Viscous Liquid Medium Research Articles

Behavior of magnetic systems of different dimensions in a magnetic field

Purpose. To investigate the influence of the magnetic field on the formation of structures in magnetic media of various dispersities. Methods. Experiments to study the dynamics of magnetic inclusions were carried out on a self-made installation in flat transparent cells by microscopy. The magnetic field was created by an electromagnet FL-1 connected to a power source. Magnetite particles of various sizes, as well as metal balls with a diameter of 0.5 mm, were studied as a magnetic medium. Video recording was performed using a MICMED WiFi 2000X 5.0 microscope. Results. The dynamics of magnetic inclusions in a viscous liquid medium under the influence of a magnetic field, as well as under conditions of mechanical shear effects, have been studied. The influence of the magnetic field strength on the growth rate of chain structures, as well as on the angle of deflection under shear action, has been studied. A theoretical interpretation of the observed phenomena is proposed. Conclusion. During the experiment, it was found that under the influence of a magnetic field, magnetic inclusions form chain structures. Their size, growth rate and dynamics depend on the physical parameters of the system and the external magnetic field. An intensive increase in the formation of chains of magnetic inclusions was detected at low and medium values of the magnetic field strength. An experimental dependence of the angle of deviation of chain structures from the equilibrium position on the magnetic field strength is obtained, which correlates with known theoretical data, on the basis of which a computational model is proposed. The results of the study can be used to visualize numerical calculations of the dynamics of dispersed systems under external influences.

Another Piece of the Ionic Liquid's Puzzle: Adsorption of Cl- Ions.

Classical electrochemical and microscopy methods were used to characterize the interfacial processes of the adsorption of chloride ions from ionic liquids at the Bi(111) single crystal electrode. The mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium chloride was electrochemically characterized by using cyclic voltammetry and electrochemical impedance spectroscopy. In situ scanning tunneling microscopy images showed the formation of superstructures at the electrode's surface over an extended period of time. The specific adsorption of chloride ions reaches an equilibrium state in a more viscous ionic liquid medium slower than in aqueous and organic solvents. Capacitance values increase considerably (also depending on alternative current frequency) at the potential region, where the specific adsorption of chloride ions with partial charge transfer occurs.

An Analysis and Global Identification of Smoothless Variable Order of a Fractional Stochastic Differential Equation

We establish both the uniqueness and the existence of the solutions to a hidden-memory variable-order fractional stochastic partial differential equation, which models, e.g., the stochastic motion of a Brownian particle within a viscous liquid medium varied with fractal dimensions. We also investigate the inverse problem concerning the observations of the solutions, which eliminates the analytic assumptions on the variable orders in the literature of this topic and theoretically guarantees the reliability of the determination and experimental inference.

Hydrodynamic Model and Kinetics of Dispersion of a Solid Disperse Phase in the Process of Mixing in a Viscous Liquid Medium

Hydrodynamic Model and Kinetics of Dispersion of a Solid Disperse Phase in the Process of Mixing in a Viscous Liquid Medium

Behavior of Gas Entrainment Inside Viscous Pool Due to Combined Influence of Symmetric Rotational Field and Freestream Flow of Air

Abstract The present investigation elucidates the interfacial characterization caused by the simultaneous effect of a symmetric converging rotational field and continuous air stream flow above the free surface. The converging rotational field is developed by a couple of counter and equal rotating rollers fully immersed inside the viscous liquid medium and their centers are aligned along a horizontal line. Such phenomenon is abundantly encountered in various engineering devices, where the interactions and transfer of mass, momentum, and energy are quite important through gas–liquid interfaces. Behavior of entrainment profile is observed due to the influence of various relevant pertinent parameters, namely, rotational of speed (measured by Ca), submersion depth (b*), the gap between the rollers (2a*), and strength of air stream flow (measured by Reflow). An upper rounded structured interfacial configuration is obtained for all cases of Ca when the rollers are located very close to each other. The length of the entrainment of cusp decreases with the rise of Reflow for the same value of Ca. The value of Cac increases continuously with the increase of Reflow for a particular of 2a* and b*. Bubble ejection from filament tip and subsequent accumulation increases significantly with the rise of Ca for a particular case of Reflow. The cusp tip progressively traverses in upward direction with the continuous increase of gravitational pull for a particular value of Ca and Reflow. Entrainment length progressively grows with the continuous rise of viscous drag for a particular value of Ca and Reflow. Finally, an analytical formulation is proposed to analyze the structure of entrainment and this model reports an excellent match with the numerical findings.

Frequency shift prediction of a shear mode multi-layered FBAR sensor in viscous media using transfer matrix method

In this paper, new frequency equations of a shear mode c-axis tilted FBAR (Film Bulk Acoustic Wave Resonator) sensor operating in viscous liquid media are derived by using the transfer matrix method to predict the frequency shift (FS) induced by fluid viscosity. Top and bottom electrodes of FBAR are considered as a superposition of a pure elastic model and a perfectly conducting model. Employing the perturbation method and developed frequency equations, an approximate FS expression is obtained to study the effects of viscous liquid properties on frequency shifts for the sensor operating in water-glycerol solutions. Numerical results by the developed frequency equations are compared with the published experimental results and those predicted by the traditional Stockbridge-Kanazawa equation, which was originally derived for quartz crystal microbalances (QCMs). Meanwhile, the influence of the electrode material and thickness on FS is also discussed to demonstrate the outperformance of the developed equations over the Stockbridge-Kanazawa equation. Results show that the analytical equations for frequency shift analysis have more potential than the well-known Stockbridge-Kanazawa equation to predict frequency shift characteristics of FBAR sensors in terms of accuracy and efficiency.

Non-Newtonian coefficient condition for a stable long-time behavior of a single bubble: existence and characteristics of stable solutions

The present paper takes up the underlying nonlinear initial value problem from a preceding author’s work about the dynamics of a single bubble in a highly viscous liquid medium under different pressure impacts. The arising ordinary differential equation is mainly based on the constitutive relation of a second-order liquid that in particular includes two non-Newtonian material constants. In this article, the significance of these coefficients is mathematically analyzed in detail by proving the existence of stable solutions of the named initial value problem. This is achieved by special transformations of the differential equation at hand and the introduction of appropriate Lyapunov functions. It particularly turns out that a combined condition of the non-Newtonian coefficients and diverse restrictions to the external pressure impact are decisive for the validity of the existence results. Furthermore, the convergence speed of solutions is investigated by considering the linearized equation associated with the present initial value problem and by applying a special variant of Gronwall’s lemma. The main theoretical result, being the prementioned strong condition for the non-Newtonian coefficients, is finally compared to real data sets.

In situ solid-state NMR of a magnetically oriented microcrystal suspension.

In situ solid-state NMR measurements of a magnetically oriented microcrystal suspension (MOMS) were demonstrated. Under modulated rotation of the static field, or equivalently, of the sample tube, randomly oriented microcrystals in a viscous liquid medium feel a torque arising from the anisotropic bulk susceptibility and eventually aligned in the same direction. In this way, a three-dimensional MOMS (3D-MOMS) was obtained. To apply an elliptically rotating magnetic field to microcrystals in suspension, a probe to rotate the sample tube around an axis perpendicular to the static magnetic field was developed. Single-crystal (SC) rotation patterns were obtained from the 3D-MOMS by solid-state CP measurements triggered in synchronous with the sample-tube rotation. Unlike the traditional SC method, the 3D-MOMS approach presented here does not require the elaborate adjustment of the direction of the reference frame. The process of three-dimensional magnetic alignment was also studied by monitoring the spectral changes during continuous application of the modulated sample rotation.

Understanding of Fluidic Physics during Bypass of a Taylor Bubble around a Transverse Insert in a Viscous Medium

Fluidic physics during bypass of a Taylor bubble around a transverse insert is experimentally observed in a viscous liquid medium. Unified and fragmented bypasses are identified depending on the length scale of the insert. Sequential stages of these mechanisms are elaborated on from the kinematics of the bubble. Prediction of the bypass and pinch-off time scale validates the required diameter ratio between the insert and tube for a transition. Using photographic analysis, phenomena like air-jet plunging, neck recovery, and shape transformation of daughter bubbles are discussed for the bypass and pinch-off systems. The 2D collapse of the gas stem at the initial stage and the volumetric pinch-off in the later stages have been conceptualized. The stability of the bubble train in pinch-off systems is evaluated, and coalescing/noncoalescing trains are identified by predicting the wake length. A pressure-jump model has been proposed to identify the reason for bubble-unified bypass and pinch-off.

Slot coating flow of particle suspensions: Particle migration in shear sensitive liquids

The functionality of several coated products, such as anti-reflection films and flexible electronics, depends on the complex microstructure of the deposited liquid layer. In many of these applications, the coating liquid is a particle suspension composed by small, solid particles suspended in a viscous liquid medium. Particle suspensions are classified as non-Newtonian fluids, especially at high concentrations. The non-Newtonian behavior of the coating liquid strongly affects the inner structure of the deposited liquid layer and the operability limits of slot coating processes. In this work, we study particle migration and the low-flow limit in slot coating flows of particle suspensions. Both shear rate sensitive and non shear rate sensitive suspensions are considered, and shear-induced particle migration is described by the Diffusive Flux Model. The conservation equations are solved together with the elliptic mesh-generation method to compute the position of the free surfaces using a stabilized Finite Element Method. The results show how particle migration and the rheology of the coating liquid affect the final particle distribution on the deposited liquid film and the process limits in a typical slot coating flow.

Surface wave propagation in functionally graded piezoelectric material: An analytical solution

Wentzel–Kramers–Brillouin approximation technique serves as a powerful tool to find the particle displacements due to surface wave propagation in bedded structure with distinct material properties. This study is carried out to investigate the transference of Love-type waves in functionally graded piezoelectric material layer bonded between viscous liquid and pre-stressed piezoelectric half-space. Following the elastic wave theory, the mathematical model is established. Wentzel–Kramers–Brillouin method is applied to obtain the theoretical derivations in functionally graded piezoelectric material stratum where variation in material gradients is taken exponentially. Separation of variables method is employed to obtain the displacement components in viscous liquid and piezoelectric medium. Dispersion equations for considered surface wave are obtained in both electrically open and short cases. Profound effect of material gradient coefficient on phase velocity has been remarkably established. Some numerical examples are carried out and represented through graphs. The considered model facilitates a theoretical foundation and practical application for the development of surface acoustic wave devices.

A Theoretical Study of Love Wave Sensors Based on ZnO-Glass Layered Structures for Application to Liquid Environments.

The propagation of surface acoustic Love modes along ZnO/glass-based structures was modeled and analysed with the goal of designing a sensor able to detect changes in the environmental parameters, such as liquid viscosity changes and minute amounts of mass supported in the viscous liquid medium. Love mode propagation was modeled by numerically solving the system of coupled electro-mechanical field equations and Navier–Stokes equations. The phase and group velocities and the attenuation of the acoustic wave propagating along the 30° tilted c-axis ZnO/glass structure contacting a viscous non-conductive liquid were calculated for different ZnO guiding layer thicknesses, added mass thicknesses, and liquid viscosity and density. The three sensor responses, i.e., the wave phase and group velocity, and attenuation changes are calculated for different environmental parameters and related to the sensor velocity and attenuation sensitivities. The resulted sensitivities to liquid viscosity and added mass were optimized by adjusting the ZnO guiding layer thickness corresponding to a sensitivity peak. The present analysis is valuable for the manufacture and application of the ZnO-glass structure Love wave sensors for the detection of liquid properties, such as viscosity, density and mass anchored to the sensor surface.

점성유체 액/고 순환유동층에서 입자의 순환속도

Characteristics of solid circulation rate in the liquid-solid circulating fluidized beds with viscous liquid medium were investigated. Effects of primary and secondary liquid velocities, particle size, liquid viscosity and height of solid particles piled up in the solid recycle device on the solid circulation rate were considered. The solid circulation rate increased with increasing primary and secondary liquid velocities, liquid viscosity and height of solid particles in the downcommer, but it decreased with increasing particle size. The particle rising velocity in the riser decreased with increasing the ratio of UL1/UL2 and particle size. The slip velocity of liquid and particle, UL/US, decreased with increas- ing liquid viscosity but it increased with increasing particle size. The values of solid circulation rate were well cor- related in terms of operating variables and dimensionless groups.

Modeling the fluid dynamics and heat transfer in unsteady and periodic flow of a highly concentrated granular medium over an obstacle in a channel

The unsteady isothermal flow of a dense layer of a granular medium around an obstacle in a plane channel is modeled using the momentum transfer equations for an incompressible viscous liquid medium based on the slip of the medium at the walls. The validity of this approach is tested by comparing the calculated and experimental data for the flow of a highly concentrated granular medium with high flowability. The effect of periodic change in the flow rate of the granular medium over time in the inlet section of the plane channel on the unsteady distributions of the velocity and temperature fields is studied.

Study on Liquid QCM Sensor Design and its Response Model

We use quartz crystal material from a physical point of constitutive equations derived in detail combined with the boundary conditions of the liquid Kanasawa QCM response model and Martin correction BVD equivalent circuit model; then apply transmission line theory and the theory of Acoustic impedance load, the research results can be useful as a QCM-D model, response model and Martin mode, then in-depth analysis of the liquid phase conditions, factors affecting the QCM frequency change, we propose a new method for measuring the density of the unknown liquid viscosity supplement. The main purpose of this chapter is to illustrate the viscous liquid medium under contact conditions, based on transmission line theory and the theory of load Acoustic impedance method compared to the classical method is simple, accurate, and effective.

Size dependence study on magnetic heating properties of superparamagnetic iron oxide nanoparticles suspension

We studied the magnetic heating properties of nearly monodispersed iron oxide nanoparticles (NPs) suspended in liquid media. Iron oxide NPs with a narrow size distribution (σ ∼ 0.1) with various median diameters were synthesized by the seed-mediated growth method. The effect of size on specific absorption rate (SAR) was investigated for median diameters ranging from 9 to 15 nm at intervals of 1 nm. The maximum value of SAR was found at about 13 nm for the samples dispersed in a viscous liquid media. Calculated SAR using linear response theory explains the results qualitatively but showed quantitative disagreement. This discrepancy was explained by assuming the existence of a magnetically frustrated layer on the seed NPs.

Solid holdup in liquid solid circulating fluidized bed with viscous liquid medium

Average solid holdup in the axial direction was investigated in a liquid solid circulating fluidized bed riser (LSCFB), with liquids of different viscosities. The effect of operating parameters including; primary, secondary and total velocity, particle diameter and density was studied. Experiments were conducted using water and glycerol at different concentration having viscosities in the range 1–1.36cp. The results indicated that the solid holdup in the riser was axially uniform for viscous liquids and increases with increase in auxiliary velocity. The average solid holdup decreases with increase in total velocity and increases with increase in viscosity for sand–glycerol, glass bead–glycerol system. The experimental measurements were compared with the existing holdup model prediction that varied linearly with viscosity. Further, a correlation was developed to estimate average solid holdup in the riser, and the performance of the expression was compared with the present experimental data.

Effect of hydrodynamic force on microcantilever vibrations: Applications to liquid-phase chemical sensing

At the microscale, cantilever vibrations depend not only on the microstructure's properties and geometry but also on the properties of the surrounding medium. In fact, when a microcantilever vibrates in a fluid, the fluid offers resistance to the motion of the beam. The study of the influence of the hydrodynamic force on the microcantilever's vibrational spectrum can be used to either (1) optimize the use of microcantilevers for chemical detection in liquid media or (2) extract the mechanical properties of the fluid. The classical method for application (1) in gas is to operate the microcantilever in the dynamic transverse bending mode for chemical detection. However, the performance of microcantilevers excited in this standard out-of-plane dynamic mode drastically decreases in viscous liquid media. When immersed in liquids, in order to limit the decrease of both the resonant frequency and the quality factor, and improve sensitivity in sensing applications, alternative vibration modes that primarily shear the fluid (rather than involving motion normal to the fluid/beam interface) have been studied and tested: these include in-plane vibration modes (lateral bending mode and elongation mode). For application (2), the classical method to measure the rheological properties of fluids is to use a rheometer. However, such systems require sampling (no in situ measurements) and a relatively large sample volume (a few milliliters). Moreover, the frequency range is limited to low frequencies (less than 200Hz). To overcome the limitations of this classical method, an alternative method based on the use of silicon microcantilevers is presented. The method, which is based on the use of analytical equations for the hydrodynamic force, permits the measurement of the complex shear modulus of viscoelastic fluids over a wide frequency range.

Investigation of motility and biofilm formation by intestinal Campylobacter concisus strains

Motility helps many pathogens swim through the highly viscous intestinal mucus. Given the differing outcomes of Campylobacter concisus infection, the motility of eight C. concisus strains isolated from patients with Crohn’s disease (n=3), acute (n=3) and chronic (n=1) gastroenteritis and a healthy control (n=1) were compared. Following growth on solid or liquid media the eight strains formed two groups; however, the type of growth medium did not affect motility. In contrast, following growth in viscous liquid medium seven of the eight strains demonstrated significantly decreased motility. In media of increasing viscosities the motility of C. concisus UNSWCD had two marked increases at viscosities of 20.0 and 74.7 centipoises. Determination of the ability of UNSWCD to swim through a viscous medium, adhere to and invade intestinal epithelial cells showed that while adherence levels significantly decreased with increasing viscosity, invasion levels did not significantly change. In contrast, adherence to and invasion of UNSWCD to mucus-producing intestinal cells increased upon accumulation of mucus, as did bacterial aggregation. Given this aggregation, we determined the ability of the eight C. concisus strains to form biofilms, and showed that all strains formed biofilms. In conclusion, the finding that C. concisus strains could be differentiated into two groups based on their motility may suggest that strains with high motility have an increased ability to swim through the intestinal mucus and reach the epithelial layer.

Particle dispersion and fluctuations in viscous liquid–solid fluidised Beds

AbstractParticle dispersion and fluctuations were investigated in a liquid–solid fluidised bed with viscous liquid media by employing the relaxation method based on the stochastic model. The bed expansion or contraction during the transient state was analysed by means of the histogram of pressure drop variation with elapsed time. The relaxation behaviour of the liquid–solid fluidised bed appeared to be heterogeneous followed by homogeneous expansion or contraction. Effects of liquid velocity (UL), particle size (dP), liquid viscosity (µL) and liquid holdup or bed porosity (εL) on the fluctuating frequency (F) and dispersion coefficient (DP) of fluidised solid particles were examined. The values of F and DP increased with an increase in dP but decreased with µL and exhibited local maxima with variations of UL and εL. The flow pattern of solid particles could be changed from uniform or pseudo‐homogeneous to turbulent random behaviour with an increase in the liquid velocity and liquid holdup or bed porosity. © 2012 Canadian Society for Chemical Engineering