Increase In Phase Velocity Research Articles

Impurities removal from acidic solution of nickel cobalt complex hydroxide using pulsed disc and doughnut column

In this work, a 30 mm diameter pulsed disc and doughnut solvent extraction column was used for impurities removal from nickel cobalt complex hydroxide acid solution by solvent extraction. The effects of dispersed phase velocity, continuous phase velocity and pulse intensity on drop diameter, dispersed phase holdup and mass transfer were investigated. The results show that the drop size decreases gradually, and the dispersed phase holdup decreased initially and then increased with the increase of pulse intensity. The dispersed phase holdup increases with the increase of dispersed phase velocity but is independent of the continuous phase velocity. The experimental data of this study are predicted by correlations with regressed parameters. The average absolute relative error of drop size and dispersed phase holdup were 10.07 % and 18.28 %. With the increase of pulse intensity, the extraction efficiency of impurities decreased firstly and then increased. The number of mass transfer units and the height of mass transfer unit were calculated. The trend of number of mass transfer units of impurities are similar to extraction efficiency. Mass transfer results indicate that pulsed disc and doughnut column can be applied to the nickel cobalt complex hydroxide acid solution-P204/kerosene system.

Mathematical Analysis on Dispersion Relation of Rayleigh Wave for an Initially Stressed Magneto-Poroelastic Material with Corrugated and Impedance Boundary

This study showcases the Mathematical modelling of elastic surface waves and the analysis of dispersion relations of Rayleigh-type of wave in an initially stressed homogeneous porous magneto-elastic material having corrugated and impedance boundary exhibitions. Adoption of the classical harmonic method of wave analysis, non-dimensionalization of the resulting equations of motion, and corrugated-impedance boundary conditions produced by the modeled problem are also captured. The dispersion equation was analytically and graphically presented. Effects of the contributing physical quantities, such as impedance and corrugated boundary parameters, on Rayleigh waves for the chosen material are analyzed. The magnetic field’s influences and the wavenumber associated with the corrugated boundary surfaces on the material increase the dispersion relations of the Rayleigh wave profile on the material. In addition, we noted that the dispersion relations of the wave increases for increasing phase velocity and some parameters of voids. Also, a void parameter triggered a decrease on the dispersion profile of the Rayleigh wave when increased while noting some uniform exhibitions from other voids coefficients. This work holds the potential to provide more insights into studies involving displacement distributions in earthquake sciences, stress-strain analysis in Structural Engineering materials, among others.

Hydrodynamic characteristics of core/shell microdroplets formation: Map of the flow patterns in double-T microchannel

Liquid-liquid–liquid (L/L/L) flows in microchannels involving three-phase interactions are important in various chemical applications that entail liquid–liquid–liquid reactions. This work comprehensively investigates core (silicone oil)/shell (Polycaprolactone) microdroplet formation using a continuous third phase (distilled water) in a double T-junction microchannel with a diameter of 600 µm, employing Volume-of-Fluid (VOF) simulations and high-speed imaging experimental observation. Due to the satisfactory agreement between computational and experimental techniques, the theoretical flow patterns were identified and categorized into three distinct categories at various flow rates of three phases: core/shell dripping, core/shell slug, and core/shell jetting. The shell thickness increases as the ratio of shell to core phase velocity (ushell:ucore) increases. Based on the continuous phase Capillary number (Cac) and core and shell phases Weber number (Wecore,shell), a flow pattern map was generated that segregates the distinct flow patterns into different regions. When the flow of the core and shell phases fails to form a droplet due to the inertia of the continuous phase, a core/shell dripping/slug pattern is observed. The channel walls encompass the droplets that form in the slug pattern (2×10-5≤Cac≤5×10-4, 0<Weshell≤1.5×10-3, and 0<Wecore≤5×10-5) because the continuous phase has less inertia, whereas, in the dripping pattern (5.5×10-5≤Cac≤9×10-4, 7×10-5≤Weshell≤2.5×10-4, and 1×10-5≤Wecore≤7×10-5), the shell phase fluid is enclosed by the continuous phase. The transition from dripping to jetting (Cac≥0.5, 0<Weshell≤0.15, and 1×10-2≤Wecore≤8×10-2) occurs as the flow rate of a continuous fluid or shell fluid increases. A dimensionless correlation for shell thickness estimation with a 12 % tolerance was proposed with a core/shell/continuous phase's physical properties, surface tensions, and microdroplet size, using Buckingham's theory based on 200 CFD simulations. Additionally, the flow rate and viscosity substantially impact the internal fluid velocity and vorticity of core/shell microdroplets, whereas the influence of interfacial tension can be disregarded. This research lays the groundwork for future studies on mass transfer and reaction behaviors in liquid–liquid–liquid three-phase flow in double T-junction microchannels by exploring various hydrodynamic characteristics under different operating conditions for core/shell microdroplet formation.

Wave propagation analysis in pre-stressed incompressible hyperelastic multi-layered plates using a plate theory

Wave propagation analysis of pre-stressed incompressible hyperelastic thin multi-layered plates is developed based on the first-order shear deformation plate theory (FSDT) with second order thickness extensibility. Variables describing the thickness-direction deformation are obtained from the incompressibility condition. The incremental theory of nonlinear elasticity is employed in conjunction with a plate theory. The multi-layered plate is assumed to be symmetric in the thickness direction. Since the plate theory has not been used for the wave propagation analysis of hyperelastic plates, the results of flexural wave modes are compared with results of the straight-crested flexural waves based on the three-dimensional (3D) elasticity theory available in the literature and the results for in-plane wave modes are compared with those developed in this study using the plane-stress elasticity theory. The dispersion curves of both extensional and flexural waves for single-layer and three-layer plates are presented and the effects of different parameters including the homogenous pre-stretch, the wave propagation direction and the plate initial thickness on the dispersion curves are discussed in detail. The results indicate that the phase speed of the extensional waves depends on the wave propagation angle due to the induced anisotropy. As the overall shear modulus of the three-layer plate increases, the phase velocity increases. Also, the effect of pre-stretch and thickness on phase speed of flexural waves is not pronounced for high frequencies.

Transition from bubbling to jetting in submerged gas-liquid jets through a minichannel

This paper provides a first insight into the transition from bubbling to jetting of submerged jets generated by the ejection of gas-liquid mixing flows through a minichannel into water. The ejections of rivulet, annular, churn, and Taylor-annular flows are found to generate jet behaviors of aperiodic bubbling, impact bubbling, chaotic bubbling, jetting-like jets, unstable jetting, and stable jetting. The correspondence relationship between the in-channel flows and submerged jets is revealed by establishing their flow regime maps, as well as the prediction models of transition boundaries. Compared to single-phase gas jets, the participation of liquid phase in mixing flows significantly promotes the transition from bubbling to jetting. Specifically, the increase of liquid phase velocity decreases the critical gas phase velocity for the transition from bubbling to jetting-like jets, as well as the transition from unstable jetting to stable jetting, characterized by the increase of liquid slug frequency and jet penetration length, as well as the decrease of liquid slug length, jet pitch-off frequency, and jet cone angles. As a result, via the in-channel mixing with a liquid phase of a Weber number of 110 prior to orifice ejection, the critical Mach number for the onset of stable jetting is significantly reduced from 3.76 to 1.25.

Small amplitude dust acoustic solitary waves in a magnetized dusty plasma with nonthermal distribution for both electrons and ions

The propagation of dust acoustic solitary waves (DASWs) has been investigated in a magnetized dusty plasma consisting of negatively charged dust particles, nonthermal ions and nonthermal electrons. Using reductive perturbation method, the Korteweg-de-Vries (K-dV) equation is derived. It is found that the basic structures (such as polarity, amplitude, width) of DASWs are influenced by nonthermal ions and nonthermal electrons. The results show that both compressive and rarefactive DASWs exist in such dusty plasma. It is observed that by increasing the nonthermality parameter of ions and electrons, the nonlinear wave phase velocity increases. Furthermore, nonthermal distributed ions have more effect on the nonlinear wave phase velocity of the DASWs than nonthermal distributed electrons. The dependence of the angle that the external magnetic field makes with the propagation direction of wave on the amplitude and width of DASWs has been also investigated. It was concluded that this angle strongly affects the DASWs. Finally, the effect of the magnetic field appears only in the width and not in the amplitude of the DASWs. The findings of this study can be helpful in understanding the structures of DASWs in the dusty plasma in which both nonthermal ions and nonthermal electrons exist. Such structures can be found in different regions of space and astrophysics mediums such as the upper ionosphere and Saturn’s E-ring.

Numerical Analysis of Linear Traveling Wave in Rotating Rayleigh–Bénard Convection with an Adiabatic Sidewall

In rotating Rayleigh–Bénard problems, convection with traveling waves may occur near the sidewalls. The Rayleigh number, Taylor number and Prandtl number are involved in this phenomenon, and the convection mode is determined depending on their values. We focused on the onset of this convection with traveling waves under the assumption that centrifugal force is neglected. By conducting two-dimensional linear stability analyses assuming periodicity of the flow and temperature fields along the sidewall direction, we investigated the effect of the Taylor number and the Prandtl number on the critical Rayleigh number and also attempted to understand the phenomenon qualitatively through three-dimensional visualizations. It was exhibited that as the Taylor number increases, the wave number, the Rayleigh number and the phase speed are found to increase. On the other hand, as the Prandtl number decreases, the wavenumber and the Rayleigh number decrease, but the phase velocity increases. The present analyses suggest that convection modes localized near the sidewalls are unlikely to emerge for low Prandtl number cases, which are comparable to those of liquid metals.

Rayleigh waves in nonpolar Al0.7Sc0.3N(112¯0) films with enhanced electromechanical coupling and quality factor

This work reports on the growth of 1 µm nonpolar a-plane Al0.7Sc0.3N(112¯0) thin films on an r-plane sapphire Al2O3(11¯02) via magnetron sputter epitaxy. The electro-acoustic properties of the film structures were characterized using surface acoustic wave (SAW) resonators. Measured electrical responses were found to be strongly anisotropic in terms of the wave propagation direction. We identified a sagittal polarized Rayleigh wave mode with large coupling (keff2= 3.7%), increased phase velocity (v= 4825 m/s), as well as high quality factor (Q &amp;gt; 1000) for SAW propagation along the c-axis [0001] and normalized thicknesses h/λ=0.2. Finite element method simulations using electro-acoustic properties of Al0.7Sc0.3N obtained from the density functional theory reproduce our experimental results.

Investigation of the extraction of natural alkaloids in Karr reciprocating plate columns: Fluid dynamic study

Previous work found that 0.2 M Cyanex® 923 in xylene has potential to extract natural alkaloids such as morphine. In this work, pilot scale fluid dynamic tests using 0.2 M Cyanex® 923 in xylene as a dispersed phase and water as a continuous phase in a reciprocating plate Karr column were conducted at different flowrates of both phases and reciprocating frequencies. The results show that the dispersed phase liquid holdup increases with the increase of dispersed phase velocity and reciprocating frequency, and the Sauter-mean drop diameter is independent of the velocity of both phases, and it slightly reduces with increasing reciprocating frequency. The results were used to regress an empirical model. In addition, morphine extraction using the same solvents were also studied in two different Karr columns. The results were consistent with those of fluid dynamic tests, and further used to investigate the regressed model within 30 % deviation.

Wave propagation and vibration analysis of sandwich structure with a bio-based flexible core and composite face sheets subjected to visco-Pasternak foundation and magnetic field

In this study, the wave propagation and vibration analysis of sandwich structure with a bio-based flexible core and composite face sheets subjected to magnetic field are studied. In the present analysis, the material properties of composite face sheets are assumed viscoelastic based on Kelvin -Voigt model, and high-order sandwich panels theory is used for core modeling. The analysis of wave propagation and vibration of the sandwich structure is performed assuming complete adhesion between core and face sheets, and the governing equations of motion are derived by Hamilton's principle. Finally, the semi-analytical solution is applied to obtain the effects of the structural and foundation damping coefficients, different angles of the layers, the ratio of width to thickness, the ratio of the thickness of the core to the procedures, temperature variations, wave number, aspect ratios, elastic properties and number of layers on the wave propagation behavior of the sandwich plate for complete adhesion between layers. The results show that by increasing the ratio of the thickness of the core to the layers, the velocity of the wave propagation initially increases, and then decreases. Also, the application of the magnetic field has an increasing effect on the sandwich plate frequency. Finally, with the increase in the number of layers and the number of waves, the phase velocity increases, while the hardness of the system decreases when the temperature and damping coefficient rises.

Computational analysis on unsteady hydromagnetic Couette flow of fluid—Particle suspension in an accelerated porous channel

In this analysis, Semi-analytical solution representing the time dependent Couette flow of conducting fluid–particle suspension in a permeable channel is offered in the existence of a magnetic field. The magnetic field is anticipated to be positioned either with the conducting suspension or the velocity of the magnetic field is same with the moving wall. Solution to the dimensionless coupled equations are provided by adopting the well known Laplace transform technique and D’Alermbert Method for both flow cases. The obtained solutions are later inverted to the time domain with the help of the Riemann sum approximation. Numerical values for fluid–particle suspension was validated with existing benchmark. Expressions for fluid–particle velocity and their corresponding skin fiction are also found in both cases. Influence of a number of flow parameters on flow formation are demonstrated via graphs. Results indicate that, irrespective of the magnetic field positioned either with the conducting suspension or with the moving wall, injection velocity strengthens the momentum boundary layer yielding an increase in fluid phase velocity and particle phase velocity, whereas the contrast is true with suction.

Coupling and Instability of Electrostatic Waves in Spin Magnetized Degenerate Plasmas

In this article, we study the coupling of low-frequency electrostatic waves in the electron-ion and the electron-ion-beam-spin quantum plasmas. The quantum effect of electrons are introduced via separate spin evolution-quantum hydrodynamic (SSE-QHD) model while the ion dynamics is governed by classical fluid equations. In the case of electron-ion plasma, it is found that the quantum effects shift both the coupling domain and the phase velocities of coupled waves. Furthermore, the coupling is observed to be strong at small propagation angles. In the beam interacting system, two coupling domains occur corresponding to small and large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -values. In the first domain beam mode excites the ion cyclotron (IC) wave and moves with constant phase velocity while in the second domain it gains energy from the ion acoustic (IA) mode and travels with increasing phase velocity. In addition, the beam parameters affect both the coupling domain and the phase velocity. The presence of beam in electron-ion plasma drives the IC mode unstable. The beam parameters, the spin, and the obliqueness affect the instability. Our findings may be helpful in understanding the energy exchange of plasma waves via coupling phenomenon in degenerate plasma systems.

Laboratory Measurements of the Impact of Fracture and Fluid Properties on the Propagation of Krauklis Waves

AbstractThe Krauklis wave is a slow dispersive wave, generated in fluid‐filled fractures. By analyzing the resonant frequency and quality factor of the Krauklis wave, the fracture dimension and fluid properties can be estimated. However, the accuracy of the estimation of fracture dimension and fluid properties depends on deciphering factors affecting the Krauklis wave such as fluid viscosity, fracture geometry, fracture compliance, and stiffness ratio, some of which have not been experimentally studied yet. We have developed an experimental apparatus to study the Krauklis wave within a trilayer model consisting of a pair of aluminum plates and a mediating viscous fluid layer. We utilize a piezoelectric source and miniature pressure transducers in our measurements. To evaluating the effects of the fracture aperture and fluid viscosity, we examine the impact of complex and realistic fracture geometry by introducing spatially varying aperture, surface roughness, and compliant partial surface contact provided by springs. The phase velocity, resonant frequencies, and quality factors (a) increase with the expansion of fracture aperture and (b) decrease with the increase of the fluid viscosity. Additionally, (c) phase velocity, resonant frequencies, and attenuation decrease with the increase of mechanical compliance. Furthermore, rough and wedge‐shaped fracture surfaces tend to slow down the Krauklis wave. Since the Krauklis wave is used by different disciplines such as volcanology, glaciology, and the petroleum industry to characterize fracture dimensions and properties of the fluids involved, our experimental findings can be used as a benchmark to develop comprehensive theoretical models to better interpret the Krauklis waves.

Comparison of Static Thermal Gradient to Isothermal Conditions in Gas Chromatography Using a Stochastic Transport Model.

This paper compares static (i.e., temporally unchanging) thermal gradient gas chromatography (GC) to isothermal GC using a stochastic transport model to simulate peak characteristics for the separation of C12-C14 hydrocarbons resulting from variations in injection bandwidth. All comparisons are made using chromatographic conditions that give approximately equal analyte retention times so that the resolution and number of theoretical plates can be clearly compared between simulations. Simulations show that resolution can be significantly improved using a linear thermal gradient along the entire column length. This is mainly achieved by partially compensating for loss in resolution from the increase in mobile phase velocity, which approximates an ideal, basic separation. The slope of the linear thermal gradient required to maximize resolution is a function of the retention parameters, which are specific to each analyte pair; a single static, thermal gradient will not affect all analytes equally. A static, non-linear thermal gradient that creates constant analyte velocities at all column locations provides the largest observed gains in resolution. From the simulations performed in this study, optimized linear thermal gradient conditions are shown to improve the resolution by as much as 8.8% over comparative isothermal conditions, even with a perfect injection (i.e., zero initial bandwidth).

Holdup and regime transition in reciprocating and rotating sieve plate column (RRSPC) for C6(mim)PF6 ionic liquid –water system

ABSTRACT In the present study, Reciprocating and Rotating Sieve Plate Column (RRSPC) was used with C6(mim)PF6; ionic liquid as dispersed phase and water as continuous phase to study hydrodynamics, which has not been studied till date. Experiments were conducted at different RPM, reciprocating pulsating frequency (RPF), dispersed phase velocity and total throughput, at different O/A ratios. It was found that disperse phase holdup increases with increase in dispersed phase velocity, total throughput (at different O/A ratios) and with increase in RPM/RPF. Simultaneous reciprocating pulsation and rotation produce good quality of dispersion of ionic liquid in range of 50 to 65 RPM/RPF. Phase inversion of dispersed phase to continuous phase takes place at 70 RPM/RPF when dispersed phase velocity () exceeds 4.2 mm/s. Higher holdup was observed at lower RPM/RPF in RRSPC as compared to other type of column reported in literature. The optimum operating condition for RRSPC was found to be, 60–65 RPM/RPF to achieve better holdup and uniform quality of dispersion. It turned to emulsion phase above 70 RPM/RPF. Snapshots show flow visualization as well as dispersion quality. Regime maps of the system were presented to understand the mixing settler regime, dispersion and emulsion regime ranges.

Analysis of the Effect of Sio2 Film on the Characteristics of Rayleigh Wave in Zno/Sic Structure

The influence of SiO2 film on the phase velocity and the electromechanical coupling coefficient of ZnO/SiC structure was analyzed by finite element method. The results show that the middle SiO2 film layer reduces the phase velocity of Rayleigh wave and significantly increases the electromechanical coupling coefficient. When the top SiO2 film layer thickness is larger than the ZnO film thickness, the Rayleigh wave phase velocity increases. Otherwise, the Rayleigh wave phase velocity decreases. The electromechanical coupling coefficient increases first and then decreases. These conclusions can guide the development of surface acoustic wave devices with high phase velocity and high electromechanical coupling coefficient.

Drop sizes and its distribution in jet-driven liquid–liquid mixing column: substantial application for the liquid–liquid extraction process

The present work reports the study of drop size distribution, drop aspect ratio, and interfacial area in a liquid–liquid jet-driven mixing column. Four different liquids, i.e., kerosene, diesel, 1-decanol, and paraffin, are used as dispersed phases and water as the continuous phase. The effect of the jet velocity, the volume fraction of the dispersed phase, and the physical properties of a liquid mixture such as density, viscosity, and surface tension are studied on the drop size distribution and drop aspect ratio. The column diameter of 0.37 m and nozzle diameter of 0.005 m were used. The velocity of the jet is varied between 0.68 m/s–1.71 m/s. It is observed that the drop size decreases as the volume fraction of the dispersed phase and jet velocity increases. Drop size distribution is found to follow the Log-logistic drop size distribution function. The aspect ratio is close to unity for a small drop, and it decreases as the drop size increases. The increase in the Eötvös number leads to a decrease in the aspect ratio. The correlation for the drop aspect ratio is proposed in terms of the Reynolds and Eötvös numbers in the ranges of 0.061 <Re < 342.59, 0.004 <Eo < 1.166, and (−4.756) < log10 (Mo) < (−9.171), respectively. Interfacial area of drop enhances with an increase in the dispersed volume phase and jet velocity. Empirical correlation is developed to predict Sauter mean drop diameter, drop aspect ratio, distribution function parameters, and interfacial area based on operating variables and physical properties of the system.

Dispersed-phase Volume Fraction and Flow Regimes in Oscillatory Liquid-Liquid Two-Phase Flow in Annuli: Comparison of Sieve-Plate and Baffle-Plate Internals

ABSTRACT Liquid-liquid two-phase flows are central to solvent extraction processes. In a columnar solvent extraction contactor, the turn-down ratio can be increased by imposing oscillatory flow over steady flow. This study compares dispersed phase volume fraction and flows regimes for oscillatory liquid-liquid two-phase flow in annuli having sieve-plate and baffle-plate internals. Such flows in annuli are important for specific solvent extraction applications requiring a high surface-to-volume ratio in the contactor geometry. For identical conditions, the volume fraction of the dispersed phase is found to be more in the annulus having baffle plates compared to the annulus having sieve plates. For both types of internals, an increase in dispersed phase velocity or continuous phase velocity, or oscillation velocity leads to enhancement in the volume fraction of the dispersed phase. The dispersed phase volume fraction increases when the spacing between sieve plates or baffle plates is reduced or when the fractional open area is reduced. Retention of the dispersed phase is more in the annulus having a smaller equivalent diameter. The annulus having baffle plates shows a faster transition from mixer-settler to dispersion regime or dispersion regime to the quasi-emulsion regime. Higher dispersed phase volume fraction in the annulus having baffle-plate internals suggests that it is more suitable for mass transfer than the annulus having sieve-plate internals. However, faster regime transitions in the annulus having baffle plates indicate that it is more prone to flooding than the annulus having sieve plates. The correlations that can be used to estimate the volume fraction of the dispersed phase are proposed. These correlations will be useful for design calculations.

Theoretical and numerical studies of the phase velocity of wakefields in plasma driven by self-modulated proton beams with electron beam seeding

Significant progress has been made in the studies of wakefield excitation in plasma by a self-modulated high energy proton beam in the past decade. The electron beams accelerated up to 2 GeV by using such a wakefield were demonstrated in the AWAKE experiment at CERN in 2018. Aiming at the application of high energy particle accelerators, new ideas have been investigated in recent years, such as seeding the proton beam self-modulation with an electron beam in order to enhance the strength and stability of the wakefield or adding a density transition in the plasma distribution to enhance the phase velocity and the strength of the wakefield. Here in this work, we investigate the effects of electron beam seeding on the phase velocity of the wakefield generated by the modulated proton beam in plasma. The physical mechanisms responsible for the phase velocity change and the roles played by the electron beam seeding are discussed. The theoretical analysis and two-dimensional particle-in-cell simulations show that both the growth rate and the phase velocity of the wakefield generated by the modulated proton beam can be enhanced by the electron beam seeding. The higher the charge density of the electron beam, the more significant the enhancement effects. The effects of electron beam energy and proton beam longitudinal profiles on the increase of phase velocity are also studied. It is shown that the evolution of the electron beam distribution has a significant effect on the seeding self-modulation process, and thus affecting the phase velocity. A self-focusing electron seeding beam can increase the phase velocity of the wakefield even to superluminal while an expanding seeding beam can reduce the phase velocity and destroy the stability of the whole process. This work may benefit the proton beam seeding self-modulation acceleration and its applications.

Investigation of microfluidic co-flow effects on step emulsification: Interfacial tension and flow velocities

We propose a novel chip combining co-flow and step emulsification for flexible on-line control of droplet generation. Through this technique, we obtain controllable uniformly sized water in oil droplets. The droplet diameter is controlled between 101 and 1550 μm and the generation frequency ranges from 0.32 to 100 Hz when using the new chip. Compared with conventional step emulsification, droplet dimension is reduced by more than 50% and throughput is increased up to a factor of 50 by using continuous phase co-flow within a certain range in the chip. We also simulate the effects of interfacial tension and flow velocities on emulsification. As continuous phase velocity increases, co-flow gradually replaces the Laplace pressure difference as the driving mechanism in step emulsification. Compared with step-emulsification, the effects of interfacial tension on droplet size and generation frequency greatly change when continuous phase co-flow is added. Co-flow causes both droplet diameter and generation frequency to increase with increasing dispersed phase velocity. Meanwhile, the driving mechanism changes from co-flow to Laplace pressure difference as the dispersed phase velocity increases, because of the increase in pinch-off distance. In addition, droplet generation changes from dripping to jetting as dispersed phase velocity increases. These effects of continuous phase co-flow on step emulsification are significant, and this technique can be easily used for tunable and high-throughput droplet production.