Mean Electromotive Force Due to Magnetoconvection in Rotating Horizontal Layer in Dependence on Boundary Conditions

1993 ◽  
pp. 457-461
Author(s):  
J. Brestenský ◽  
S. Ševčík ◽  
L. Rosenberg
Keyword(s):  
Boundary Conditions ◽  
Electromotive Force ◽  
Horizontal Layer

scholarly journals Mean Electromotive Force Due to Magnetoconvection in Rotating Horizontal Layer in Dependence on Boundary Conditions

1993 ◽  
Vol 157 ◽  
pp. 457-461
Author(s):  
J. Brestenský ◽  
S. Ševčík ◽  
L. Rosenberg
Keyword(s):  
Boundary Conditions ◽  
Vertical Axis ◽  
Horizontal Layer ◽  
Rigid Surface ◽  
Uniform Temperature ◽  
Azimuthal Magnetic Field ◽  
Electrically Conducting ◽  
Various Boundary Conditions ◽  
Electrically Conducting Fluid ◽  
Ponderomotive Forces

The instability due to a vertical uniform temperature gradient is studied in a rapidly rotating horizontal layer of an electrically conducting fluid permeated by an azimuthal magnetic field linearly growing with the distance from the vertical axis of rotation. In addition to the boundary conditions used in So ward's study (1979), that is, force-free surface and perfect electrical and thermal conductivity outside, also other conditions more realistic for the Earth's core are considered, that is, rigid surface and electrically insulating walls. Using the concept of meanfield mlid mean electromotive and ponderomotive forces (E.M.F. and P.M.F.) are calculated and compared for various boundary conditions. The dependence of the E.M.F. and P.M.F. on the electromagnetic boundary conditions is strong (slight) if the boundaries are free (rigid).

The Onset of Convection in an Internally Heated Nanofluid Layer

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
D. A. Nield ◽  
A. V. Kuznetsov
Keyword(s):  
Brownian Motion ◽  
Boundary Conditions ◽  
Microwave Heating ◽  
Chemical Reaction ◽  
Vertical Gradient ◽  
Horizontal Layer ◽  
Internal Heating ◽  
Onset Of Convection ◽  
Brownian Motion And Thermophoresis ◽  
Heating From Below

We analytically studied the onset of convection, induced by internal heating, such as that produced by microwave heating or chemical reaction, in a horizontal layer of a nanofluid subject to Brownian motion and thermophoresis. This is a fundamentally different situation from traditionally studied heating from below. Convection, when it occurs, is now concentrated in the portion of the layer where the upward vertical gradient is negative, which is the upper portion of the layer. The situation of internal heating also allows employing more realistic boundary conditions than those hitherto used.

The thermohaline Rayleigh-Jeffreys problem

1967 ◽  
Vol 29 (3) ◽  
pp. 545-558 ◽  
Author(s):  
D. A. Nield
Keyword(s):  
Rayleigh Number ◽  
Boundary Conditions ◽  
Numerical Solutions ◽  
Stability Boundary ◽  
Boundary Curve ◽  
Solute Concentration ◽  
Horizontal Layer ◽  
Wave Number ◽  
Convection Cell ◽  
Onset Of Convection

The onset of convection induced by thermal and solute concentration gradients, in a horizontal layer of a viscous fluid, is studied by means of linear stability analysis. A Fourier series method is used to obtain the eigenvalue equation, which involves a thermal Rayleigh numberRand an analogous solute Rayleigh numberS, for a general set of boundary conditions. Numerical solutions are obtained for selected cases. Both oscillatory and monotonic instability are considered, but only the latter is treated in detail. The former can occur when a strongly stabilizing solvent gradient is opposed by a destablizing thermal gradient. When the same boundary equations are required to be satisfied by the temperature and concentration perturbations, the monotonic stability boundary curve in the (R, S)-plane is a straight line. Otherwise this curve is concave towards the origin. For certain combinations of boundary conditions the critical value ofRdoes not depend onS(for some range ofS) or vice versa. This situation pertains when the critical horizontal wave-number is zero.A general discussion of the possibility and significance of convection at ‘zero’ wave-number (single convection cell) is presented in an appendix.

scholarly journals Investigation of convective structures and phase transition induced by non-stationary boundary conditions in a horizontal layer of water

2019 ◽  
Author(s):  
Виталий Арбузов ◽  
Vitaliy Arbuzov ◽  
Эдуард Арбузов ◽  
Eduard Arbuzov ◽  
Владимир Бердников ◽  
...  
Keyword(s):  
Phase Transition ◽  
Boundary Conditions ◽  
Water Layer ◽  
Horizontal Layer ◽  
Temperature Fields ◽  
Special Importance ◽  
Stationary Boundary ◽  
Convective Structures ◽  
Numerical Simulation Methods ◽  
Lower Heat

The evolution of convective structures and the phase transition induced by non-stationary boundary conditions in a horizontal water layer bounded by flat heat-exchange surfaces were studied by shear interferometry and numerical simulation methods. Numerical modeling of the temperature field as a field of isotherms in the mode of monotonous cooling of horizontal walls was performed. The problem of fragmentary reconstruction of hilbertograms and shear interferograms images from a numerical model of the isotherm field was solved. The hydrodynamics of convective currents, the coevolution of temperature fields, interference and Hilbert structures have been modeled and studied taking into account the inversion of water density in the vicinity of the isotherm (+4°C), under conditions of phase transition and growth of the ice layer on the lower heat transfer plane. The simulation was performed using a proprietary software package. The relevance of this kind of research is due to the special importance of convection in geodynamics, physics of the atmosphere and the ocean, in hydrodynamic and thermophysical processes associated with the formation and growth of crystals.

Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

1970 ◽  
Vol 28 ◽  
pp. 360-361
Author(s):  
John W. Coleman
Keyword(s):  
Boundary Conditions ◽  
High Performance ◽  
Force Fields ◽  
Optical Design ◽  
Direct Conversion ◽  
Design Engineering ◽  
Design Data ◽  
Scalar Potentials ◽  
Geometric Elements ◽  
At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

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