Immiscible Fluids Research Articles

High-Throughput Capillary Liquid Chromatography Using a Droplet Injection and Application to Reaction Screening.

The cycle time of a standard liquid chromatography (LC) system is the sum of the time for the chromatographic run and the autosampler injection sequence. Although LC separation times in the 1-10 s range have been demonstrated, injection sequences are commonly >15 s, limiting throughput possible with LC separations. Further, such separations are performed on relatively large bore columns requiring flow rates of ≥5 mL/min, thus generating large volumes of mobile phase waste when used for large scale screening and increasing the difficulty in interfacing to mass spectrometry. Here, a droplet injector system was established that replaces the autosampler with a four-port, two-position valve equipped with a 20 nL internal loop interfaced to a syringe pump and a three-axis positioner to withdraw sample droplets from a well plate. In the system, sample and immiscible fluid are pulled alternately from a well plate into a capillary and then through the injection valve. The valve is actuated when sample fills the loop to allow sequential injection of samples at high throughput. Capillary LC columns with 300 μm inner diameter were used to reduce the consumption of mobile phase and sample. The system achieved 96 separations of 20 nL droplet samples containing 3 components in as little as 8.1 min with 5-s cycle time. This system was coupled to a mass spectrometer through an electrospray ionization source for high-throughput chemical reaction screening.

Immiscible Rayleigh–Taylor turbulence: Implications for bacterial degradation in oil spills

An unstable density stratification between two fluids mixes spontaneously under the effect of gravity, a phenomenon known as Rayleigh-Taylor (RT) turbulence. If the two fluids are immiscible, for example, oil and water, surface tension prevents intermixing at the molecular level. However, turbulence fragments one fluid into the other, generating an emulsion in which the typical droplet size decreases over time as a result of the competition between the rising kinetic energy and the surface energy density. Even though the first phenomenological theory describing this emulsification process was derived many years ago, it has remained elusive to experimental verification, hampering our ability to predict the fate of oil in applications such as deep-water spills. Here, we provide the first experimental and numerical verification of the immiscible RT turbulence theory, unveiling a unique turbulent state that originates at the oil-water interface due to the interaction of multiple capillary waves. We show that a single, non-dimensional, and time-independent parameter controls the range of validity of the theory. Our findings have wide-ranging implications for the understanding of the mixing of immiscible fluids. This includes in particular oil spills, where our work enables the prediction of the oil-water interface dynamics that ultimately determine the rate of oil biodegradation by marine bacteria.

Experimental investigation of propagation evolution characteristics of internal solitary waves passing through downslope topography

In contrast to the extensive research on the propagation evolution of internal solitary waves (ISWs) over continental shelf topography, few investigations have been conducted on the propagation evolution of ISWs over downslope topography. In this experiment, the characteristics of the ISWs passing over a downslope topography were investigated in an immiscible two-layer fluid system to clearly capture the waveform information. The main objective of this study was to analyze the propagation evolution of ISWs with different incident amplitudes passing through a downslope topography. Using the particle image velocimetry technique, the evolutionary characteristics of ISWs (such as waveform, wave height, energy budget, and flow field) are investigated. According to the flow field analysis results, the phase velocity near the downslope topography changes with the propagation of ISWs. Moreover, the gradient distribution of velocity progressively becomes perpendicular to the right surface of the topography. Furthermore, a counterclockwise vortex gradually forms at the right upper vertex of the topography. The propagation of ISWs is influenced by varying water depth and topography. The front waveform of ISWs is significantly flat, and the back is steeper than the original back waveform. Around the tail wave, an upward convex wave packet is generated. The trends of wave energy and wave height losses are broadly consistent. Furthermore, the energy loss is related to the incident wave height with a 20% higher loss rate for large-amplitude ISWs than small-amplitude ISWs at the inflection point of the topography.

Fluid–structure-interactive elasto- and thermo-hydrodynamics of electrokinetic binary fluid flows in compliant micro-confinements

We explore the intricate two-way fluid structure interaction arising due to the flow of a binary system of immiscible Newtonian fluids, composed of upper electrically conducting and lower electrically insulating fluids, flowing within a compliant microchannel, whose walls behave as linear elastic solids. The transport of the fluids along the domain occurs due to the collective impact of pressure gradient and applied electric field. We solve the closed-form system of equations and obtain semi-analytical expressions for the velocity fields and channel wall deformation from the coupled elasto-hydrodynamic problem. We then delineate the effect of four pivotal parameters: (a) Debye–Hückel parameter κ¯, (b) upper wall slip length, ls¯, (c) viscosity ratio, μr, and (d) elasticity ratio, Nr, on the morphological evolution of the wall deformation characteristics and the spatial distribution of the velocity profile of the fluids. Observations establish a positive co-relationship of wall deformation with fluid pressure, showcasing an increased collapsibility with augmented pressure gradients. Consequently, the channel walls show enhanced deformation with a decrease in κ¯, ls¯, μr and with an increase in Nr. We also demonstrate from our model that by properly tuning the applied pressure gradient and electric field, it is possible to achieve counterflow of the two fluids. We also consider the effect of heat generation in the fluids due to viscous dissipation and Joule heating, which dissipates to the surrounding by the mechanism of conjugate heat transfer. Accordingly, we provide semi-analytical expressions for the temperature profile distribution within the channel, and discuss their variation with three thermo-physical parameters: (a) Biot number of the top wall (Bi1), (b) Peclet number of the top fluid (Pe1), and (c) ratio of the thermal conductivities of the upper conducting fluid to that of the upper solid wall (kr2). We establish from our investigation that with the increase in Pe1 and with the decrease in Bi1 and kr2, the overall system temperature enhances. Finally, in order to design a thermally efficient system, we compute the global entropy generation rate in the system and evaluate optimum values of, Pe1, Bi1, and kr2 for which the system exhibits highest second law efficiency. We expect our findings to contribute toward the development of optimized microfluidic devices fabricated from deformable elastic materials.

A practical guide to mitigate edge fracture instability in sheared polymer melts

The measurement of nonlinear shear response of viscoelastic materials is often hindered by edge fracture instabilities. The phenomenon was first addressed theoretically by Tanner and Keentok and ever since has attracted the interest of experimentalists and theorists alike. Despite progress, accounting for or mitigating edge fracture remains a challenge, in particular when dealing with strongly viscoelastic materials such as entangled polymer melts. Here, we present and compare different experimental attempts to delay edge fracture in a cone-and-plate (CP) geometry, including the use of an immiscible fluid bath around the sample (that reduces the stress and interfacial gradients in comparison with the sample/air interface), a cone-partitioned plate (CPP) fixture, and an outer collar attached to the sample's edge (in a CP or CPP fixture). Focusing on the torque signal, we find that the combination of CPP and collar provides the best results. This may indeed help measuring highly elastic materials over an extended range of shear rates and, importantly, contribute to reliably measuring the normal stress coefficients in a cone-partitioned plate tool. It is, therefore, hoped that this simple idea will be further pursued in the direction of improving our current rheometric capabilities.

Dynamics of a two-layer immiscible fluid system exposed to ultrasound.

The relocation dynamics of a two-layer immiscible fluid system exposed to bulk acoustic waves using simulations and experiments are reported. A theoretical formulation of the acoustic radiation pressure (ARP) acting on the interface reveals that ARP is a nonlinear function of the impedance contrast. It has been shown that the force acting on the interface is the simple sum of the ARP and the interfacial tension, which is dependent on the angle of the interface. It was discovered that although the acoustic radiation force is directed from high-impedance fluid (HIF) to low-impedance fluid (LIF), the final steady-state configuration depends on the wall-fluid contact angle (CA). Our study reveals that the HIF and LIF would relocate to the channel center for CA>110°, and CA<70°, respectively, while complete flipping of the fluids is observed for intermediate angles. The forces relocate the fluids in the channel, generally, by a clockwise or anticlockwise rotation. Here, it is demonstrated that the direction of this twist can be determined by the relative densities and wettabilities of the two fluids.

A multi-region and a multiphase MHD OpenFOAM solver for fusion reactor analysis

Several systems in nuclear fusion reactors utilize liquid metals as working fluids and the design of these systems cannot overlook the magnetohydrodynamics effects arising from the interaction between the electrically conductive fluid and the magnetic fields used to confine the plasma, since these effects significantly influence the flow features. In this context, rigorous studies and research activities are imperative to provide high–quality numerical data and develop precise predictive numerical tools. This work introduces two OpenFOAM magnetohydrodynamics solvers and outlines their respective validation processes. The mMRF solver can simulate single–phase, incompressible MHD flow for multiple electro–coupled domains. Meanwhile, the mIF solver is capable of simulating two–phase MHD flow involving incompressible and immiscible fluids. The mMRF solver has demonstrated outstanding results in simulating classical 2D benchmarks up to high magnetic field intensities, while the mIF solver proved its ability by estimating, with a discrepancy of less than 10%, the velocity of a bubble rising within a liquid metal under an imposed magnetic field.

Numerical study of the Marangoni effect induced by soluble surfactants and solute based on rising droplets

In this study, we present a numerical investigation into the phenomenon of rising droplets in immiscible fluids, focusing on the Marangoni effect induced by both solute and a combination of solute and soluble surfactants. We meticulously examine the interfacial behaviors of pure solute droplets and mixed droplets, with a particular interest on the intricate interplay among interfacial concentration, interfacial tension, Marangoni stress, and Marangoni convection. Our investigation provides insight into the influence of key physicochemical parameters, such as viscosity, diffusion coefficient, partition coefficient, and interfacial tension gradient, on the Marangoni instability. Furthermore, we conduct a comprehensive parametric exploration of the impact of dimensionless numbers such as the Langmuir number (La), the Damkohler number (Da), the Peclet number (Pe), and the elasticity number β on the stabilizing efficacy of surfactants. The research findings underscore the effectiveness of our numerical method in capturing the distinctive two-step acceleration characteristics of pure solute droplets and the stabilizing effect of surfactants on mixed droplets. Notably, our study reveals that the Marangoni instability may manifest even when the viscosity and diffusivity ratios of the two-phase fluids are closely matched. Partition coefficients below unity exhibit only a marginal influence on the re-acceleration time of the droplets. Systems characterized by extremely low interfacial tension gradients tend to exhibit no Marangoni instability. Moreover, an increase in La enhances the stability of mixed droplets, while a significant threshold is identified for Da to affect the stability of mixed droplets. The ascent speed of mixed droplets displays pronounced variation across varying Pe magnitudes. Finally, in scenarios involving a wide-ranging variation in β, mixed droplets transition between the states of pure solute droplets and rigid spheres, revealing a distinct-state transition point.

Effect of shock impedance of mesoscale inclusions on the shock-to-detonation transition in liquid nitromethane

Two-dimensional, meso-resolved numerical simulations are performed to investigate the effect of shock impedance of mesoscale inclusions on the shock-to-detonation transition (SDT) in liquid nitromethane (NM). The shock-induced initiation behaviors resulting from the cases with NM mixed with randomly distributed, 100-μm-sized air-filled cavities, polymethyl methacrylate (PMMA), silica, aluminum (Al), and beryllium (Be) particles with various shock impedances are examined. In this paper, hundreds of inclusions are explicitly resolved in the simulation using a diffuse-interface approach to treat two immiscible fluids. Without using any empirically calibrated, phenomenological models, the reaction rate in the simulations only depends on the temperature of liquid NM. The sensitizing effect of different inclusion materials can be rank-ordered from the weakest to the strongest as PMMA → silica → air → Al → Be in the hot-spot-driven regime of SDT. Air-filled cavities have a more significant sensitizing effect than silica particles, which is in agreement with the experimental finding. For different solid-phase inclusions, hot spots are formed by Mach reflection upon the interaction between the incident shock wave and the particle. The sensitizing effect increases roughly with the shock impedance of the inclusion material. More details of the hot-spot formation process for each solid-phase inclusion material are revealed via zoom-in simulations of a shock passing over a single particle.

Thermo-capillarity of immiscible binary fluids within serpentine micro-confinements

The thermocapillary flow of multiple liquid layers over contoured substrates finds applications in many industrial phenomena via micro-electromechanical systems/nano-electromechanical systems devices. This study theoretically explores the thermocapillary transport of binary-liquid layers in a wavy microchannel with serpentine wall profiles. Sinusoidal profiles are considered for the microchannel walls' temperature and surface topology. Patterned slip conditions at the walls are also accounted for in the analysis to make the problem more realistic. We semi-analytically solve the energy and momentum equations to understand the system's thermal and hydrodynamic characteristics for the limiting conditions of Ma, Re, and Ca. The leading- and higher-order solutions of the temperature and flow field are separately shown to demonstrate the advection terms' contribution to the transport equations. The circulatory flow obtained due to periodic thermal stimuli can be used to enhance the mixing efficiency of the system. We also present how the parameters like phase difference between the thermal stimulus, relative thermal conductivity, and relative film thickness ratio of the liquid layers can be altered to control the flow characteristics to obtain the most potent thermocapillary effect.

Controlling viscous fingering instabilities of complex fluids

Despite their aesthetic elegance, wavy or fingering patterns emerge when a fluid of low viscosity pushes another immiscible fluid of high viscosity in a porous medium, producing an incomplete sweep and hampering several crucial technologies. Some examples include chromatography, printing, coating flows, oil-well cementing, as well as large-scale technologies of groundwater and enhanced oil recovery. Controlling such fingering instabilities is notoriously challenging and unresolved for complex fluids of varying viscosity because the fluids’ mobility contrast is often predetermined and yet the predominant drive in determining a stable, flat or unstable, wavy interface. Here we show, experimentally and theoretically, how to suppress or control the primary viscous fingering patterns of a common type of complex fluids (of shear-thinning with a low yield stress) using a radially tapered cell of linearly varying gap thickness, h(r). Experimentally, we displace a complex viscous (PAA) solution with gas under a constant flow rate (Q), varied between 0.02 and 2 slpm (standard liter per minute), in a radially converging cell with a constant gap-thickness gradient, α=dh/dr<0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha = dh/dr < 0$$\\end{document}. A stable, uniform interface emerges at low Q and in a steeper cell (i.e., greater |α|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|\\alpha |$$\\end{document}) for the complex fluids, whereas unstable fingering pattern at high Q and smaller |α|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|\\alpha |$$\\end{document}. Our theoretical predictions with a simplified linear stability analysis show an agreeable stability criterion with experimental data, quantitatively offering strategies to control complex fluid-fluid patterns and displacements in microfluidics and porous media.

Thermo-Fluidic Analysis of Pulsating Heat Pipes Charged with Water-Based Immiscible Fluid Pairs

Immiscible fluids may provide operational flexibility for pulsating heat pipes (PHPs) due to thermo-hydrodynamic diversity lead by each pure component. In this regard, present paper focuses on the thermo-fluidic analysis of non-uniform pulsating heat pipes charged with water-based immiscible fluid pairs. Research parameters cover gravity effect via the inclination angles (IA) of 0o and 90o, and fluid pair effect via two different water-based immiscible binary fluids as Water (W) – Hexane (H), and Water (W) – Pentane (P). The volumetric mixing ratios are W:H=1:1, 1:4, 4:1, 1:0, 0:1, and W:P=1:1, 1:4, 4:1, 1:0, 0:1; and the non-uniform flat plate type pulsating heat pipe (FP-CLPHP) has alternating-sequence parallel channels. The experiments are performed at the filling ratio of 40% (FR=40%), and flow phenomena is visualized. As some conclusions; at vertical orientation, the FP-CLPHPs having binary fluids of water-pentane show better thermal performance compared to the pure counterparts. Especially, the heat transfer characteristics of W:P=1:1 are the best ones among all the pure and binary fluids. On the other hand, as a conclusion of combination of non-uniform design and suitable thermophysical properties, the FP-CLPHPs charged with pure pentane, pure hexane or binary fluid of W:P=1:4 can work independent from gravitational force.

Increasing Oil Recovery by Varying Surfactant Concentrations and Expanding the Well Drainage Area

Surfactant flooding plays a crucial role in advanced techniques for boosting oil recovery. There remains a significant volume of unrecovered oil in reservoirs, particularly in carbonate reservoirs. These reservoirs often face challenges with low primary and water-flood recovery due to inadequate sweep efficiency, resulting in the presence of bypassed or trapped oil. Chemical flooding approaches, including surfactant flooding, have demonstrated their effectiveness in the retrieval of this trapped oil. The fundamental concept of surfactant flooding involves injecting a surface-active agent, known as a surfactant, to reduce the interfacial tension and mobilize the residual oil saturation. Surfactants have been widely utilized for various purposes in the petroleum industry since its early years, owing to their capacity to modify interfacial interactions between two immiscible fluids in contact with one another. Interfacial phenomena play a significant role in rock-fluid interactions and the interactions between fluids from the reservoir to distribution pipelines. Consequently, surfactants find application in a variety of activities within the petroleum industry. Laboratory experiments, pilot-scale projects, and field-scale initiatives worldwide have yielded diverse outcomes regarding the use of surfactants for enhancing oil recovery. Multiple types of surfactants have been investigated to determine highly effective chemical formulations for enhanced oil recovery, with anionic and non-ionic surfactants being commonly employed in sandstone reservoirs.

Fractal patterns in fluid flows: A radial basis pseudospectral analysis of CuO-EG water nano, Saffman dusty, and plain Newtonian fluids in immiscible layers of a horizontal channel

Nano and dusty fluids provide new possibilities to improve energy transfer efficiencies. Motivated by immiscible fluids duct flow framework in the filtration of hydrocarbon materials, the objective of this manuscript is to present the numerical study of three immiscible fluids namely, copper oxide-ethylene glycol (CuO-EG) water nano, Saffman dusty, and plain Newtonian fluids in the horizontal channel. For the formulation of the mathematical model, the dusty fluid is positioned between the immiscible layers of the nanofluid and Newtonian fluid. The interface between the immiscible fluids is continuous and non-deformable in nature. The flow is driven by an externally time-dependent pressure gradient. The novel radial basis function pseudospectral (RBFPS) method is employed to solve the governed partial differential equations, and the resulting outcomes are compared with cubic B-spline differential quadrature and finite difference method. The impact of several crucial fluid parameters, comprising the volume percentage of CuO nanoparticles, the dust particle concentration parameter, and various others on velocity profiles, are presented graphically. It is observed that despite being present only in the lower zone, the CuO nanoparticles have an impact on the flow velocities in other zones also. The fluid and particle velocities decrease as the volume fraction of CuO increases.

Simulation of collision behaviour between droplet and solid surface in liquid phase environment

AbstractProcesses involving dispersed immiscible fluids occur across the traditional onshore and offshore crude oil development phases, including oil exploitation and production, gathering and transportation, and station and field processing. The stabilities of such processes are deeply influenced by the collision and film drainage between separated phase interfaces. Due to factors such as gravity as well as buoyancy and resistance, droplets usually collide with the wall at a relatively high speed and experience one or several rebounds before gradually stabilizing and staying on the surface. Though work related to this aspect has raised significant attention, further research on the force‐deformation behaviour between microsized (r ≈50 μm) droplets and solid surface under the influence of the above factors is still lacking and strongly demanded. In this paper, under the comprehensive influence of flow driving, an emulsified water droplet colliding with a solid surface in silicon oil is modelled. The dynamic behaviour of the droplet was analyzed by coupling the Stokes–Reynolds drainage equation, the generalized Young–Laplace equation, and the force situation of the deformable droplet. Furthermore, the effects of interfacial tension, collision velocity, and viscosity of continuous phase on the collision characteristics of droplet were analyzed, and it was found that these factors could significantly change the collision characteristics of droplet.

Reaction path model of the formation of abiotic immiscible hydrocarbon fluids in subducted carbonated serpentinites, Lanzo Massif (Western Italian Alps)

Fluids generated from subducted slabs participate in the cycling of deep carbon in the crust and upper mantle. In these fluids, aqueous carbon species vary in oxidation state between +IV and -IV depending on whether the fluids are oxidizing or reducing, respectively. Most studies of subduction-zone fluids have focused on oxidized carbon species. However, recent studies of natural samples have demonstrated the occurrence of deep, reducing fluids, generated in both subducted oceanic upper mantle and crustal rocks. CH4-H2-rich fluid inclusions in subducted carbonated serpentinites have demonstrated the existence of abiotic, immiscible, hydrocarbon fluids at upper mantle conditions. To investigate the formation of such immiscible hydrocarbon fluids during the evolution of subducted carbonated serpentinites, we used equilibrium constants from the Deep Earth Water model to carry out predictive chemical mass transfer modeling to simulate the alteration reactions. A novel feature of the models was the inclusion of an immiscible hydrocarbon fluid containing six components (CH4,f,C2H6,f,C3H8,f,isoC4H10,f,CO2,f,H2,f). This feature enabled prediction of the formation of a separate immiscible fluid in equilibrium with aqueous species and minerals.We developed a predictive reaction path model of invasive H2,f reacting with carbonated serpentinites and interstitial aqueous fluids for comparison with the natural samples from the Lanzo Massif, western Italian Alps. Over a range of temperatures and pressures, immiscible hydrocarbon fluids formed in association with altered mineral assemblages. Reaction progress caused the transformation of carbonated serpentinites and the formation of clinopyroxene, brucite, graphite, and hydrocarbon fluids, along with changes of pH, logfO2, and aqueous species. CH4,f was the most abundant hydrocarbon species in all the models. The overall results at 2.0 GPa and 400 to 450 °C were consistent with the natural samples from the Lanzo Massif. Interestingly, large amounts of H2O formed due to oxidation of H2. More hydrocarbons and H2O formed in models with lower fluid/rock mass ratios or with more reactant H2. Models at different pressure and temperature conditions showed similar results with some variation in the relative stabilities of aragonite, graphite and olivine solid solution, and associated differences in mineral sequences, hydrocarbon fluids, values of aqueous species, and the final logfO2 and pH. Our models strongly support the laboratory and field evidence that reduction of carbonated serpentinites by infiltrating H2 fluids can cause the formation of immiscible, abiotic hydrocarbon fluids in subduction zones.

Nature, source, and evolution of the ore-forming fluids in the Dunbasitao gold deposit, East Junggar, China: Constraints from geology, fluid inclusions, and C-H-O isotopes

The origin of CO2-dominated fluids in orogenic gold deposits is usually mired in controversy. The Dunbasitao gold deposit is the largest among several gold deposits along the Armantai suture zone, East Junggar, China. Orebodies are hosted in volcano-sedimentary rocks of the Lower Carboniferous Jiangbasitao Formation and porphyritic quartz diorite and are controlled by shear zones. Based on the cross-cutting relationship of veins, the hydrothermal process can be divided into the early, middle, and late stages and the gold only occurred in the middle stage. Seven types of fluid inclusions (FIs) were identified in the Dunbasitao deposit: Type-1 FIs (LH2O + LCO2 or LH2O + LCO2 + VCO2) that homogenized to H2O phase or show critical homogenization; Type-2 FIs (LH2O + LCO2 or LH2O + LCO2 + VCO2) that homogenized to CO2 phase; CO2-dominated Type-3 FIs (LCO2 or LCO2 + VCO2); Two-phase aqueous Type-4 FIs (LH2O + VH2O) that homogenized to liquid phase; Type-5 FIs are composed of three phases (LH2O + VH2O + Solid), which homogenized to liquid phase; Type-6 and Type-7 FIs refers to FIs composed of a single liquid or vapor H2O phase, respectively.Microthermometry and laser Raman spectroscopy (LRS) analyses show that the initial ore-forming fluids in the early stage were moderate-Th (326–342 °C), low salinity (2.4 to 4.7 wt% NaCl equiv), and homogenous H2O−CO2−NaCl liquid fluids, containing 13–33 mol% CO2 and a small amount of CH4, H2S, and N2. The calculated δ18OH2O (V-SMOW) values are 7.5–8.5 ‰, δ18DH2O (V-SMOW) values range from −100 to −96 ‰, and δ13Cfluid (PDB) range from −3.8 to −2.5 ‰. In the middle stage, two typical immiscible fluid inclusion assemblages (FIA.18 and FIA. 27) composed of both Type-1 and Type-2 FIs were measured. The salinity of FIA.18 is 3.3 wt% NaCl equiv. and Th is 320 °C. For FIA.27, the salinity is 2.2 wt% NaCl equiv. and Th is 298 °C. The salinities of Type-4 FIAs vary from 5.9 to 14.4 wt% NaCl equiv., significantly higher than Type-1 and Type-2 FIs (1.7 to 3.5 wt% NaCl equiv). The salinities of three isolated Type-5 FIs (halite-bearing) range from 30.3 to 32.9 wt% NaCl equiv. and Th vary from 257 to 277 °C. These facts indicate extreme unmixing between carbonic and aqueous fluids in the middle stage, which led to gold precipitation. The Type-3 FIs represent the salt-free, H2O-lost, CO2 end-member composition, whilst the Type-5 FIs and high-salinity Type-4 FIs represent the highly saline aqueous end-member composition. Late-stage fluids are initially liquid, very low-salinity (1.4 to 2.6 wt% NaCl equiv), and low-Th (176–233 °C) aqueous fluids.Two immiscible carbonic FIAs from the middle stage yield a trapping pressure (Pt) of 86.9–133.9 MPa. Considering the rapid pressure fluctuations during fluid immiscibility, using hydrostatic or lithostatic pressure alone cannot get the real mineralization depth, Therefore, we use the lithostatic pressure for the Pt maximum and hydrostatic pressure for the Pt minimum and calculated a mineralization depth of 5.3–8.9 km, which doesn't represent the change but uncertainty for depth. Combining the characteristics of ore-forming fluids with the hydrothermal alteration and mineral compositions of ores, the Dunbasitao gold deposit is determined as a mesozonal orogenic gold deposit and there is considered to be prospecting potential in the deep.

Research on the Influence of Heterogeneity and Viscosity on the Fluid Intrusion Mechanism of the Water Flooding Process Based on the Microscopic Visualization Experiment.

The flow law of immiscible fluids in porous media plays an important role in the development of oil and gas fields. In the process of water flooding reservoir development, when the water phase displaces the oil phase, a fluid with higher viscosity, as a fluid with lower viscosity, the oil-water interface will always be unstable, resulting in different fingering effects. After water flooding, the distribution law of oil and water in the reservoir is mainly affected by the fluid intrusion mechanism. Due to the difference of capillary force, viscous force, and other microscopic forces, the fluid intrusion mechanism is mainly divided into two types: viscous fingering and capillary fingering. At the same time, due to the influence of reservoir heterogeneity, the fingering effect in the process of water displacement in porous media will be influenced to a certain extent. Based on the two-dimensional microscopic visualization experiment, this paper extracted the variance of the static parameter G in the capillary number calculation method of the two-dimensional microscopic model to represent the heterogeneity and conducted displacement experiments with different viscosities and flow rates to study the influence of the flow rate, viscosity, and heterogeneity on the results of water flooding. The experiments found that as for the influence of flow velocity, with the increase of flow velocity, that is, with the increase of capillary number, the recovery degree decreases first and then increases. As for the influence of viscosity, from a numerical point of view, the displacement efficiency and conformance coefficient of the low-viscosity group are higher than those of the high-viscosity group. From the trend, with the increase of the capillary number, the displacement efficiency of both the low-viscosity and high-viscosity groups increases, while the conformance coefficient decreases first and then increases, indicating that capillary fingering and viscous fingering can occur in different viscosity reservoirs. As for the influence of heterogeneity, the conformance coefficient of the water flooding decreases with the increase of heterogeneity, and the viscous pointing trend caused by heterogeneity is stronger, resulting in an uneven water injection sweep and higher oil displacement efficiency within the swept area. It can be seen from the fluid intrusion mechanism diagram that with the increase of heterogeneity, the viscous fingering trend becomes more obvious; with the increase of viscosity, the fluid intrusion mechanism boundary moves down and the viscous fingering trend becomes more obvious.

Evolution dynamics of thin liquid structures investigated using a phase-field model.

Liquid structures of thin-films and torus droplets are omnipresent in daily lives. The morphological evolution of liquid structures suspending in another immiscible fluid and sitting on a solid substrate is investigated by using three-dimensional (3D) phase-field (PF) simulations. Here, we address the evolution dynamics by scrutinizing the interplay of surface energy, kinetic energy, and viscous dissipation, which is characterized by Reynolds number Re and Weber number We. We observe special droplet breakup phenomena by varying Re and We. In addition, we gain the essential physical insights into controlling the droplet formation resulting from the morphological evolution of the liquid structures by characterizing the top and side profiles under different circumstances. We find that the shape evolution of the liquid structures is intimately related to the initial shape, Re, We as well as the intrinsic wettability of the substrate. Furthermore, it is revealed that the evolution dynamics are determined by the competition between the coalescence phenomenology and the hydrodynamic instability of the liquid structures. For the coalescence phenomenology, the liquid structure merges onto itself, while the hydrodynamic instability leads to the breakup of the liquid structure. Last but not least, we investigate the influence of wall relaxation on the breakup outcome of torus droplets on substrates with different contact angles. We shed light on how the key parameters including the initial shape, Re, We, wettability, and wall relaxation influence the droplet dynamics and droplet formation. These findings are anticipated to contribute insights into droplet-based systems, potentially impacting areas like ink-jet printing, drug delivery systems, and microfluidic devices, where the interplay of surface energy, kinetic energy, and viscous dissipation plays a crucial role.

EXPERIMENTAL INVESTIGATION OF SECONDARY FLOW DURING THE DROPLET FORMATION IN THE FLOW-FOCUSING CHANNEL

In this study, we have investigated the complex dynamics of droplet formation in a flow-focusing channel. Experiment has been performed under micro-particle image velocimetry (&amp;mu;PIV). The growth of droplets has been observed at four stages: lagging, filling, necking, and detachment. The interaction of two immiscible fluids, de-aerated water and silicon oil, is used. Characteristics of the droplet thread have been analyzed. Length of dispersed thread and tip size decrease with increased flow rate ratio. Furthermore, the flow characteristics of the dispersed phase, the velocity fields, contour plots of vorticity (&amp;omega;&lt;sub&gt;z&lt;/sub&gt;) swirl strength (&amp;lambda;&lt;sub&gt;1&lt;/sub&gt;), and circulation strength (Г/U&lt;sub&gt;d&lt;/sub&gt;W) have been investigated. Vortex flow region is identified during the droplet formation in such flow conditions (Re &amp;#126; 1 and Ca &amp;#60; 0.01). The vortex flow region shrinks with increasing flow rate ratio. Our experimental methodology and results have illustrated the presence of a temporal vortex pair during droplet formation in dispersed phase, a phenomenon with potential to amplify the chaotic mixing of multiphase fluids in a microchannel.