scholarly journals Oscillatory Convection in a Viscoelastic Fluid Layer in Hydromagnetics

1972 ◽  
Vol 25 (6) ◽  
pp. 695 ◽  
Author(s):  
PK Bhatia ◽  
JM Steiner
Keyword(s):  
Magnetic Field ◽  
Variational Principle ◽  
Viscoelastic Fluid ◽  
Fluid Layer ◽  
Horizontal Layer ◽  
Oscillatory Convection ◽  
Thermally Induced ◽  
Stabilizing Effect ◽  
The Magnetic Field ◽  
Proper Solutions

A study is made of the overstable mode of convection in an infinite horizontal layer of a viscoelastic fluid, heated from below, in the presence of a magnetic field. It is shown first that the problem is characterized by a variational principle. Proper solutions are then obtained for the case of two rigid boundaries using the variational method. It is found that the magnetic field has a stabilizing effect on the thermally induced overstability in a viscoelastic fluid, as in the case of an ordinary viscous fluid. The thermodynamic significance of the variational principle is also considered.

scholarly journals Effect of magnetic field on thermal instability of a rotating Rivlin-Ericksen viscoelastic fluid

2006 ◽  
Vol 2006 ◽  
pp. 1-10
Author(s):  
Pardeep Kumar ◽  
Hari Mohan ◽  
Roshan Lal
Keyword(s):  
Magnetic Field ◽  
Newtonian Fluid ◽  
Viscoelastic Fluid ◽  
Thermal Instability ◽  
Vertical Magnetic Field ◽  
Stationary Convection ◽  
Stabilizing Effect ◽  
The Stability ◽  
The Magnetic Field

The thermal instability of a rotating Rivlin-Ericksen viscoelastic fluid in the presence of uniform vertical magnetic field is considered. For the case of stationary convection, Rivlin-Ericksen viscoelastic fluid behaves like a Newtonian fluid. It is found that rotation has a stabilizing effect, whereas the magnetic field has both stabilizing and destabilizing effects. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. The rotation and magnetic field are found to introduce oscillatory modes in the system which were nonexistent in their absence.

The stability of viscous flow between rotating cylinders in the presence of a magnetic field

1953 ◽  
Vol 216 (1126) ◽  
pp. 293-309 ◽  
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Viscous Flow ◽  
Thermal Instability ◽  
Horizontal Layer ◽  
Rotational Stability ◽  
Marginal Stability ◽  
Inhibiting Effect ◽  
The Stability ◽  
The Magnetic Field

In this paper the theory of the stability of viscous flow between two rotating coaxial cylinders which has been developed by Taylor, Jeffreys and Meksyn is extended to the case when the fluid considered is an electrical conductor and a magnetic field along the axis of the cylinders is present. A differential equation of order eight is derived which governs the situation in marginal stability; and a significant set of boundary conditions for the problem is formulated. The case when the two cylinders are rotating in the same direction and the difference ( d ) in their radii is small compared to their mean (R 0 ) is investigated in detail. A variational procedure for solving the underlying characteristic value problem and determining the critical Taylor numbers for the onset of instability is described. As in the case of thermal instability of a horizontal layer of fluid heated below, the effect of the magnetic field is to inhibit the onset of instability, the inhibiting effect being the greater, the greater the strength of the field and the value of the electrical conductivity. In both cases, the inhibiting effect of the magnetic field depends on the strength of the field ( H ), the density ( ρ ) and the coefficients of electrical conductivity ( σ ), kinematic viscosity ( v ) and magnetic permeability ( μ ) through the same non-dimensional combination Q =μ 2 H 2 d 2 σ/ pv ; however, the effect on rotational stability is more pronounced than on thermal instability. A table of the critical Taylor numbers for various values of Q is provided.

scholarly journals Oscillatory convection in strong magnetic fields and origin of active regions

1968 ◽  
Vol 35 ◽  
pp. 127-130 ◽  
Author(s):  
S. I. Syrovatsky ◽  
Y. D. Zhugzhda
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Active Regions ◽  
Oscillatory Convection ◽  
Strong Magnetic Fields ◽  
Various Boundary Conditions ◽  
Convective Cells ◽  
The Magnetic Field ◽  
Polytropic Atmosphere

The convection in a compressible inhomogeneous conducting fluid in the presence of a vertical uniform magnetic field has been studied. It is shown that a new mode of oscillatory convection occurs, which exists in arbitrarily strong magnetic fields. The convective cells are stretched along the magnetic field, their horizontal dimensions are determined by radiative cooling. Criteria for convective instability in a polytropic atmosphere are obtained for various boundary conditions in the case when the Alfvén velocity is higher compared with the velocity of sound.The role of oscillatory convection in the origin of sunspots and active regions is discussed.

scholarly journals Magneto Convection in a Layer of Nanofluid With Soret Effect

2015 ◽  
Vol 9 (2) ◽  
pp. 63-69 ◽  
Author(s):  
Ramesh Chand ◽  
Gian Chand Rana
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Fluid Layer ◽  
Soret Effect ◽  
Lewis Number ◽  
Horizontal Layer ◽  
Diffusive Convection ◽  
Mode Method ◽  
Double Diffusive

AbstractDouble diffusive convection in a horizontal layer of nanofluid in the presence of uniform vertical magnetic field with Soret effect is investigated for more realistic boundary conditions. The flux of volume fraction of nanoparticles is taken to be zero on the isothermal boundaries. The normal mode method is used to find linear stability analysis for the fluid layer. Oscillatory convection is ruled out because of the absence of the two opposing buoyancy forces. Graphs have been plotted to find the effects of various parameters on the stationary convection and it is found that magnetic field, solutal Rayleigh number and nanofluid Lewis number stabilizes fluid layer, while Soret effect, Lewis number, modified diffusivity ratio and nanoparticle Rayleigh number destabilize the fluid layer.

scholarly journals Effect of Magnetic Field on Thermosolutal Instability of Rotating Ferromagnetic Fluid Under Varying Gravity Field

2021 ◽  
Vol 26 (1) ◽  
pp. 201-214
Author(s):  
S. K. Pundir ◽  
P. K. Nadian ◽  
R. Pundir
Keyword(s):  
Magnetic Field ◽  
Gravity Field ◽  
Fluid Layer ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Free Boundaries ◽  
Magnetic Field Rotation ◽  
Stabilizing Effect ◽  
Ferromagnetic Fluid ◽  
Solute Gradient

AbstractThis paper deals with the theoretical investigation of the effect of a magnetic field, rotation and magnetization on a ferromagnetic fluid under varying gravity field. To find the exact solution for a ferromagnetic fluid layer contained between two free boundaries, we have used a linear stability analysis and normal mode analysis method. For the case of stationary convection, a stable solute gradient has a stabilizing effect, while rotation has a stabilizing effect if λ>0 and destabilizing effect if λ<0. Further, the magnetic field is discovered to have both a stabilizing and destabilizing effect for both λ>0 and λ<0. It is likewise discovered that magnetization has a stabilizing effect for both λ>0 and λ<0 in the absence of the stable solute gradient. Graphs have been plotted by giving numerical values of various parameters. In the absence of rotation, magnetic field and stable solute gradient, the principle of exchange of stabilities is found to hold true for certain conditions.

scholarly journals Rayleigh-Bénard convection with magnetic field

2003 ◽  
pp. 29-40 ◽  
Author(s):  
Jürgen Zierep
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Fluid Layer ◽  
Wave Length ◽  
Critical Rayleigh Number ◽  
Black Spots ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Horizontal Fluid Layer ◽  
The Magnetic Field

We discuss the solution of the small perturbation equations for a horizontal fluid layer heated from below with an applied magnetic field either in vertical or in horizontal direction. The magnetic field stabilizes, due to the Lorentz force, more or less Rayleigh-B?nard convective cellular motion. The solution of the eigenvalue problem shows that the critical Rayleigh number increases with increasing Hartmann number while the corresponding wave length decreases. Interesting analogies to solar granulation and black spots phenomena are obvious. The influence of a horizontal field is stronger than that of a vertical field. It is easy to understand this by discussing the influence of the Lorentz force on the Rayleigh-B?nard convection. This result corrects earlier calculations in the literature.

scholarly journals DEPENDENCE OF MAXIMAL SENSITIVITY OF THE MAGNETIC FIELD HALL SENSORS BASED ON GRAPHENE ON TEMPERATURE

2021 ◽  
Vol 18 (3) ◽  
pp. 29-37
Author(s):  
І. Bolshakova ◽  
М. Strikha ◽  
Ya. Kost ◽  
F. Shurygin ◽  
Yu. Mykhashchuk ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Experimental Studies ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Thermally Induced ◽  
Temperature Range ◽  
Layer Graphene ◽  
Maximal Sensitivity ◽  
Hall Sensors ◽  
The Magnetic Field

A theory of graphene-based magnetic field Hall sensors sensitivity dependence on temperature is summarized. The existence of low-temperature range with sensitivity, almost independent on temperature, is predicted; at higher temperatures, when thermally-induced carrier concentration in graphene prevails, the sensitivity decreases with temperature. The experimental studies of the temperature dependence of magnetic sensitivity of Hall sensors on single layer graphene base were carried in temperature range from 300 °K to 430 °K. The values of sensitivity, obtained for room temperatures ~ 230 V·А‑1·Т‑1 exceed essentially the maximum sensitivity of the traditional Hall sensors on silicon base ~ 100  V·А‑1·Т‑1.

Magnetophoresis of microparticles in a magnetic liquid

2021 ◽  
pp. 99-105
Author(s):  
V.M. Polunin ◽  
◽  
P.A. Ryapolov ◽  
V.G. Bashtovoy ◽  
E.B. Postnikov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fluid ◽  
Fluid Layer ◽  
Inhomogeneous Magnetic Field ◽  
Magnetic Liquid ◽  
Reflection Of Light ◽  
Ring Magnet ◽  
And Diffusion ◽  
The Magnetic Field ◽  
Transmission And Reflection

An experimental setup has been developed for studying magnetophoresis in a layer of a magnetic fluid several millimeters thick by the method of transmission and reflection of light. In the experiment, we used the region of a ring magnet changing in sign of the magnetic field. The clarification of the central portion of the magnetic fluid layer, which is observed for several days, is interpreted by the fact that the concentration of particles is redistributed due to the processes of magnetophoresis of microparticles and diffusion of nanoparticles in an inhomogeneous magnetic field.

Thermal Instability of a Compressible and Partially Ionized Plasma

1986 ◽  
Vol 41 (5) ◽  
pp. 729-732 ◽  
Author(s):  
R. C. Sharma ◽  
J. N. Misra
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Specific Heat ◽  
Thermal Instability ◽  
Constant Pressure ◽  
Composite Medium ◽  
Sufficient Condition ◽  
Stabilizing Effect ◽  
Partially Ionized ◽  
The Magnetic Field

The compressibility and collisional effects on thermal instability of a composite medium are considered. The effect of compressibility is found to be stabilizing. In contrast to the nonoscillatory modes for (Cp/g) ß > 1 in the absence of a magnetic field, Cp, ß and g being the specific heat at constant pressure, a uniform adverse temperature gradient and the acceleration due to gravity respectively, the presence of a magnetic field introduces oscillatory modes in the system. The sufficient condition for non-existence of overstability is found. The magnetic field is found to have a stabilizing effect on the system for (Cp/g) ß > 1.

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