Charged Fluid Research Articles

Collective Effects in Ionic Liquid [emim][Tf2N] and Ionic Paramagnetic Nitrate Solutions without Long-Range Structuring.

Mesoscopic shear elasticity has been revealed in ordinary liquids both experimentally by reinforcing the liquid/surface interfacial energy and theoretically by nonextensive models. The elastic effects are here examined in the frame of small molecules with strong electrostatic interactions such as room temperature ionic liquids [emim][Tf2N] and nitrate solutions exhibiting paramagnetic properties. We first show that these charged fluids also exhibit a nonzero low-frequency shear elasticity at the submillimeter scale, highlighting their resistance to shear stress. A neutron scattering study completes the dynamic mechanical analysis of the paramagnetic nitrate solution, evidencing that the magnetic properties do not induce the formation of a structure in the solution. We conclude that the elastic correlations contained in liquids usually considered as viscous away from any phase transition contribute in an effective way to collective effects under external stress whether mechanical or magnetic fields.

Charged anisotropic fluid spheres with conformal symmetry

Charged anisotropic fluid spheres with conformal symmetry

Effect of electric field on string-oriented perfect fluid collapse in f (R) gravity

This work investigates the nature of singularity formed from string-oriented charged perfect fluid collapse in theory of f (R) gravity. The spherically symmetric spacetime is assumed to be filled with a string-oriented charged perfect fluid. The gravitational collapse of the fluid is analyzed to understand the effects of electric field on the time and radii of apparent horizons and singularity formation. The presence of an electric field was discovered to increase the mass of the collapsing system, the radii of apparent horizon development, and the time gap between the event horizon and singularity. The term [Formula: see text] acts as an anti-gravity term. However, the presence of electric field accelerates the gravitational collapse.

Simulations of phase transitions and capacitance, of simple ionic fluids in porous electrodes

In this work, we simulate the capacitance of a simple charged fluid model consisting of equal-sized, spherical monovalent ions, immersed in an implicit solvent. Apart from Coulomb forces, the particles interact via a truncated and shifted Lennard-Jones potential. This is a possible crude model for hydrophobic ions (assuming an implicit aqueous solvent) and allows for a possible demixing transition in the solution. Such a phase separation may be driven by charging a narrow slit-like pore, immersed in a dilute (“gas-like”) bulk phase, akin to a capillary condensation. We highlight the dramatic effect that boundary conditions and regulatory control have on electrical properties (e.g., the differential capacitance) at the point of transition. For example, the surface potential displays a vertical (first-order) transition, as a function of surface charge density, when the latter is constrained to be uniform over the pore surfaces. At short separations, the transition is gradual (i.e., not first-order), which leads to a regime with an apparent ”non-physical” negative differential capacitance. Under conditions of constant surface potential, the negative capacitance region becomes inaccessible, as a first-order (horizontal) transition is reasserted. This is true for both conducting and non-conducting surfaces.

Stochastic Variational Principles for Dissipative Equations with Advected Quantities

This paper presents symmetry reduction for material stochastic Lagrangian systems with advected quantities whose configuration space is a Lie group. Such variational principles yield deterministic as well as stochastic constrained variational principles for dissipative equations of motion in spatial representation. The general theory is presented for the finite-dimensional situation. In infinite dimensions we obtain partial differential equations and stochastic partial differential equations. When the Lie group is, for example, a diffeomorphism group, the general result is not directly applicable but the setup and method suggest rigorous proofs valid in infinite dimensions which lead to similar results. We apply this technique to the compressible Navier–Stokes equation and to magnetohydrodynamics for charged viscous compressible fluids. A stochastic Kelvin–Noether theorem is presented. We derive, among others, the classical deterministic dissipative equations from purely variational and stochastic principles, without any appeal to thermodynamics.

Hydrodynamic simulation studies on avalanche and streamer formation in GEM detector

The dynamics of electrons and ions in gaseous ionization detectors have been studied reasonably well with particle simulation models developed using the Garfield++ numerical simulation framework. This is an important area of study since it allows prediction of the detector response in a given experimental situation. In this work, a fluid simulation model has been developed in the COMSOL Multiphysics simulation framework to simulate the avalanche and streamer formation in GEM-based detectors. Possible detector geometries in 2D, 2D axisymmetric and 3D coordinate systems have been explored to find the optimum numerical configuration. Transport of charged fluids has been simulated in the optimized model for various operating voltage ranges suitable for single, double and triple GEM detectors using Ar-CO2 (70-30) as the gas mixture. Simulated gain variations have been compared with experimental observations. Effect of space charge and its relation to streamer formation have been studied.

Working fluid study for loop heat pipes

Loop heat pipes (LHPs) provide unique applications for high heat flux and long distance heat transfer. Working fluid aspects, including liquid charging ratio, type and fluid dynamics, in loop heat pipe is quite different as compared to conventional heat pipe. This paper will particularly endeavor to explain these differences, and provide optimal design conditions achieved via experimental study. Design considerations and operational aspects of LHP with respect to working fluid is evaluation and discussed in detail. Important thermal-fluid properties with respect to pressure-temperature relation and merit number are outlined for various heat transfer fluids to choose best option for given conditions. LHP with capillary evaporator, 25 mm diameter and 155 mm long, and heat transfer length ∼250 mm was designed to study and optimize different working fluid aspects including optimum working fluid range for different orientations, effect of fluid type on performance and operational dynamics of loop related to fluid (start-up, oscillations, hysteresis and buoyancy effects). Loop utilized copper containment, nickel wick and mainly water as working fluid. As an outcomes of this investigation, it has been concluded that liquid ratio in range of 40 to 60 % of loop volume provide optimum charge, for different orientations, with 50 % charge showing best thermal performance. In summary, considered working fluid type and optimized overall liquid amount, calculated by giving due consideration to volumes of different loop components, can help to get best performance from the loop systems.

The role of the electric Bond number in the stability of pasta phases

The deformation of nuclei in the neutrons star crust can be modelled by the system of two charged fluids separated by the phase boundary with non-zero surface tension. The stability of highly elongated structures, called pasta phases, is discussed here. In this work the cylindrical and spherical portion of charged fluids are considered. Their behavior depends on whether they are in vacuum or in charged surroundings what is modelled by Wigner-Seitz cell. The electric Bond number appears to be crucial parameter in the analysis. Variety of different unstable modes in vacuum case is strongly reduced in the case of W-S cell. It comes from the virial theorem, which bounds the value of the Bond number and reduces the role played by electric forces. Although the analysis is motivated by the nuclear pasta phases it can be applied to any system of two charged fluids.

Quantum simulations of hydrodynamics via the Madelung transformation

Developing numerical methods to simulate efficiently nonlinear fluid dynamics on universal quantum computers is a challenging problem. In this paper, a generalization of the Madelung transform is defined to solve quantum relativistic charged fluid equations interacting with external electromagnetic forces via the Dirac equation. The Dirac equation is discretized into discrete-time quantum walks which can be efficiently implemented on universal quantum computers. A variant of this algorithm is proposed to implement simulations using current noisy intermediate scale quantum (NISQ) devices in the case of homogeneous external forces. High resolution (up to $N={2}^{17}$ grid points) numerical simulations of relativistic and nonrelativistic hydrodynamical shocks on current IBM NISQs are performed with this algorithm. This paper demonstrates that fluid dynamics can be simulated on NISQs, and opens the door to simulating other fluids, including plasmas, with more general quantum walks and quantum automata.

Coherent radiation of photons by particle wave packets

The radiation of photons by electrons is investigated in the framework of quantum electrodynamics up to the second order in the coupling constant e. The N-particle, coherent, and thermal initial states are considered and the forms of the electron wave packets are taken into account. The explicit expressions for the intensity of radiation and the inclusive probability to record a photon are obtained. It is found that there are three processes in this order of perturbation theory where the electron wave packet radiates coherently and can be regarded as a charged fluid even on integrating over the final states of the electron, i.e., in considering the inclusive probabilities and intensity of radiation. These processes are stimulated radiation by an electron, coherent radiation from a beam of particles, and reradiation of a photon in the Compton process. We obtain the explicit expressions for the intensity of radiation and the inclusive probability to record a photon for these processes. As particular cases, we consider: stimulated transition radiation produced by an electron wave packet traversing a mirror and backlighted by a laser wave, reradiation of photons in a coherent state by an electron wave packet. In the latter case, we deduce that the wave packet of a single electron can be endowed with the susceptibility tensor and this tensor has the same form as for an electron plasma in the small recoil limit.

Dissipative charged homologous model for cluster of stars in f(R,T) gravity

In this paper, we discuss homologous model for cluster of stars in f ( R , T ) gravity. For this purpose, we use f ( R , T ) = R + K ( − T ) n model to incorporate exotic terms in the system. The quasi-static approximations are being imposed onto the shear-free dissipative relativistic self-gravitating charged fluid. It is found that non-dissipative case can easily be reduced to linear homology law in the Newtonian regime. In dissipative scenario, this condition exhibits that the linear homology law for a fluid element is applicable only if we apply the homology conditions on temperature, emission rate and charge associated to baryonic matter. For dark matter, it depends upon the emission of gravitational dissipation. We also deduce that the shear-free and homogeneous expansion rate conditions are equivalent to the homology conditions only in the Newtonian limit. Furthermore, the deviation from homology conditions leads to thermal peeling effects. We use PSR J 1614 − 2230 data with f ( R , T ) field equations for which the graphical analysis shows that the physical variables of baryonic matter like density, pressures and dissipation are suppressed in the presence of dark matter. Thus dark matter has a significant relevance in the emergence of homologous evolution of stellar cluster.

Thermal stability with emission energy and Joule–Thomson expansion of regular BTZ-like black hole

We investigate the thermodynamic properties and Joule–Thomson expansion for conical or BTZ-like black holes. To analyze the thermal stability, we discuss the temperature and thermal stability relative to the horizon radius for different values of model parameters beta _0 and alpha _2. Moreover, we analyze thermodynamical geometries like Ruppeiner, Weinhold and Hendi Panahiyah Eslam Momennia formulation and calculate respective scalar curvatures for BTZ-like black holes. Interestingly, the black holes have no singularity in some cases, i.e., completely regular. We obtain the inversion temperatures and inversion curves and investigate the similarities and differences between van der Waals and charged fluids. To discuss this expansion, we use a BTZ-like black hole. Further, we establish the position of the inversion point versus different values of mass mu , and the parameters beta _0 and alpha _2 for such a BTZ-like black hole. The Joule–Thomson coefficient mu at this point disappears. A crucial trait upon which we relied to inspect the sign of quantity mu to get the cooling-heating areas. We also investigate the energy emission depending upon the frequency omega .

Charged quark stars in f(R,T) gravity* *JMZP acknowledges financial support from the PCI program of the Brazilian agency "Conselho Nacional de Desenvolvimento Científico e Tecnológico"–CNPq. T. Tangphati was supported by King Mongkut's University of Technology Thonburi's Post-doctoral Fellowship. A. Pradhan thanks IUCCA, Pune, India for providing facilities under associateship programmes

Recent advances in nuclear theory and new astrophysical observations have led to the need for specific theoretical models applicable to dense-matter physics phenomena. Quantum chromodynamics (QCD) predicts the existence of non-nucleonic degrees of freedom at high densities in neutron-star matter, such as quark matter. Within a confining quark matter model, which consists of homogeneous, neutral 3-flavor interacting quark matter with corrections, we examine the structure of compact stars composed of a charged perfect fluid in the context of gravity. The system of differential equations describing the structure of charged compact stars has been derived and numerically solved for a gravity model with . For simplicity, we assumed that the charge density is proportional to the energy density, namely, . It is demonstrated that the matter-geometry coupling constant β and charge parameter α affect the total gravitational mass and the radius of the star.

Pulsar PSR B0943$$+$$10 as an isotropic Vaidya–Tikekar-type compact star

In this paper, we have constructed a model for well behaved isotropic compact star in the presence of charged perfect fluid, by considering a static and spherically symmetric metric in Schwarzschild's canonical coordinate system. To put the resulting differential equations into a closed system, we have employed the Vaidya & Tikekar (J. Astrophys. Astron. 3:325, 1982) form of the metric potential grr. The resulting energy-momentum components, i.e., energy density and pressure contain six constants; two of these are determined through the junction condition (matching the interior with the exterior Schwarzschild solution) and by the property of vanishing pressure on the boundary. The remaining constants are constrained by requirements of a real compact star. The physical acceptability of our model is tested using the data of the pulsar PSR B0943+10. Using graphical analysis and tabular information we have shown that our model obeys all the physical requirements. The stability of this model is evaluated using the Tolman-Oppenheimer-Volkoff equation, the adiabatic index and the Harrison-Zeldovich-Novikov Criterion and it has passed the evaluation.

Two-fluid implementation in MPI-AMRVAC with applications to the solar chromosphere

Context. The chromosphere is a partially ionized layer of the solar atmosphere, which acts as the transition between the photosphere where the gas is almost neutral and the fully ionized corona. As the collisional coupling between neutral and charged particles decreases in the upper part of the chromosphere, the hydrodynamical timescales may become comparable to the collisional timescale, thus calling for the application of a two-fluid model. Aims. In this paper, we describe the implementation and validation of a two-fluid model that simultaneously evolves charges and neutrals, coupled by collisions. Methods. The two-fluid equations are implemented in the fully open-source MPI-AMRVAC code. In the photosphere and the lower part of the solar atmosphere, where collisions between charged and neutral particles are very frequent, an explicit time-marching would be too restrictive, since, to maintain stability, the time step needs to be proportional to the inverse of the collision frequency. This caveat can be overcome by evaluating the collisional terms implicitly, using an explicit–implicit (IMEX) scheme. Out of the various IMEX variants implemented, we focused on the IMEX-ARS3 scheme and we used it for all simulations presented in this paper. The modular structure of the code allows us to directly apply all other code functionality – in particular, its automated grid adaptivity – to the two-fluid model. Results. Our implementation recovers and significantly extends the available (analytic or numerical) test results for two-fluid chargeneutral evolutions. We demonstrate wave damping, propagation, and interactions in stratified settings, as well as Riemann problems for coupled plasma-neutral mixtures. We generalized a shock-dominated evolution from single to two-fluid regimes and made contact with recent findings on typical plasma-neutral instabilities. Conclusions. The cases presented here cover very different collisional regimes and our results are fully consistent with related findings from the literature. If collisional time and length scales are smaller than the hydrodynamical scales usually considered in the solar chromosphere, the density structures seen in the neutral and charged fluids will be similar, with the effect of elastic collisions between charges and neutrals shown to be similar to the effects of diffusivity. Otherwise, density structures are different and the decoupling in velocity between the two species increases, and neutrals may, for instance, show Kelvin–Helmholtz roll-up while the charges do not. The use of IMEX schemes efficiently avoids the small time step constraints of fully explicit implementations in strongly collisional regimes. Implementing an adaptive mesh refinement (AMR) greatly decreases the computational cost, as compared to uniform grid runs at the same effective resolution.

Explosive electrostatic instability of ferroelectric liquid droplets on ferroelectric solid surfaces

We investigated the electrostatic behavior of ferroelectric liquid droplets exposed to the pyroelectric field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal, in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase by reducing the temperature from the nematic phase, the liquid crystal droplets become electromechanically unstable and disintegrate by the explosive emission of fluid jets. These jets are mostly interfacial, spreading out on the substrate surface, and exhibit fractal branching out into smaller streams to eventually disrupt, forming secondary droplets. We understand this behavior as a manifestation of the Rayleigh instability of electrically charged fluid droplets, expected when the electrostatic repulsion exceeds the surface tension of the fluid. In this case, the charges are due to the bulk polarization of the ferroelectric fluid, which couples to the pyroelectric polarization of the underlying lithium niobate substrate through its fringing field and solid-fluid interface coupling. Since the ejection of fluid does not neutralize the droplet surfaces, they can undergo multiple explosive events as the temperature decreases.

A new class of charged spherically symmetric and static superdense star configurations

In this paper, we have obtained a new family of interior solutions of the Einstein–Maxwell field equations in general relativity for static, spherically symmetric distribution of charged fluid. The electric density is assumed to be [Formula: see text] where [Formula: see text] is a positive constant. The solution is well behaved for a wide range of [Formula: see text] hence, it is suitable for modeling a superdense star. The surface density is assumed to be [Formula: see text], for the validation of the solution set present, a comparison has also been made with the stars EXO 1785-248, SMC X-1, Her X-1, 4U 1538-52. For these particular stars, the maximum value of surface redshift is obtained to be 0.3251 for the star EXO 1785-248 and the minimum value is obtained as 0.2027 for the star Her X-1. We subject our solution to rigorous physical viability tests. In the absence of charge, we obtain the regular and well-behaved sixth model of Durgapal.

Incorporation of class I charged generalized polytropes with Karmarkar and complexity factor

In the present paper, we will incorporate three very useful aspects of astrophysics, generalized polytropes, Karmarkar condition and complexity factor to study the compact objects. For this purpose a charged anisotropic fluid distribution is used under static spherical symmetry. We develop a framework for class I generalized charged Lane–Emden equations for non-isothermal and isothermal regimes. Generalized polytropic equation of state with its two cases, mass density and energy density along with complexity factor lead us to the systems of differential equations and these systems are solved numerically. Finally, solutions of these systems are discussed graphically.

A study of charged stellar structure in modified f (R,ϕ,χ) gravity

The aim of this paper is to investigate and analyze the behavior of charged compact stars in the modified [Formula: see text] theory of gravity. When solving the field equations, we assume that Krori– Barua space-time describes the geometry of the inner space [K. Krori and J. Barua, A singularity-free solution for a charged fluid sphere in general relativity, J. Phys. A Math. Gen. 8 (1975) 508]. We further analyzed various physical characteristics for our model, including energy density, pressure components, anisotropy parameter, mass function, compactness element, and redshift through their graphical representations. Additionally, we have checked the equilibrium position by taking Tolman–Oppenheimer–Volkoff equation and stability by using Abreu’s criterion [H. Abreu, H. Hernandez, and L. Nunez, Sound speeds, cracking and the stability of self-gravitating anisotropic compact objects, Class. Quantum Grav. 24 (2007) 4631] and relativistic adiabatic index. For our study, we choose Hercules XI, Centaurus XIII, EXO 1785-248, LMC XIV stars for analysis.

Development of complexity induced frameworks for charged cylindrical polytropes

The main theme of this work is the development of complexity induced generalized frameworks for static cylindrical polytropes. We consider two different definitions of generalized polytopes with charged anisotropic inner fluid distribution. A new methodology based on complexity factor for the generation of consistent sets of differential equations will be presented. We conclude our work by carrying out graphical analysis of developed frameworks.