Averaged Dynamics of Fluids near the Oscillating Interface in a Hele-Shaw Cell

The steady flow in a Hele-Shaw cell filled with fluids with a high viscosity contrast in the presence of fluid oscillations is experimentally studied.The control of oscillatory dynamics of multiphase systems with interfaces is a challenging technological problem.We consider miscible(water and glycerol)and immiscible(water and high-viscosity silicone oil PMS-1000)fluids under subsonic oscillations perpendicular to the interface.Observations show that the interface shape depends on the amplitude and frequency of oscillations.The interface is undisturbed only in the absence of oscillations.Under small amplitudes,the interface between water and glycerol widens due to mixing.When the critical amplitude is reached,the interface becomes unstable to the fingering instability:Aqueous fingers penetrate the high-viscosity glycerol and induce intensive mixing of miscible fluids and associated decay of the instability.After the disappearance of the fingers,the interface takes a U-shape in the central part of the cell.A similar effect is observed for immiscible fluids:The oscillating interface tends to bend to the side of a high-viscosity fluid.Again,when the critical amplitude is reached,the fingering instability arises at the convex interface.This paper focuses on the causes of bending of the initially undisturbed interface between miscible or immiscible fluids.For this purpose,we measure the steady flow velocity near the interface and in the bulk of a high-viscosity fluid using Particle Image Velocimetry(PIV).

A new model for chromitite formation in ophiolites: Fluid immiscibility

Although the involvement of hydrous fluids has been widely invoked in formation of podiform chromitites in ophiolites, there is lack of natural evidence to signify the role and mechanism of fluids. In this study, a new model for the genesis of podiform chromitite is proposed on basis of revisits of comprehensive petrological, mineralogical and geochemical results of the well-preserved K?z?lda? ophiolite and the well-characterized Luobusa chromite deposit. In this model, ascending magmas intruding oceanic lithospheric mantle would presumably form a series of small magma chambers continuously connected by conduits. Tiny chromite nuclei would collect fluids dispersed in such magmas to form nascent droplets. They tend to float upward in the magma chamber and would be easily transported upward by flowing magmas. Chromite-rich droplets would be enlarged via coalescence of dispersed droplets during mingling and circulation in the magma chamber and/or transport in magma conduits. Crystallization of the chromite-rich liquid droplets would proceed from the margin of the droplet inward, leaving liquid entrapped within grains as precursor of mineral inclusions. With preferential upward transportation, immiscible chromite-rich liquids would coalesce to a large pool in a magma chamber. Large volumes of chromite would crystallize in situ, forming podiform chromitite and resulting in fluid enrichment in the chamber. The fluids would penetrate and compositionally modify ambient dunite and harzburgite, leading to significant fractionations of elemental and isotopic compositions between melts and fluids from which dunite and chromitite respectively formed. Therefore, fluid immiscibility during basaltic magma ascent plays a vital role in chromitite formation.

Origin of the Yueguang gold deposit in Xinhua, Hunan Province, South China: insights from fl uid inclusion and hydrogen–oxygen stable isotope analysis

The Yueguang gold deposit is located in Fengjia,Xinhua County,Hunan Province,South China.It represents a recently discovered small-scale gold deposit situated in the southwestern region of the Jiangnan Orogenic Belt,west of the Baimashan granitic batholith.In order to discern the characteristics of the ore-formingfluids,the underlying mineralization processes,and establish a foundation for the origin of the Yueguang gold depositfluid inclusion micro-thermometry,as well as quartz hydrogen and oxygen isotope analysis,have been carried out on samples obtained from various stages of mineralization.The hydrothermal miner-alization stages within the Yueguang gold deposit can be categorized into three stages:(i)the barren,pre-ore quartz-pyrite stage(Stage Ⅰ),the quartz-pyrite-gold stage(Stage Ⅱ),and the post-ore quartz-carbonate stage(Stage Ⅲ),with the second stage being the main mineralization stage.Thefluid inclusions identified in samples from the main min-eralization stage can predominantly be described with the NaCl–H_(2)O and CO_(2)–NaCl–H_(2)O systems.These inclusions display homogenization temperatures ranging from 158.8 to 334.9℃,and thefluid salinity ranges from 0.3%to 4.0%(wt.%NaCl equiv.).Laser Raman spectroscopy analysis of individual inclusions further reveals the presence of gas-phases such as CO_(2),CH_(4),and N_(2).Isotopic analysis indicatesδ^(18)Ofluid values ranging from 3.95 to 6.7‰ and δDH_(2)O values ranging from-71.9 to-55.7‰.These results indi-cate that the ore-formingfluid of the Yueguang gold deposit belongs to metamorphic hydrothermalfluids of middle-low temperature and low salinity.In the process of ore formation,gold is transported in the form of Au(HS)2-complexes,with gold deposition being driven byfluid immiscibility.Therefore,the Yueguang gold deposit is categorized as an orogenic gold deposit dominated by metamorphic hydrother-malfluid.It may become a new target for gold exploration in the Baimashan region,central Hunan Province.

Mathematical model of micropolar fluid in two-phase immiscible fluid flow through porous channel

This paper is concerned with the flow of two immiscible fluids through a porous horizontal channel. The fluid in the upper region is the micropolar fluid/the Eringen fluid, and the fluid in the lower region is the Newtonian viscous fluid. The flow is driven by a constant pressure gradient. The presence of micropolar fluids introduces additional rotational parameters. Also, the porous material considered in both regions has two different permeabilities. A direct method is used to obtain the analytical solution of the concerned problem. In the present problem, the effects of the couple stress,the micropolarity parameter, the viscosity ratio, and the permeability on the velocity profile and the microrotational velocity are discussed. It is found that all the physical parameters play an important role in controlling the translational velocity profile and the microrotational velocity. In addition, numerical values of the different flow parameters are computed. The effects of the different flow parameters on the flow rate and the wall shear stress are also discussed graphically.

The Solely Use of the “Hydraulic-Diameter” Concept Is Not Sufficient to Describe Correctly Non-Symmetric Flow in Conduits

A well-known cornerstone in fluid mechanics is the equations that relate the friction factor to the Reynolds number obtained from the measurements in cylindrical cross-sectional tubes. The extension of these equations to different geometries failed to give reliable results. The introduction of the Hydraulic Diameter has fixed this issue particularly for the square ducts. However, for non-symmetric flows, as in concentric annuli, the discrepancies were unacceptable. Several attempts have been made to fix these problems with finally the introduction of a new concept like, “Laminar Equivalent Hydraulic Diameter” or “Efficient Hydraulic Diameter” provided satisfactory results. This approach seems to have fixed the problem and hence has been widely accepted. Nevertheless, it is based on a non-robust theoretical argument. In the present paper, it has been demonstrated that the solely use of the “Hydraulic Diameter” concept is insufficient to describe non-symmetric flows as in concentric annuli. It appears the need to use the Z axis component of the skew driving force for the laminar flow and the parameter λ for the turbulent one. At the same time, instead, it has been shown that in the case of flow in square and rectangular ducts, the “Hydraulic Diameter” is sufficient to describe it. In this case, the flow is practically symmetric. Moreover, several new straightforward equations are provided, which simplify a lot dealing with non-cylindrical cross-sectional conduits. In doing so, the concept of “Eigenvectors-Eigenvalues” has been implemented. This theoretical approach could help to simplify other non-symmetric cases in fluid dynamics. To mention, “Flow past immersed non-symmetric bodies”, “Flow in curved conduits” etc.

Abundance of Carbonic Fluid Inclusions in Hira-Buddini Gold Deposit, Hutti-Maski Greenstone Belt, India: Inferences from Petrography and Volume Ratio Estimation of Fluid Components

Low saline aqueous carbonic fluids are considered to be the ore forming solutions for orogenic lode gold deposits.Phase separation/fluid immiscibility of the ore fluid is quite common and is one of the major reasons for deposition of gold in these deposits.Abundant carbonic fluid inclusions have been observed in quartz grains of Hira-Buddnini Gold Deposit.Theoretical estimation indicates that more volume of H2O compared to CO2 is likely to be trapped in inclusions at different P-T conditions.Preferential loss of H2O from fluid inclusions during ductile deformation of quartz grains have been attributed as the suitable reason for abundance of carbonic fluid inclusions.

Dynamics of Low-Viscosity Liquids Interface in an Unevenly Rotating Vertical Layer

The behavior of two immiscible low-viscosity liquids differing in density and viscosity in a vertical flat layer undergoing modulated rotation is experimentally studied.The layer has a circular axisymmetric boundary.In the absence of modulation of the rotation speed,the interphase boundary has the shape of a short axisymmetric cylinder.A new effect has been discovered,under the influence of rotation speed modulation,the interface takes on a new dynamic equilibrium state.A more viscous liquid covers the end boundaries of the layer in the form of thin films,which have the shape of round spots of almost constant radius;with increasing amplitude of the velocity modulation,the wetting boundary expands.It is found that upon reaching the critical amplitude of oscillations,the film of a viscous liquid loses stability,and the outer edge of the wetting spot collapses and takes on a feathery structure.It is shown that this threshold is caused by the development of the Kelvin-Helmholtz oscillatory instability of the film.The spreading radius of a spot of light viscous liquid and its stability are studied depending on the rotation rate,amplitude,and frequency of rotation speed modulation.The discovered averaged effects are determined by different oscillatory interaction of fluids with the end-walls of the cell,due to different viscosities.The effect of films forming can find application in technological processes to intensify mass transfer at interphase boundaries.

Instantaneous deformation characteristics of a single bubble in immiscible fluids

The passage of a rising bubble through immiscible fluids is encountered in bath smelting.In order to investigate characteristics of bubble deformation in immiscible fluids,the bubble shape change at the interface and the relationship between the bubble aspect ratio(E)and dimensionless number of forces were obtained.A three-dimensional model was established,and the free-floating behavior of a single bubble in immiscible fluids was numerically simulated by phase-field method.The simulation results are in good agreement with experimental results.The results indicate that when the bubble passes through the interface,the bubble shape is divided into four types in turn:“pear”,inverted“pear”,“convex”and“droplet”shape.In the lower liquid,the relationship of E to Weber number(We),Tadaki number(Ta),and Reynolds number(Re)is distributed between two intersecting lines.The relationship of E to Eötvös number(Eo),a dimensionless group,and Galilei number(Ga)is distributed near the lines with slopes of−3.325×10^(-5),−0.0855,and−8.73×10^(-4),respectively.In the upper liquid,the relationship of E to We,Ta,and Re is distributed between two parallel lines.Compared with gravity,the inertial force plays a leading role in the bubble shape in the lower and upper liquid.Compared with the viscous force,the surface tension dominates the bubble shape in the lower liquid.

Interface profile evolution between binary immiscible fluids induced by high magnetic field gradients

A mechanical analysis is done to find the evolution of the interface profile between binary immiscible fluids induced by a three-dimensional orthogonal magnetic field gradient.In the experiments,the changes of the interface profile between four groups of binary immiscible fluids are investigated under the same horizontal magnetic field gradients.The binary immiscible fluids are made of benzene and other liquids,like CuSO4,Fecl3,FeSO4 or Cucl2 aqueous solutions.In addition,the interface profile between the benzene and CuSO4 aqueous solution is examined under different horizontal magnetic field gradients.The experimental results are consistent with the theoretical analysis.This study explains the enhanced Moses effect from a mechanics standpoint.Furthermore,a new method for susceptibility measurement is proposed based on this enhanced Moses effect.

Cavity dynamics of water drop impact onto immiscible oil pool with different viscosity

In this work,we numerically study the impact of a water droplet onto a deep oil pool.Two fluids are immiscible and the viscosity of the pool liquid is changed systematically.We focus on the cavity dynamics during the impact and especially the effects of the pool liquid viscosity and the impacting velocity.For the parameter range explored,we identify the regime where splashing occurs with corolla breaking into droplets,and the regime where no splashing is observed.Similarity is found for the time evolution of cavity depth for fixed impact velocity and different viscosity,if the cavity depth and time are nondimensionalized by the maximal depth and the time when the maximal depth is reached.Effective power-law scalings are also proposed to describe the dependence of the maximal cavity depth and the corresponding time on the impact velocity and pool liquid viscosity,in the term of Froude and Reynolds numbers.