scholarly journals Encapsulation of Droplets Using Cusp Formation behind a Drop Rising in a Non-Newtonian Fluid

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 54 ◽  
Author(s):  
Raphaël Poryles ◽  
Roberto Zenit
Keyword(s):  
Critical Velocity ◽  
Newtonian Fluid ◽  
Formation Process ◽  
Critical Size ◽  
Long Tail ◽  
Capillary Effects ◽  
Velocity Discontinuity ◽  
Two Fluids ◽  
Viscous Solution ◽  
Surrounding Liquid

The rising of a Newtonian oil drop in a non-Newtonian viscous solution is studied experimentally. In this case, the shape of the ascending drop is strongly affected by the viscoelastic and shear-thinning properties of the surrounding liquid. We found that the so-called velocity discontinuity phenomena is observed for drops larger than a certain critical size. Beyond the critical velocity, the formation of a long tail is observed, from which small droplets are continuously emitted. We determined that the fragmentation of the tail results mainly from the effect of capillary effects. We explore the idea of using this configuration as a new encapsulation technique, where the size and frequency of droplets are directly related to the volume of the main rising drop, for the particular pair of fluids used. These experimental results could lead to other investigations, which could help to predict the droplet formation process by tuning the two fluids’ properties, and adjusting only the volume of the main drop.

scholarly journals Encapsulation of Droplets Using Cusp Formation Behind a Drop Rising in a Non-Newtonian Fluid

2018 ◽  
Author(s):  
Raphael Poryles ◽  
Roberto Zenit
Keyword(s):  
Critical Velocity ◽  
Newtonian Fluid ◽  
Critical Size ◽  
Long Tail ◽  
Capillary Effects ◽  
Velocity Discontinuity ◽  
Viscous Solution ◽  
Cusp Formation ◽  
Surrounding Liquid

The rising of an oil drop in a non-Newtonian viscous solution is studied experimentally. In this case, the shape of the ascending drop is strongly affected by the non-Newtonian properties of the surrounding liquid. We found that the so-called velocity discontinuity phenomena is observed for drops larger than a certain critical size. Beyond the critical velocity, the formation of a long tail is observed, from which small droplets are continuously emitted. We determined that the fragmentation of the tail results mainly from the effect of capillary effects. We explore the idea of using this configuration as a new encapsulation technique, where the size and frequency of droplets can be well predicted.

Ligament Flows of Exit-Pinching During Drop-on-Demand Inkjetting of Alginate Solution

2016 ◽  
Author(s):  
Mengyun Zhang ◽  
Changxue Xu
Keyword(s):  
Inkjet Printing ◽  
Formation Process ◽  
Droplet Formation ◽  
Artificial Organs ◽  
Excitation Voltage ◽  
Capillary Effects ◽  
Alginate Solution ◽  
Nozzle Orifice ◽  
Organ Printing ◽  
Flow Directions

Organ printing is an emerging technology for fabricating artificial tissues and organs, which are constructed layer by layer by precisely placing tissue spheroids or filaments as building blocks. These fabricated artificial organs offers a great potential as alternatives to replace the damaged human organs, providing a promising solution to solve organ donor shortage problem. Inkjetting, one of the key technologies in organ printing, has been widely developed for organ printing because of its moderate fabrication cost, good process controllability and scale-up potentials. Droplet formation process as the first step towards inkjetting 3D cellular structures needs to be studied and controlled precisely. This paper focuses on the ligament flow of exit-pinching during droplet formation process of inkjet printing. The ligament flow directions during pinch-off process of inkjet printing of a sodium alginate solution with a concentration of 0.5% (w/v) have been studied. It is found that two different types of flow directions inside a single ligament during pinch-off process may occur. At an excitation voltage of 30 V, the ligament flow has two different directions at the locations near the nozzle orifice and the jet front head: the negative z direction at the location near the nozzle orifice due to the dominant capillary effect, and the positive z direction at the location near the jet front head due to both the fluid inertial and capillary effects. On the contrary, at an excitation voltage of 70 V, the ligament flow directions are the same at the locations near the nozzle orifice and the jet front head: the positive z direction at the location near the nozzle orifice due to the sufficiently large fluid inertial effect, and the same positive z direction at the location near the jet front head due to both the fluid inertial and capillary effects. Two flow directions inside a single ligament benefit single droplet formation without satellite droplets, but the droplet trajectory will be easily affected by the airflow in the laboratory due to the small droplet velocity as well as the droplet deposition accuracy. Single flow direction inside a single ligament usually results in a long ligament due to the large fluid inertia which eventually breaks into several undesirable satellite droplets. The resulting knowledge will be beneficial for better understanding of the ligament pinch-off during droplet formation process of inkjet printing biological viscoelastic alginate bioink for 3D cellular structure fabrication as well as precise droplet controllability for good quality of fabricated 3D structures.

A Theory of Hydrodynamic Lubrication Involving the Mixture of Two Fluids

1994 ◽  
Vol 61 (3) ◽  
pp. 634-641 ◽  
Author(s):  
F. Dai ◽  
M. M. Khonsari
Keyword(s):  
Continuum Mechanics ◽  
Newtonian Fluid ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Incompressible Fluids ◽  
Theoretical Development ◽  
Governing Equations ◽  
Power Law Fluid ◽  
Two Fluids ◽  
Special Cases

Based on the principles of continuum mechanics, we drive the governing equations for the hydrodynamic lubrication involving the mixture of two incompressible fluids. The governing equations are general in the sense that they can be applied to the mixture of any simple non-Newtonian fluid with a Newtonian fluid. A mixture thus formed is considered to be nonhomogeneous and non-Newtonian. In the theoretical development, the interaction between the constituents is taken into consideration. It is shown that a number of currently available models are special cases of the theory presented in this paper. As an example, results are presented for journal bearing performance lubricated with a mixture of a power-law fluid mixed with Newtonian oil.

Fingering instabilities in vertical miscible displacement flows in porous media

1995 ◽  
Vol 288 ◽  
pp. 75-102 ◽  
Author(s):  
O. Manickam ◽  
G. M. Homsy
Keyword(s):  
Porous Media ◽  
Stability Analysis ◽  
Linear Stability ◽  
Critical Velocity ◽  
Linear Stability Analysis ◽  
Miscible Displacement ◽  
Stable Region ◽  
Miscible Displacements ◽  
Flows In Porous Media ◽  
Two Fluids

The fingering instabilities in vertical miscible displacement flows in porous media driven by both viscosity and density contrasts are studied using linear stability analysis and direct numerical simulations. The conditions under which vertical flows are different from horizontal flows are derived. A linear stability analysis of a sharp interface gives an expression for the critical velocity that determines the stability of the flow. It is shown that the critical velocity does not remain constant but changes as the two fluids disperse into each other. In a diffused profile, the flow can develop a potentially stable region followed downstream by a potentially unstable region or vice versa depending on the flow velocity, viscosity and density profiles, leading to the potential for ‘reverse’ fingering. As the flow evolves into the nonlinear regime, the strength and location of the stable region changes, which adds to the complexity and richness of finger propagation. The flow is numerically simulated using a Hartley-transform-based spectral method to study the nonlinear evolution of the instabilities. The simulations are validated by comparing to experiments. Miscible displacements with linear density and exponential viscosity dependencies on concentration are simulated to study the effects of stable zones on finger propagation. The growth rates of the mixing zone are parametrically obtained for various injection velocities and viscosity ratios.

scholarly journals Breaking up of a drop of viscous liquid immersed in another viscous fluid which is extending at a uniform rate

1936 ◽  
Vol 153 (879) ◽  
pp. 302-318 ◽  
Keyword(s):  
Viscous Fluid ◽  
Viscous Liquid ◽  
Experimental Studies ◽  
Lubricating Oil ◽  
Disruptive Effect ◽  
Viscous Forces ◽  
Two Fluids ◽  
Initial Drop ◽  
Break Up ◽  
Surrounding Liquid

1—In a previous papers the present writer has discussed the instability of a long cylindrical column of an incompressible viscous liquid surrounded by another viscous fluid under the action of both surface tension and viscous forces. In this work the fluids were at rest except for the small disturbances which were assumed to develop slowly. It was shown that if the ratio of viscosities of the two fluids is neither zero nor infinity the maximum instability always occurs at a certain definite value of the wavelength of the assumed initial varicosity so that the formation of drops of definite size would be expected. A comparison of the theory with observation has also been made and satisfactorily good agreement between them was found. Now, in his experimental studies on the mode of formation of a cylindrical thread from a drop of a viscous liquid by the disruptive effect of the viscous drags of a surrounding liquid, professor G. I. Taylor observed that when a drop of black lubricating oil was surrounded by syrup, the thread formed by pulling out the drop did not at once break up into small drops but remained cylindrical for some time and finally broke up into small drops, the diameters of which were about 1/10th of the diameter of the original drop. On the other band, if as soon as the cylindrical thread was formed the apparatus was stopped the thread immediately began to break up in the manner described above. Thus, if the apparatus were kept going very much smaller drops were formed than if it were stopped as soon as the initial drop bad been pulled out into a cylindrical thread.

scholarly journals HYPERBOLIC DESCRIPTION OF CONTAMINATED FLOW THROUGH AN UNSATURATED WELLBORE

2007 ◽  
Vol 6 (1) ◽  
pp. 11
Author(s):  
M. L. Martins-Costa ◽  
R. M. Saldanha da Gama ◽  
J. H. Carneiro de Araujo
Keyword(s):  
Newtonian Fluid ◽  
Nonlinear Partial Differential Equations ◽  
Operator Splitting ◽  
Mixture Theory ◽  
Porous Matrix ◽  
Theory Approach ◽  
Splitting Technique ◽  
Two Fluids ◽  
Nonlinear Hyperbolic System ◽  
Solid Liquid

This work studies the flow of a mixture of two fluids – a Newtonian fluid and a pollutant – through a rigid cylindrical shell porous matrix. Aiming to build a preliminary local model for the flow of a Newtonian fluid containing a pollutant through a wellbore, a mixture theory approach is employed. The mixture consists of four overlapping continuous constituents: one solid (porous medium), one liquid (Newtonian fluid), the pollutant (solid, liquid or gas) and an inert gas included to account for the compressibility of the mixture as a whole. Assuming the flow on radial direction only, a set of three nonlinear partial differential equations describes the problem. Combining Glimm’s scheme with an operator splitting technique to account for the non-homogeneous part of the hyperbolic operator, the resulting nonlinear hyperbolic system is numerically approximated. Representative results illustrating the numerical methodology are presented.

scholarly journals Multifluid squirt flow and hysteresis effects on the bulk modulus–water saturation relationship

2015 ◽  
Vol 203 (2) ◽  
pp. 814-817 ◽  
Author(s):  
G. Papageorgiou ◽  
M. Chapman
Keyword(s):  
Bulk Modulus ◽  
Elastic Properties ◽  
Wave Speed ◽  
Water Saturation ◽  
Spatial Distributions ◽  
Capillary Effects ◽  
Volume Fractions ◽  
Two Fluids ◽  
Fluid Properties

Abstract Many applications of seismology require the calculation of wave speed and attenuation in rocks saturated with multiple fluids. Squirt flow is known to be an important effect in fully saturated rocks but the extension to the multifluid case is unclear. Neglecting capillary effects, we generalize previous work on squirt flow to the case where two fluids are present. We derive expressions for the effective fluid properties, but the results depend on the spatial distributions, and not only volume fractions, of the two fluids. Our results demonstrate that such multifluid squirt flow may be responsible for hysteresis effects in elastic properties during imbibition and drainage.

A linear model of a finite amplitude Helmholtz instability

1974 ◽  
Vol 338 (1612) ◽  
pp. 17-41 ◽  
Keyword(s):  
Linear Model ◽  
Critical Size ◽  
Harmonic Wave ◽  
Vortex Sheet ◽  
Finite Amplitude ◽  
Helmholtz Instability ◽  
Central Importance ◽  
Two Fluids ◽  
Onset Of Turbulence ◽  
Definition Of

The Helmholtz instability of a vortex sheet separating two fluids in relative motion is un­bounded in a simple linear model of the interaction of sound with the sheet. This paper presents a model which limits the amplitude of a harmonic wave in a physically realistic way but remains mathematically tractable. It is based on the idea that growth is limited by the onset of turbulence between the fluids when the Helmholtz wave reaches a critical size. An important consequence of the theory is a strong enhancement of the sound scattered up­stream, which is significant both in the context of forward noise produced by a jet and possibly also of jet screech. The requirement of causality is of central importance in determining the correct solution, and detailed general results on the theory of zero ultradistribu­tions are presented to establish an analytic definition of causality for the class of solutions encountered.

A note on the damping and oscillations of a fluid drop moving in another fluid

1969 ◽  
Vol 37 (4) ◽  
pp. 715-725 ◽  
Author(s):  
S. V. Subramanyam
Keyword(s):  
Weber Number ◽  
Critical Size ◽  
Correction Term ◽  
Frequency Mode ◽  
Viscous Effects ◽  
Fluid Medium ◽  
Two Fluids ◽  
Fluid Drop ◽  
Two Phases ◽  
Lower Frequency Mode

The oscillations of a drop moving in another fluid medium have been studied at low values of Reynolds number and Weber number by taking into consideration the shape of the drop and the viscosities of the two phases in addition to the interfacial tension. The deformation of the drop modifies the Lamb's expression for frequency by including a correction term while the viscous effects split the frequency into a pair of frequencies—one lower and the other higher than Lamb's. The lower frequency mode has ample experimental support while the higher frequency mode has also been observed. The two modes almost merge with Lamb's frequency for the asymptotic cases of a drop in free space or a bubble in a dense viscous fluid but the splitting becomes large when the two fluids have similar properties. Instead of oscillations, aperiodic damping modes are found to occur in drops with sizes smaller than a critical size ($\sim\hat{\rho}\hat{\nu}^2/T $). With the help of these calculations, many of the available experimental results are analyzed and discussed.

Voids in Quenched Nickel

1968 ◽  
Vol 26 ◽  
pp. 266-267
Author(s):  
J. J. Laidler
Keyword(s):  
Electron Beam ◽  
Ambient Temperature ◽  
Cooling Rate ◽  
Three Dimensional ◽  
Cooling Curve ◽  
Polycrystalline Nickel ◽  
Quenching Temperature ◽  
Long Tail ◽  
Diffusion Pump

The presence of three-dimensional voids in quenched metals has long been suspected, and voids have indeed been observed directly in a number of metals. These include aluminum, platinum, and copper, silver and gold. Attempts at the production of observable quenched-in defects in nickel have been generally unsuccessful, so the present work was initiated in order to establish the conditions under which such defects may be formed.Electron beam zone-melted polycrystalline nickel foils, 99.997% pure, were quenched from 1420°C in an evacuated chamber into a bath containing a silicone diffusion pump fluid . The pressure in the chamber at the quenching temperature was less than 10-5 Torr . With an oil quench such as this, the cooling rate is approximately 5,000°C/second above 400°C; below 400°C, the cooling curve has a long tail. Therefore, the quenched specimens are aged in place for several seconds at a temperature which continuously approaches the ambient temperature of the system.

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