Numerical study of interface tracking for the unsteady flow of two immiscible micropolar and Newtonian fluids through a horizontal channel with an unstable interface

The dynamics of the interaction between immiscible fluids is relevant to numerous complex flows in nature and industry, including lubrication and coating processes, oil extraction, physicochemical separation techniques etc. In this article, the unsteady flow of two immiscible fluids i.e. an Eringen micropolar and Newtonian liquid, is considered in a horizontal channel. Despite the no-slip and hyper-stick boundary conditions at the channel wall, it is accepted that the fluid-fluid interface is unstable, and it travels from one position to another, and may even be deformed; hence the single momentum equation in the volume of fluid (VOF) method is combined with the continuum surface approach model to track the interface. The immiscible fluids are considered to flow under three applied pressure gradients (constant, decaying and periodic) and flow is analyzed under seamless shear stress over the entire interface. The modified cubic b-spline differential quadrature method (MCB-DQM) is used to solve the modeled coupled partial differential equations for the fluid interface evolution. The advection and tracking of the interface with time, wave number, and amplitude are illustrated through graphs. It is observed that the presence of micropolar parameters affects the interface with time. The novelty of the current study is that previous studies (which considered smooth and unstable movement of the micropolar fluid, the steady stream of two immiscible fluids and interface monitoring through different modes) are extended and generalized to consider unsteady flow of two immiscible Eringen micropolar and Newtonian fluids with a moving interface in a horizontal channel. For the decaying pressure gradient case, which requires more time to achieve the steady state, the peak of the waves resemble those for the constant pressure gradient case. The interface becomes steady for a more extensive time when a constant pressure gradient is applied. The interface becomes stable quickly with time as the micropolar parameter is decreased for the constant pressure gradient case i.e. weaker micropolar fluids encourage faster stabilization of the interface. With periodic pressure gradient, the interface takes more time to stabilize, and the crest of the waves is significantly higher in amplitude compared to the constant and decaying pressure cases. The simulations demonstrate the excellent ability of MCB-DQM to analyze complex interfacial immiscible flows

Ion slip and hall effects on generalized time-dependent hydromagnetic Couette flow of immiscible micropolar and dusty micropolar fluids with heat transfer and dissipation : a numerical study

The hydrodynamics of immiscible micropolar fluids are important in a variety of engineering problems, including biofluid dynamics of arterial blood flows, pharmacodynamics, Principle of Boundary layers, lubrication technology, short waves for heat-conducting fluids, sediment transportation, magnetohydrodynamics, multicomponent hydrodynamics, and electrohydrodynamic. Motivated by the development of biological fluid modeling and medical diagnosis instrumentation, this article examines the collective impacts of ion slip, viscous dissipation, Joule heating, and Hall current on unsteady generalized magnetohydrodynamic (MHD) Couette flow of two immiscible fluids. Two non-Newtonian incompressible magnetohydrodynamic micropolar and micropolar dusty (fluid-particle suspension) fluids are considered in a horizontal duct with heat transfer. No-slip boundary conditions are assumed at the channel walls and constant pressure gradient. Continuous shear stress and fluid velocity are considered across the interface between the two immiscible fluids. The coupled partial differential equations are formulated for fluids and particle phases and the velocities, temperatures, and microrotation profiles are obtained. Under the physically realistic boundary and interfacial conditions, the Modified cubic-Bspline differential quadrature approach (MCB-DQM) is deployed to obtain numerical results. The influence of the magnetic, thermal, and other pertinent parameters, i.e. Hartmann magnetic number, Eckert (dissipation) number, Reynolds number, Prandtl number, micropolar material parameters, Hall and ion-slip parameters, particle concentration parameter, viscosity ratio, density ratio, and time on velocity, microrotation, and temperature characteristics are illustrated through graphs. The MCB-DQM is found to be in good agreement with accuracy and the skin friction coefficient and Nusselt number are also explored. It is found that fluids and particle velocities are reduced with increasing Hartmann numbers whereas they are elevated with increment in ion-slip and Hall parameters. Temperatures are generally enhanced with increasing Eckert number and viscosity ratio. The simulations are relevant to nuclear heat transfer control, MHD energy generators, and electromagnetic multiphase systems in chemical engineering

Effect of Annealing on Magnetic and Structural Properties of FeNi Thin Films

In this work, we have deposited FeNi (60 nm) film on Si (111) substrate using electron beam evaporation technique. XRD measurements carried out on thin film with annealing the sample from 100 to 400 °C show increase in intensity of the FeNi (111) diffraction peak. The particle size increases from 19 nm (as deposited sample) to 27 nm (400 °C) with annealing. The magnetization measurements carried out using MOKE technique show enhancement in coercivity with annealing. The overall results are attributed in terms of annealing induced structural change which modify the magnetic properties

Study of Structural and Optical Properties of FeS2 Nanoparticles Prepared by Polyol Method

FeS2 nanoparticles were prepared using a simple and cost-effective Polyol method with ethylene glycol and precursor thiourea as capping reagents. The crystalline structure of FeS2 nanoparticles were confirmed by X-ray diffraction. Dimensions of the unit cell and Pa-3 space group were determined by Rietveld refinement. The average crystallite size was found to be ~ 42.1 nm. The stoichiometry of these nanoparticles were also confirmed by, Raman and Fourier Transform Infrared Spectroscopy. Further, Raman spectroscopy revealed the chemical bonding and symmetry of molecules. FTIR spectroscopy exhibited the presence of functional groups of Fe=S, Fe–S and S–S in the samples. Advanced measurements and analysis towards the applicability of surfactant coated pyrite FeS2 nanoparticles for solar cell etc. applications are in progress

Structural Investigation and Optical Properties of Silver Nanoparticles Synthesis by Chemical Method

We reported here the synthesis, structural characterization and optical properties of silver nanoparticles (Ag NPs). Chemical synthesis method was used to synthesize the Ag NPs. Ethylene was used as capping and reducing reagent. As prepared Ag NPs sample was characterized by X-ray diffraction, X-ray absorption spectroscopy (XAS), scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FTIR). Rietveld refinement of diffraction data revealed the dimensions of unit cell, hkl values, and Fm-3m space group of Ag NPs. The average crystallite size was found to be ~ 38.5 nm. Both X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) techniques at silver K-edge at BL-9 beam line at Indus-2 synchrotron radiation source (2.5 GeV, 125 mA), RRCAT, Indore (M. P.), India. A computer software package IFEFFIT was used to analyze physical parameters. FTIR revealed chemical bonding and symmetry of molecules

Root Cause Assessment for a Manufacturing Industry: A Case Study

Root-cause identification for quality related problems are key issues for manufacturing processes. It has been a very challenging engineering problem particularly in a multistage manufacturing, where maximum number of processes and activities are performed. However, it may also be implemented with ease in each and every individual set up and activities in any manufacturing process. Kaizen is aimed towards reduction in different types of losses i.e. Failure Loss/ Breakdown Loss, Minor stoppage, idling loss, Setup and adjustment loss etc. So as to improve quality and productivity.In this report, root-cause identification methodology has been adopted to eliminate the rejection of product manufactured by the enterprise and improving the life of product. Brainstorming and other Root Cause Assesmenttools have been used to find out the reasons of tube failure and vibration in tubular strander. Solutions of these problems have also given in this report. Kaizen activities have reduced the time consumed in daily activities of cleaning, lubricating, inspection etc. A detailed study has illustrated the effectiveness of the proposed methodology

Kinetics and mechanism of oxidation of [Mo(CN)₈]^4-[Mn(cdta)^- complex ion: Application of the Marcus relationship in support of an outer-sphere mechanism

857-862Oxidation of [Mo(CN)8]4-by [Mn(cdta)]-, studied as a function of disappearance of [Mn(cdta)]- at 510 nm, is a first order reaction with respect to both the ions. The linear plot between kobs and [H+] with intercept indicates two paths; one independent (k) of and the other (kH) dependent on [H+]. These paths are ascribed to the protonation equilibrium between [Mn(cdta)]- and H[Mn(cdta)],  by analogy to the similar equilibrium existing in [Mn(III)edta)]-complex, and is more likely than the equilibrium involving the protonation of [Mo(CN)84- ion. The alkali metal cations (M+) catalyze the observed rate in the order K+> Na+ > Li+ ion. The data provide linear correlations between kobs[Mo(CN)84-] and [M+], between kobs/[Mo(CN)84-] and polarisability of alkali metal cations beside a linear plot between kobs/[Mo(CN)84-] and  √m/(1+√m) with a predictable slope ~4 for the reaction between [Mn(cdta)]- and [Mo(CN)84-]. The first correlation, indicative of the ion-pair formation, is not favoured because the kobs value did not show sign of saturation. The second correlation indicates the formation of a bridge by the alkali metal ion between the oxidant and reductant species. The rate constants k and kH at 25° C are (7.32 ± 0.17)x103 dm6 mol-2 s-1 and (1.3 ± 0.02)X107 dm6 mol-2 s-1 respectively. The related values of the enthalpy and entropy are ΔHk#= 25 ± 2 kJ mol-1, ΔSk# = -70 ± 6 J K-1 mol-1, and ΔHkH# = 28 ± 2 kJ mol-1, & ΔSkH# = 2 ± 5 J K-1 mo-1 respectively. The use of the Marcus theory supports the outer-sphere nature of the reactio

Kinetics and mechanism of oxidation of oxovanadium(IV) by [Mn(cydta)]^- complex ion: Application of the Marcus relationship in support of an outer-sphere mechanism

952-959The rapid scan and the stopped-flow traces of the reaction mixture containing oxovanadium (IV) and [Mn(cydta)]- indicate the formation of intermediate complex(es). The inverse dependence of the rate on [H+] is attributed to the acidic dissociation of aquovanadium (IV) ion. Hence the intermediate complexes are formed between [VO(OH2)5]2+ and [VO(OH)(OH2)4]+ with [Mn(cydta)(OH2)]- and they decay in the rate limiting steps with rate constants kH2o and kOH respectively. The higher ratio of kOH/ kH2O 30 at 25°C , which previous workers considered to be indicative of an inner-sphere complex, perhaps, reflects the non-adiabaticity of the reaction with aquovanadium (IV) ion. The ratio is consistent with similar observations in several outer-sphere oxidations of VIV(aq) by metal complexes. The application of the Marcus relationship indicates that the reaction is better grouped with outer-sphere reactions of vanadium (IV) studied with well known outer-sphere oxidants. The values of the rate constants for the formation of the complex, and kH2O and kOH the respective rate constants for the decay of the [Mn(cydta)(OH2) ..VO(OH2)5]+ and [Mn(cydta)(OH2) ..VO(OH)(OH2)4] are reported