scholarly journals Gravitational Instability of Rotating Viscoelastic Partially Ionized Plasma in the Presence of an Oblique Magnetic Field and Hall Current

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
M. F. El-Sayed ◽  
R. A. Mohamed
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
Hall Current ◽  
Gravitational Instability ◽  
Angular Frequency ◽  
Physical Parameters ◽  
Physical Effects ◽  
Partially Ionized ◽  
The Magnetic Field ◽  
Oblique Magnetic Field

The gravitational instability of a rotating Walters B′ viscoelastic partially ionized plasma permeated by an oblique magnetic field has been investigated in the presence of the effects of Hall currents, electrical resistivity, and ion viscosity. The dispersion relation and numerical calculations have been performed to obtain the dependence of the growth rate of the gravitational unstable mode on the various physical effects. It is found that viscosity and collision frequency of plasma have stabilizing effects, while viscoelasticity and angular frequency of rotation have destabilizing effect; the electrical resistivity has a destabilizing effect only for small wavenumbers; the density of neutral particles and the magnetic field component in z-direction have stabilizing effects for wavenumbers ranges k<5 and k<10, respectively; the Hall current has a slightly destabilizing effect. Finally, the inclination angle to z-direction has a destabilizing effect to all physical parameters.

scholarly journals Hall current, Newtonian heating and second-order slip effects on convective magneto-micropolar fluid flow over a sheet

2018 ◽  
Vol 29 (09) ◽  
pp. 1850090 ◽  
Author(s):  
Muhammad Kamran ◽  
Benchawan Wiwatanapataphee ◽  
Kuppalapalle Vajravelu
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Fluid Flow ◽  
Micropolar Fluid ◽  
Hall Current ◽  
Shrinking Sheet ◽  
Physical Parameters ◽  
Newtonian Heating ◽  
Micropolar Fluid Flow ◽  
The Magnetic Field

This research deals with an analysis of the Hall current effect on the mixed convective magneto-micropolar fluid flow over a permeable stretching/shrinking sheet. Impact of the Newtonian heating parameter is analyzed in the slip flow regime. The nonlinear equations of the fluid flow are derived with the help of a similarity transform and its solutions are obtained by Optimal Homotopy Analysis Method (OHAM). For limiting cases, obtained results are in excellent agreement with the available exact and numerical results in the literature. The graphical and tabular representations of the obtained results show significant effects of the physical parameters on the magneto-micropolar fluid flow and heat transfer characteristics. In particular, it is observed that, as the sheet stretches, a change in the Hall current parameter yields a higher horizontal velocity component for the lower value of the magnetic field parameter; while it produces a higher and shorter transverse velocity profile at high intensity of the magnetic field. In Magnetohydrodynamics (MHD) generators, Hall effects are an important consideration to analyze the heat transfer phenomenon with high temperature conducting fluids.

HEXAGON-STRIPE TRANSITION AT THE MAGNETIC FIELD INDUCED PHASE TRANSFORMATIONS OF THE MAGNETORHEOLOGICAL SUSPENSIONS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2345-2351 ◽  
Author(s):  
A. CEBERS
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Physical Parameters ◽  
Phase Boundaries ◽  
Modulated Phases ◽  
Magnetorheological Suspensions ◽  
Perturbed State ◽  
Magnetorheological Suspension ◽  
The Magnetic Field ◽  
Hele Shaw Cell

The phase diagram of the magnetorheological suspension allowing for the modulated phases in the Hele-Shaw cell under the action of the normal field is calculated. The phase boundaries between the stripe, the hexagonal and the unmodulated phases in dependence on the layer thickness and the magnetic field strength are found. The existence of the transitions between the stripe and the hexagonal phases at the corresponding variation of the physical parameters is illustrated by the numerical simulation of the concentration dynamics in the Hele-Shaw cell. It is remarked that those transitions in the case of the magnetorheological suspensions can be caused by the compression or the expansion of the layer. Among the features noticed at the numerical simulation of the concentration dynamics in the Hele-Shaw cell are: the stripe patterns formed from the preexisting hexagonal structures are more ordered than arising from the initial randomly perturbed state; at the slightly perturbed boundary between the concentrated and diluted phases the hexagonal and the inverted hexagonal phases are formed and others.

Effects of Ca2+-Doping on the Crystal Lattice of α-Fe2O3

2014 ◽  
Vol 975 ◽  
pp. 116-121
Author(s):  
Bruna da Costa Andrade ◽  
José Cleverton da Conceição Passos ◽  
Marcelo Andrade Macedo
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
Crystal Lattice ◽  
Coercive Field ◽  
Calcium Concentration ◽  
Sol Gel ◽  
Impedance Analysis ◽  
Hematite Phase ◽  
Sol Gel Process ◽  
The Magnetic Field

Samples of CayFe12-yO19 (0 ≤ y ≤ 1.0) were prepared by a proteic sol–gel process with hematite phase and clusters of M-type calcium hexaferrite. Impedance analysis showed that the resistivity increased with calcium concentration in the 0.0 < y ≤ 0.2 range, but decreased for y > 0.2. The saturation of the electrical resistivity occurred at 7.5 × 106 Ω·cm for Ca0.9Fe11.1O19. The plot of magnetization as a function of the magnetic field showed high values of saturation magnetization (40 emu/g) with low remanence (6.7 emu/g) and coercive field (320 Oe).

scholarly journals Stability analysis of magnetic fluids in the presence of an oblique field and mass and heat transfer

2020 ◽  
Vol 330 ◽  
pp. 01035
Author(s):  
Rabah Djeghiour ◽  
Bachir Meziani
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Fluids ◽  
Physical Parameters ◽  
Stability Diagrams ◽  
Stability And Instability ◽  
Mass And Heat Transfer ◽  
Model Equations ◽  
The Stability ◽  
Oblique Magnetic Field

In this paper, we investigate an analysis of the stability of a basic flow of streaming magnetic fluids in the presence of an oblique magnetic field is made. We have use the linear analysis of modified Kelvin-Helmholtz instability by the addition of the influence of mass transfer and heat across the interface. Problems equations model is presented where nonlinear terms are neglected in model equations as well as the boundary conditions. In the case of a oblique magnetic field, the dispersion relation is obtained and discussed both analytically and numerically and the stability diagrams are also obtained. It is found that the effect of the field depends strongly on the choice of some physical parameters of the system. Regions of stability and instability are identified. It is found that the mass and heat transfer parameter has a destabilizing influence regardless of the mechanism of the field.

Numerical and Statistical Analysis of Dissipative and Heat Absorbing Graphene Maxwell Nanofluid Flow Over a Stretching Sheet

2021 ◽  
Vol 10 (4) ◽  
pp. 600-607
Author(s):  
A. Bhattacharyya ◽  
R. Sharma ◽  
M. K. Mishra ◽  
Ali J. Chamkha ◽  
E. Mamatha
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Numerical Solution ◽  
Physical Parameters ◽  
Nonlinear Mathematical Model ◽  
Nanofluid Flow ◽  
Maxwell Nanofluid ◽  
Highly Nonlinear ◽  
Numeric Data ◽  
The Magnetic Field

This paper is basically devoted to carry out an investigation regarding the unsteady flow of dissipative and heat absorbing hydromagnetic graphene Maxwell nanofluid over a linearly stretched sheet taking momentum and thermal slip conditions into account. Ethylene glycol is selected as a base fluid while graphene particles are considered as nanoparticles. The highly nonlinear mathematical model of the problem is converted into a set of nonlinear coupled differential equations by means of fitting similarity variables. Further, Runge-Kutta Fehlberg algorithms along with the shooting scheme are instigated to analyse the numerical solution. The variations in graphene Maxwell nanofluid velocity and temperature owing to different physical parameters have been demonstrated via numerous graphs whereas Nusselt number and skin friction coefficients are illustrated in numeric data form and are reported in different tables. In addition, a statistical method is implemented for multiple quadratic regression estimation analysis on the numerical figures of wall velocity gradient and local Nusselt number to establish the connection among heat transfer rate and physical parameters. Our numerical findings reveal that the magnetic field, unsteadiness, inclination angle of magnetic field and porosity parameters boost the graphene Maxwell nanofluid velocity while Maxwell parameter has a reversal impact on it. The regression analysis confers that Nusselt number is more prone to heat absorption parameter as compared to Eckert number. Finally, the numerical findings are compared with those of earlier published articles under restricted conditions to validate the numerical solution. The comparison of numerical findings shows an excellent conformity among the results.

In Search of the Jerk Element

2021 ◽  
Author(s):  
Zachary P. Belyaev ◽  
Samuel N. Downes ◽  
Philip A. Voglewede
Keyword(s):  
Magnetic Field ◽  
Motion Planning ◽  
System Performance ◽  
Theoretical Background ◽  
Physical Parameters ◽  
Common Elements ◽  
Planning And Control ◽  
Magneto Rheological ◽  
And Control ◽  
The Magnetic Field

Abstract Mechanical components, such as springs, dampers and mass, alter and influence an engineered system’s motion based upon a system’s position, velocity and acceleration, respectively. This paper aims to discover and develop another element (dubbed the damper) which provides a force proportional to a system’s jerk (i.e., the derivative of acceleration) to better engineer a system’s response. By utilizing the known applications of jerk in motion planning and control theory, existing possible physical implementations and uses of jerk and the jerk element are discussed in relation to its influence on the system’s response, specifically vibration. Using a Buckingham Pi approach, the theoretical background of the jerk element is presented and possible physical parameters are combined to show how the jerk element could be created from common elements and parameters. The most promising approach of varying the magnetic field of existing magneto-rheological dampers is developed to give an example of the jerk element along with the difficulties and concerns in developing the jerk element. This paper serves less of a purpose towards answering all questions of the jerk element, but rather focuses more on posing the appropriate questions which sets the stage for an easily realizable future jerk element which can improve system performance.

scholarly journals Rapid and efficient mass collection by a supersonic cloud–cloud collision as a major mechanism of high-mass star formation

2020 ◽  
Author(s):  
Yasuo Fukui ◽  
Tsuyoshi Inoue ◽  
Takahiro Hayakawa ◽  
Kazufumi Torii
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Gravitational Instability ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Mass Star ◽  
Major Mechanism ◽  
Dense Cores ◽  
The Magnetic Field

Abstract A supersonic cloud–cloud collision produces a shock-compressed layer which leads to formation of high-mass stars via gravitational instability. We carried out a detailed analysis of the layer by using the numerical simulations of magneto-hydrodynamics which deal with colliding molecular flows at a relative velocity of 20 km s−1 (Inoue & Fukui 2013, ApJ, 774, L31). Maximum density in the layer increases from 1000 cm−3 to more than 105 cm−3 within 0.3 Myr by compression, and the turbulence and the magnetic field in the layer are amplified by a factor of ∼5, increasing the mass accretion rate by two orders of magnitude to more than 10−4 $ M_{\odot } $ yr−1. The layer becomes highly filamentary due to gas flows along the magnetic field lines, and dense cores are formed in the filaments. The massive dense cores have size and mass of 0.03–0.08 pc and 8–$ 50\, M_{\odot } $ and they are usually gravitationally unstable. The mass function of the dense cores is significantly top-heavy as compared with the universal initial mass function, indicating that the cloud–cloud collision preferentially triggers the formation of O and early B stars. We argue that the cloud–cloud collision is a versatile mechanism which creates a variety of stellar clusters from a single O star like RCW 120 and M 20 to tens of O stars of a super star cluster like RCW 38 and a mini-starburst W 43. The core mass function predicted by the present model is consistent with the massive dense cores obtained by recent ALMA observations in RCW 38 (Torii et al. 2021, PASJ, in press) and W 43 (Motte et al. 2018, Nature Astron., 2, 478). Considering the increasing evidence for collision-triggered high-mass star formation, we argue that cloud–cloud collision is a major mechanism of high-mass star formation.

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