Charged Fluid Research Articles

On gel electrophoresis of dielectric charged particles with hydrophobic surface: A combined theoretical and numerical study.

A theoretical study on the gel electrophoresis of a charged particle incorporating the effects of dielectric polarization and surface hydrophobicity at the particle-liquid interface is made. A simplified model based on the weak applied field and low charge density assumption is also presented and compared with the full numerical model for a nonpolarizable particle to elucidate the nonlinear effects such as double layer polarization and relaxation as well as surface conduction. The main motivation of this study is to analyze the electrophoresis of the surface functionalized nanoparticle with tunable hydrophobicity or charged fluid drop in gel medium by considering the electrokinetic effects and hydrodynamic interactions between the particle and the gel medium. An effective medium approach, in which the transport in the electrolyte-saturated hydrogel medium is governed by the Brinkman equation, is adopted in the present analysis. The governing electrokinetic equations based on the conservation principles are solved numerically. The Navier-slip boundary condition along with the continuity condition of dielectric displacement are imposed on the surface of the hydrophobic polarizable particle. The impact of the slip length on the electrophoresis is profound for a thinner Debye layer, however, surface conduction effect also becomes significant for a hydrophobic particle. Impact of hydrophobicity and relaxation effects are higher for a larger particle. Dielectric polarization creates a reduction in its electrophoretic propulsion and has negligible impact at the thinner Debye length as well as lower gel screening length.

Application of Electrokinetic Stabilisation (EKS) Method for Soft Soil: A Review

Soil properties such as low shear strength, excessive compression, collapsing behavior, high swell potential are some of the undesirable properties of soils in geotechnical engineering and those properties would cause severe distress to the structures. To solve these, an innovative stabilization of Electrokinetic (EKS) has been introduced. Electrokinetic is an applicable technique to transport charged particles and fluid in an electric potential. The EKS demonstrates changes in soil pH due to electrolysis reactions, water flow between the electrodes and migration of ions towards the cathode. This treatment has proven its efficiency in consolidating organic, peat and clayey silt as well as less expensive than other methods. Otherwise, this method also gives advantage by not disturbing site. The primary objective of this review is to discuss the application of electrokinetic and to investigate the current knowledge of electrokinetic in geotechnical application through a literature search and review, including consideration of certain aspects related to the soft soil application that may be relevant to the future study and at the same time addressing some key issues and their implications on soil behaviors.

Viscoelastic pulsational mode

We present a theoretical model analysis to study the linear pulsational mode dynamics in viscoelastic complex self-gravitating infinitely extended clouds in the presence of active frictional coupling and dust-charge fluctuations. The complex cloud consists of uniformly distributed lighter hot mutually thermalized electrons and ions, and heavier cold dust grains amid partial ionization in a homogeneous, quasi-neutral, hydrostatic equilibrium configuration. A normal mode analysis over the closed set of slightly perturbed cloud governing equations is employed to obtain a generalized dispersion relation (septic) of unique analytic construct on the plasma parameters. Two extreme cases of physical interest depending on the perturbation scaling, hydrodynamic limits and kinetic limits are considered. It is shown that the grain mass and viscoelastic relaxation time associated with the charged dust fluid play stabilizing roles to the fluctuations in the hydrodynamic regime. In contrast, however in the kinetic regime, the stabilizing effects are introduced by the dust mass, dust equilibrium density and equilibrium ionic population distribution. Besides, the oscillatory and propagatory features are illustrated numerically and interpreted in detail. The results are in good agreement with the previously reported findings as special corollaries in like situations. Finally, a focalized indication to new implications and applications of the outcomes in the astronomical context is foregrounded.

Low-frequency shock waves in a magnetized superthermal dusty plasma

The characteristics of low-frequency shocks in a magnetized dusty plasma comprising of negatively charged dust fluid, kappa-distributed electrons and ions have been investigated. Using the reductive perturbation method, the nonlinear Korteweg de–Vries–Burgers (KdV–B) equation which governs the dynamics of the dust acoustic (DA) shock waves is derived. The characteristics of shock structures are studied under the influence of various plasma parameters, viz. superthermality of ions, magnetic field, electron-to-dust-density ratio, kinematic viscosity, ion-to-electron-temperature ratio and obliqueness. The combined effects of these physical parameters significantly influence the characteristics of DA shock structures. It is observed that only negative potential shocks exist in a plasma environment comprising of dust fluid and superthermal electrons and ions such as that of Saturn’s magnetosphere.

A hybrid, coupled approach for modeling charged fluids from the nano to the mesoscale

We develop and demonstrate a new, hybrid simulation approach for charged fluids, which combines the accuracy of the nonlocal, classical density functional theory (cDFT) with the efficiency of the Poisson–Nernst–Planck (PNP) equations. The approach is motivated by the fact that the more accurate description of the physics in the cDFT model is required only near the charged surfaces, while away from these regions the PNP equations provide an acceptable representation of the ionic system. We formulate the hybrid approach in two stages. The first stage defines a coupled hybrid model in which the PNP and cDFT equations act independently on two overlapping domains, subject to suitable interface coupling conditions. At the second stage we apply the principles of the alternating Schwarz method to the hybrid model by using the interface conditions to define the appropriate boundary conditions and volume constraints exchanged between the PNP and the cDFT subdomains. Numerical examples with two representative examples of ionic systems demonstrate the numerical properties of the method and its potential to reduce the computational cost of a full cDFT calculation, while retaining the accuracy of the latter near the charged surfaces.

Movement of CO2 Charged Fluids in Low Permeability Rocks During Deformation: Migration Patterns in the Carmel Formation, Utah

Understanding geodynamic reservoir and seal performance is important in order to ensure safe storage of CO2. In Utah leakage from natural gas reservoirs through sandstones and along faults may be observed as diagenetic alteration traces. Aeolian deposits, stained red by iron oxides, have commonly been bleached by reducing fluids of varying density. At the study site, bleaching is observed within and along the base of a low-permeability, regionally sealing unit; the lowermost Carmel Formation. Compactional stress during progressive deformation in the San Rafael monocline induced pressure gradients driving flow through the seal and towards venting fractures. Chemical transport processes are interpreted to be a combination of diffusion and advection. Capillary barriers may be overcome as transient in situ pressures and temperatures affecting fluid properties. The same geological unit may behave as a conduit during some parts of burial/uplift-history and as a sealing unit at other times.

Electroosmosis over charge-modulated surfaces with finite electrical double layer thicknesses: Asymptotic and numerical investigations

A theory of charge dynamics and fluid flow over charge-modulated surfaces is developed, finding nontrivial implications for finite thickness of an electrically charged interfacial layer. The results could be consequential in designing novel electrokinetic devices, including micromixers.

All spherically symmetric charged anisotropic solutions for compact stars

In the present paper we develop an algorithm for all spherically symmetric anisotropic charged fluid distributions. Considering a new source function nu (r) we find a set of solutions which is physically well behaved and represents compact stellar models. A detailed study specifically shows that the models actually correspond to strange stars in terms of their mass and radius. In this connection we investigate several physical properties like energy conditions, stability, mass–radius ratio, electric charge content, anisotropic nature and surface redshift through graphical plots and mathematical calculations. All the features from these studies are in excellent agreement with the already available evidence in theory as well as observations.

Beyond ideal magnetohydrodynamics: resistive, reactive and relativistic plasmas

We develop a new framework for the modelling of charged fluid dynamics in general relativity. The model, which builds on a recently developed variational multi-fluid framework for dissipative fluids, accounts for relevant effects like the inertia of both charge currents and heat and, for mature systems, the decoupling of superfluid components. We discuss how the model compares to standard relativistic magnetohydronamics and consider the connection between the fluid dynamics, the microphysics and the underlying equation of state. As illustrations of the formalism, we consider three distinct two-fluid models describing (i) an Ohm’s law for resistive charged flows, (ii) a relativistic heat equation, and (iii) an equation representing the momentum of a decoupled superfluid component. As a more complex example, we also formulate a three-fluid model which demonstrates the thermo-electric effect. The new framework allows us to model neutron stars (and related systems) at a hierarchy of increasingly complex levels, and should enable us to make progress on a range of exciting problems in astrophysics and cosmology.

Influence of interfacial viscosity on the dielectrophoresis of drops

The dielectrophoresis of a Newtonian uncharged drop in the presence of an axisymmetric nonuniform DC electric field is studied analytically. The present study is focused on the effects of interfacial viscosities on the dielectrophoretic motion and shape deformation of an isolated suspended drop. The interfacial viscosities generate surface-excess viscous stress which is modeled as a two-dimensional Newtonian fluid which obeys the Boussinesq-Scriven constitutive law with constant values of interfacial tension, interfacial shear, and dilatational viscosities. In the regime of small drop deformation, we have obtained analytical solution for the drop velocity and deformed shape by neglecting surface charge convection and fluid inertia. Our study demonstrates that the drop velocity is independent of the interfacial shear viscosity, while the interfacial dilatational viscosity strongly affects the drop velocity. The interfacial viscous effects always retard the dielectrophoretic motion of a perfectly conducting/dielectric drop. Notably, the interfacial viscous effects can retard or augment the dielectrophoretic motion of a leaky dielectric drop depending on the electrohydrodynamic properties. The shape deformation of a leaky dielectric drop is found to decrease (or increase) due to interfacial shear (or dilatational) viscosity.

Symmetry breaking bifurcations for an overdetermined boundary value problem on an exterior domain issued from electrodynamics

We consider an electrically charged fluid occupying a solid cylindrical region Ω of R3. Outside the domain Ω there is an electric field with electric potential which solves the Laplace equation and diverges as the distance from the axis tends to infinity. At ∂Ω the potential is constant and there is a balance between the pressure difference inside and outside the fluid, capillary forces proportional to the mean curvature and electrostatic repulsion of charges. We are interested in showing the existence of domains different from the solid cylinder Ω and satisfying the conditions described above. This problem is equivalent to an overdetermined elliptic boundary value problem on an exterior domain. We show the bifurcation phenomenon occurs and produces the deformation of the solid cylinder into rippled cylinders.

Thermodynamic behavior of charged Lennard-Jones fluids

In the present paper one of the simplest models for the intermolecular interaction of ionic substances is used. The phase equilibrium and pVT properties in the single-phase area for the fluid with intermolecular interaction, which is described by the Lennard-Jones and Coulomb potentials, is calculated by molecular dynamics simulation. Influence of the charge on position of the Zeno line as well as on a position of the vapor-liquid equilibrium line on phase diagram is determined. It is shown that this system can be described by generalized scaling laws proposed in a series of articles Apfelbaum E.M., Vorob'ev V.S.//J. Phys. Chem. B. 112. (2008) 13064. and Apfelbaum E.M., Vorob'ev V.S.//J. Chem. Phys. 130. (2009) 214111. The expression for the dependence of properties at the critical point, the Boyle temperature and density on the charge value are proposed.

Compressible fluids with Maxwell-type equations, the minimal coupling with electromagnetic field and the Stefan–Boltzmann law

In this work we have obtained a higher-derivative Lagrangian for a charged fluid coupled with the electromagnetic fluid and the Dirac’s constraints analysis was discussed. A set of first-class constraints fixed by noncovariant gauge condition were obtained. The path integral formalism was used to obtain the partition function for the corresponding higher-derivative Hamiltonian and the Faddeev–Popov ansatz was used to construct an effective Lagrangian. Through the partition function, a Stefan–Boltzmann type law was obtained.

Electromagnetic effects on the evolution of LTB geometry in modified gravity

We study the influence of Palatini $f(R)$ gravity and tilted observer on the dynamics of Lemaitre–Tolman–Bondi space-time in the presence of electromagnetic field. The imperfect charged fluid seen by tilted observer is considered in comparison with charged dust fluid seen by nontilted observer. We develop the relations between tilted and nontilted variables by including electric charge in Palatini $f(R)$ gravity. In this framework, we explore the evolution of energy density inhomogeneities for tilted and nontilted observers by calculating the energy conservation laws for charged fluid. Finally, we evaluate a constraint on the electric charge in the collapse of stellar objects, which leads to the instability of nontilted congruence.

Interaction and propagation characteristics of two counter and co-propagating Mach cones in a dusty plasma

We theoretically investigate the interaction and propagation characteristics of two co/counter propagating Mach cones triggered by two projectile particles moving with supersonic velocities in the same/opposite directions through a dusty plasma medium. The Mach cone solutions are obtained by solving a model set of fluid equations for a heavily charged dust fluid that includes the contributions of the projectile particles in the Poisson equation. The density profiles and velocity vector maps of the Mach wings show interesting structural changes when they interact with each other and form patterns similar to interference fringes. Compared to the co-propagating Mach cones, the wings of counter propagating Mach cones produce a larger number of maxima and minima in the pattern resulting from their mutual interaction. In addition, the time duration of the formation of two maxima or minima at a particular point decreases due to the interactions of Mach cones. Another notable feature is that the spacing between adjacent maxima increases, while the fringe angle decreases with the increase of relative velocity of the counter propagating projectile particles.

Relativistic Heat Flux for a Single Component Charged Fluid in the Presence of an Electromagnetic Field

AbstractTransport properties in gases are significantly affected by temperature. In previous works it has been shown that when the thermal agitation in a gas is sufficient for relativistic effects to become relevant, heat dissipation is driven not solely by a temperature gradient but also by other vector forces. In the case of relativistic charged fluids, a heat flux is driven by an electrostatic field

Thermoelectric and Thermomagnetic Effects in Kaluza’s Kinetic Theory

AbstractA five-dimensional treatment of the Boltzmann equation is used to establish the constitutive equations that relate thermodynamic fluxes and forces up to first order in the gradients for simple charged fluids in the presence of electromagnetic fields. The formalism uses the

Application of kinetic flux vector splitting scheme for solving multi-dimensional hydrodynamical models of semiconductor devices

In this article, one and two-dimensional hydrodynamical models of semiconductor devices are numerically investigated. The models treat the propagation of electrons in a semiconductor device as the flow of a charged compressible fluid. It plays an important role in predicting the behavior of electron flow in semiconductor devices. Mathematically, the governing equations form a convection–diffusion type system with a right hand side describing the relaxation effects and interaction with a self consistent electric field. The proposed numerical scheme is a splitting scheme based on the kinetic flux-vector splitting (KFVS) method for the hyperbolic step, and a semi-implicit Runge–Kutta method for the relaxation step. The KFVS method is based on the direct splitting of macroscopic flux functions of the system on the cell interfaces. The second order accuracy of the scheme is achieved by using MUSCL-type initial reconstruction and Runge–Kutta time stepping method. Several case studies are considered. For validation, the results of current scheme are compared with those obtained from the splitting scheme based on the NT central scheme. The effects of various parameters such as low field mobility, device length, lattice temperature and voltage are analyzed. The accuracy, efficiency and simplicity of the proposed KFVS scheme validates its generic applicability to the given model equations. A two dimensional simulation is also performed by KFVS method for a MESFET device, producing results in good agreement with those obtained by NT-central scheme.

A New Charged Anisotropic Compact Star Model in General Relativity

In the present article, we explore a new static, spherically symmetric charged anisotropic fluid model of compact star in curvature coordinates. We consider metric potential g44 of Durgapal’s fifth solution [1] with a specific choice of electric field intensity E and physically acceptable expression of anisotropy factor Δ , which involve parameters K (charge) and Δ (anisotropy) respectively. The solution so obtained is utilized to construct the model for superdense star like neutron star. We have analysed that corresponding to X=0.1, K=2.8, a=1.6 and by assuming surface density , the mass of the compact star comes out to be with radius 14.51 kms, which closely resembles to that of PSRJ0348 + 0432. The solution is well behaved for the values of K satisfying 1≤K5. Our model is described analytically as well as with the help of graphical representations. Our solution is well behaved and free from any central singularity. It also satisfies all the energy conditions as well as the causality condition thus reconfirming the stability of our model.

New Class of Heintzmann Exact Solution in General Relativity for an Isotropic Charged Stellar Model

Exact solution for spherically symmetric isotropic charged fluid sphere are investigated relativistic model of an electrically charged compact star, and energy density associated with the electric fluids is on the same order of magnitude as the energy density of fluid matter itself. The analytic solution depicts a unique static charged configuration of quark matter with radius R~9 km and total mass M~2.5M⊙. And try to inspect the velocity of sound approximately 1/√3 which is similar to the attitude of SQM (Strange Quark matter). Adiabatic index conform the stability of star if the adiabatic index is less than 4/3. Based on an analytic model in the recent work, the applicable values of physical quantities have been calculated by accepting the estimated masses and radii of some well-known strange star candidates like PSR J1903+327, Her X-1, Cen X-3, EXO 1785-248.