir Bhattacharjee
Keyword(s):  
Electric Field ◽  
Cell Activation ◽  
Colloidal Particles ◽  
Colloidal Suspension ◽  
Three Dimensional ◽  
Colloidal Suspensions ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Computational Domain ◽  
Element Analysis

Electrokinetic mixing of analytes at micro-scale is important in several biochemical applications like cell activation, DNA hybridization, protein folding, immunoassays and enzyme reactions. This paper deals with the modeling and numerical simulation of micromixing of two different types of colloidal suspensions based on principle of dielectrophoresis (DEP). A mathematical model is developed based on Laplace, Navier-Stokes, and convection-diffusion-migration equations to calculate electric field, velocity, and concentration distributions, respectively. Mixing of two colloidal suspensions is simulated in a three-dimensional computational domain using finite element analysis considering dielectrophoretic, gravitational and convective (advective)–diffusive forces. Phase shifted AC signal is applied to the alternating electrodes for achieving the mixing of two different colloidal suspensions. The results indicate that the electric field and DEP forces are maximum at the edges of the electrodes and become minimum elsewhere. As compared to curved edges, straight edges of electrodes have lower electric field and DEP forces. The results also indicate that DEP force decays exponentially along the height of the channel. The effect of DEP forces on the concentration profile is studied. It is observed that, the concentration of colloidal particles at the electrodes edges is very less compared to elsewhere. Mixing of two colloidal suspensions due to diffusion is observed at the interface of the two suspensions. The improvement in mixing after applying the repulsive DEP forces on the colloidal suspension is observed. Most of the mixing takes place across the slant edges of the triangular electrodes. The effect of electrode pairs and the mixing length on degree of mixing efficiency are also observed.

Non-Spheric Colloidal Suspensions in Three-Dimensional Space

1997 ◽  
Vol 08 (04) ◽  
pp. 985-997 ◽  
Author(s):  
Dewei Qi
Keyword(s):  
Reynolds Number ◽  
Dimensional Space ◽  
Low Reynolds Number ◽  
Paper Industry ◽  
Three Dimensional ◽  
Colloidal Suspensions ◽  
Solid Particles ◽  
Spherical Particles ◽  
Dynamic Simulations ◽  
Low Reynolds

The translation and rotation of non-spherical particles, such as ellipsoidal, cylindric or disk-like pigment particles, in a Couette flow system similar to a blade coating system in the paper industry6 have been successfully simulated by using the lattice-Boltzmann method combined with Newtonian dynamic simulations. Hydrodynamic forces and torques are obtained by the use of boundary conditions which match the moving surface of solid particles. Then Euler equations have been integrated to include three-dimensional rotations of the suspensions by using four quaternion parameters as generalized coordinates. The three-dimensional rotations have been clearly observed. Consequently, the motion of the particles suspended in fluids of both low-Reynolds-number and finite-Reynolds-number, up to several hundreds, has been studied. It appears that the 3D translation and rotation of the non-spherical particles are more clearly observed in a high-Reynolds-number fluid than in a low-Reynolds-number fluid.

A Comparative Study of Optimisation Methods for Aerodynamic Design of Turbomachinery Blades

2000 ◽  
Author(s):  
Shahrokh Shahpar
Keyword(s):  
Stokes Equations ◽  
Guide Vane ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Analysis Tool ◽  
Geometrical Constraints ◽  
Gradient Based ◽  
Turbomachinery Blades ◽  
Optimisation Methods ◽  
Nozzle Guide

A new approach to three-dimensional design of turbomachinery blades is presented. A number of heuristic and gradient based optimisers are used in conjunction with a linear sensitivity analysis tool, FAITH, to re-design a turbine nozzle guide vane. A novel linear approach is used to eliminate the large computational costs usually associated with function evaluations which are essentially solutions to the Navier-Stokes equations. Results are compared with those obtained previously from the inverse design mode of FAITH. With the present approach, it is shown that nonlinear complicated cost functions can be reduced significantly and aerodynamic and geometrical constraints can be handled easily and efficiently.

Numerical Modeling of Fragmentation Characteristics of Explosive Fragmentation Munitions

2002 ◽  
Author(s):  
Vladimir M. Gold
Keyword(s):  
High Speed ◽  
Average Length ◽  
Three Dimensional ◽  
Fragmentation Model ◽  
Computational Technique ◽  
Entire Body ◽  
Detonation Products ◽  
Explosive Fragmentation ◽  
Break Up ◽  
The Moment

Numerical simulations of explosive fragmentation munitions presented in this work integrate three-dimensional axisymmetric hydrocode analyses with analytical fragmentation modeling. The developed analytical fragmentation model is based on the Mott’s theory of break-up of cylindrical “ring-bombs” (Mott, 1947), in which the average length of fragments is a function of the radius and velocity of the ring at the moment of break-up, and the mechanical properties of the metal. The fundamental assumption of the model is that the fragmentation occurs instantly throughout the entire body of the shell. Adopting Mott’s critical fracture strain concept (Mott, 1947), the moment of the shell break-up is identified in terms of the high explosive detonation products volume expansions, V/V0. The assumed fragmentation time determined from the high-speed photographic data of Pearson (1990) had been approximately three volume expansions, the fragmentation being defined as the instant at which the detonation products first appear as they emanate from the fractures in the shell. The newly developed computational technique is applied to both the natural and preformed explosive fragmentation munitions problems. Considering relative simplicity of the model, the accuracy of the prediction of fragment spray experimental data is rather remarkable.

Simulation of Gas – Non-Newtonian Liquid Flow in a Rectangular Bubble Column by Considering Bubbles Interactions

2012 ◽  
Author(s):  
Erfan Niazi ◽  
Mehrzad Shams ◽  
Arash Elahi ◽  
Goodarz Ahmadi
Keyword(s):  
Liquid Flow ◽  
Bubble Column ◽  
Three Dimensional ◽  
Methyl Cellulose ◽  
Newtonian Liquid ◽  
Bubble Coalescence ◽  
Break Up ◽  
Bubble Rising ◽  
Momentum Coupling ◽  
Fluid Rheology

In this article a CFD model of a three-dimensional Eulerian-Lagrangian is developed for a gas - non-Newtonian liquid flow in a rectangular column. The model resolves the time-dependent, three-dimensional motion of gas bubbles in a liquid to simulate the trajectory of bubbles. Our model incorporates drag, gravity, buoyancy, lift, pressure gradient and virtual mass forces acting on a bubble rising in a liquid, and accounts for two-way momentum coupling between the phases. Population balance equation is solved to model bubble coalescence and break up. In bubble coalescence, Prince and Blanch model is used which can consider the effect of fluid rheology. Luo and Svendosen model was selected for bubble break up. The standard k-e turbulence model is selected for calculating turbulent flow properties. Power-law non-Newtonian liquid is selected for analysis of effect of different solutions of carboxy methyl cellulose in water. The effect of changing fluid to non-Newtonian is discussed in terms of velocity profile and gas hold up.

scholarly journals THE PROTON-DEUTERON BREAK-UP PROCESS IN A THREE-DIMENSIONAL APPROACH

2003 ◽  
Vol 18 (02n06) ◽  
pp. 452-455 ◽  
Author(s):  
IMAM FACHRUDDIN ◽  
CHARLOTTE ELSTER ◽  
WALTER GLÖCKLE
Keyword(s):  
Partial Wave ◽  
Cross Section ◽  
Three Dimensional ◽  
Relativistic Effects ◽  
Peak Height ◽  
Partial Wave Decomposition ◽  
Leading Term ◽  
Break Up ◽  
The Cross ◽  
Wave Decomposition

The pd break-up amplitude in the Faddeev scheme is calculated by employing a three-dimensional method without partial wave decomposition (PWD). In the first step and in view of higher energies only the leading term is evaluated and this for the process d(p,n)pp. A comparison with the results based on PWD reveals discrepancies in the cross section around 200 MeV. This indicates the onset of a limitation of the partial wave scheme. Also around 200 MeV relativistic effects are clearly visible and the use of relativistic kinematics shifts the cross section peak to where the experimental peak is located. The theoretical peak height, however, is wrong and calls first of all for the inclusion of rescattering terms, which are shown to be important in a nonrelativistic full Faddeev calculation in PWD.

scholarly journals Distinctive diffusive properties of swimming planktonic copepods in different environmental conditions

2018 ◽  
Author(s):  
Raffaele Pastore ◽  
Marco Uttieri ◽  
Giuseppe Bianco ◽  
Maurizio Ribera d’Alcalá ◽  
Maria Grazia Mazzocchi
Keyword(s):  
Three Dimensional ◽  
Mean Square Displacement ◽  
Vertical Direction ◽  
Colloidal Suspensions ◽  
Individual Variability ◽  
Dynamic Correlation ◽  
Single Organism ◽  
Wide Range ◽  
Planktonic Copepods ◽  
Simple Average

AbstractSuspensions of small planktonic copepods represent a special category in the realm of active matter, as their size falls within the range of colloids, while their motion is so complex that it cannot be rationalized according to basic self-propelled particle models. Indeed, the wide range of individual variability and swimming patterns resemble the behaviour of much larger animals. By analysing hundreds of three dimensional trajectories of the planktonic copepod Clausocalanus furcatus we investigate the possibility of detecting how the motion of this species is affected by different external conditions, such as the presence of food and the effect of gravity. While this goal is hardly achievable by direct inspection of single organism trajectories, we show that this is possible by focussing on simple average metrics commonly used to characterize colloidal suspensions, such as the mean square displacement and the dynamic correlation functions. We find that the presence of food leads to the onset of a clear localization that separates a short-time ballistic from a long-time diffusive regime. Such a benchmark reflects the tendency of C. furcatus to remain temporally feeding in a limited space and disappears when food is absent. Localization is clearly evident in the horizontal plane, but is negligible in the vertical direction, due to the effect of gravity. Our results suggest that simple average descriptors may provide concise and useful information on the swimming properties of planktonic copepods, even though single organism behaviours are strongly heterogeneous.

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