scholarly journals Nonlinear Thermal Convection in a Layer with Imposed Energy Flux

1974 ◽  
Vol 27 (4) ◽  
pp. 481 ◽  
Author(s):  
R Van der Borght
Keyword(s):  
Boundary Conditions ◽  
Energy Flux ◽  
Thermal Convection ◽  
Average Energy ◽  
Finite Amplitude ◽  
Solar Granulation ◽  
Convective Motions ◽  
Rayleigh Numbers

Results are reported of an investigation into the effect of the chosen boundary conditions on the steady finite-amplitude convective motions in a layer in which the average energy flux is imposed. The boundary conditions are chosen with a view to the application of the results to solar granulation and supergranulation. It is shown that, at high Rayleigh numbers, solutions do in fact exist for which there is no modulation in the energy flux and little fluctuation in the temperature across the boundaries.

Incipient Buoyant Thermal Convection in a Vertical Cylindrical Annulus

1990 ◽  
Vol 112 (4) ◽  
pp. 959-964 ◽  
Author(s):  
D. L. Littlefield ◽  
P. V. Desai
Keyword(s):  
Rayleigh Number ◽  
Boundary Conditions ◽  
Thermal Convection ◽  
Fluid Motion ◽  
Radius Ratio ◽  
Cellular Behavior ◽  
Cylindrical Annulus ◽  
Rayleigh Numbers ◽  
Number Of Cells

The incipient buoyant thermal convection in a vertical cylindrical annulus when heated from below is examined. The ends are assumed to be free, and the sidewalls perfectly conducting. The temperature needed to initiate fluid motion is expressed nondimensionally in terms of the Rayleigh number. The analytical conflict that arises for annuli of infinite aspects ratios due to insufficient independent boundary conditions is resolved. Calculations for the critical Rayleigh numbers are presented for a variety of geometries, and the corresponding velocity and temperature perturbations are also shown. The number of cells increases as the aspect and radius ratio decrease with a strong bias towards the development of azimuthally varying cells. These changes in cellular behavior are expected based on physical justifications and comparisons with previous studies.

National primary standard of air kerma, air kerma rate, exposure, exposure rate and energy flux for X-rays and gamma radiation GET 8-2019

2020 ◽  
pp. 8-12
Author(s):  
Alexandr V. Oborin ◽  
Anna Y. Villevalde ◽  
Sergey G. Trofimchuk
Keyword(s):  
Gamma Radiation ◽  
Energy Flux ◽  
Primary Standard ◽  
Average Energy ◽  
Ion Pair ◽  
X Rays ◽  
Exposure Rate ◽  
Ionization Chambers ◽  
Air Kerma ◽  
Air Kerma Rate

The results of development of the national primary standard of air kerma, air kerma rate, exposure, exposure rate and energy flux for X-rays and gamma radiation GET 8-2011 in 2019 are presented according to the recommendations of the ICRU Report No. 90 “Key Data for Ionizing-Radiation Dosimetry: Measurement Standards and Applications”. The following changes are made to the equations for the units determination with the standard: in the field of X-rays, new correction coefficients of the free-air ionization chambers are introduced and the relative standard uncertainty of the average energy to create an ion pair in air is changed; in the field of gamma radiation, the product of the average energy to create an ion pair in air and the electron stopping-power graphite to air ratio for the cavity ionization chambers is changed. More accurate values of the units reproduced by GET 8-2019 are obtained and new metrological characteristics of the standard are stated.

scholarly journals Rotating turbulent thermal convection at very large Rayleigh numbers

2021 ◽  
Vol 912 ◽  
Author(s):  
Marcel Wedi ◽  
Dennis P.M. van Gils ◽  
Eberhard Bodenschatz ◽  
Stephan Weiss
Keyword(s):  
Thermal Convection ◽  
Rayleigh Numbers

Abstract

Thermal convection in the porous methane-soaked regolith in Titan: Finite amplitude convection

Icarus ◽  
2012 ◽  
Vol 217 (1) ◽  
pp. 130-143 ◽  
Author(s):  
Leszek Czechowski ◽  
Konrad J. Kossacki
Keyword(s):  
Thermal Convection ◽  
Finite Amplitude

Sidewall finite-conductivity effects in confined turbulent thermal convection

2002 ◽  
Vol 473 ◽  
pp. 201-210 ◽  
Author(s):  
ROBERTO VERZICCO
Keyword(s):  
Boundary Conditions ◽  
Thermal Convection ◽  
Lateral Wall ◽  
Finite Conductivity ◽  
Mean Flow ◽  
Number Range ◽  
Additional Heat ◽  
Low Aspect Ratio ◽  
Temperature Boundary ◽  
The Mean

The effects of a sidewall with finite thermal conductivity on confined turbulent thermal convection has been investigated using direct numerical simulation. The study is motivated by the observation that the heat flowing through the lateral wall is not always negligible in the low-aspect-ratio cells of several recent experiments. The extra heat flux modifies the temperature boundary conditions of the flow and therefore the convective heat transfer. It has been found that, for usual sidewall thicknesses, the heat travelling from the hot to the cold plates directly through the sidewall is negligible owing to the additional heat exchanged at the lateral fluid/wall interface. In contrast, the modified temperature boundary conditions alter the mean flow yielding significant Nusselt number corrections which, in the low Rayleigh number range, can change the exponent of the Nu vs. Ra power law by 10%.

scholarly journals Waves in Microstructured Conducting Sheath Helix Embedded Optical Guides with Chiral Nihility and Chiral Materials

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
N. Iqbal ◽  
M. A. Baqir ◽  
P. K. Choudhury
Keyword(s):  
Boundary Conditions ◽  
Flux Density ◽  
Energy Flux ◽  
Pitch Angle ◽  
Electromagnetic Waves ◽  
The Core ◽  
Dispersion Behavior ◽  
Chiral Materials ◽  
Energy Flux Density

The paper deals with the sustainment of electromagnetic waves in circularly cylindrical optical guide with chiral nihility and chiral materials in the core and the clad sections, respectively. A perfectly conducting tightly wound helix is introduced at the core-clad interface. The eigenvalue relation for such a complex optical microstructured guide is deduced by applying suitable boundary conditions at the core-clad interface, and the dispersion behavior is analyzed by varying the pitch angle of helix. The sustainment of energy flux density in such optical guides is estimated under various structural conditions, and the density patterns in core-clad sections are anatomized analytically.

Boundary conditions for Maxwell fields in Kerr-AdS spacetimes

2016 ◽  
Vol 25 (09) ◽  
pp. 1641011 ◽  
Author(s):  
Mengjie Wang
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Boundary Conditions ◽  
Energy Flux ◽  
Momentum Flux ◽  
De Sitter ◽  
Perturbative Methods ◽  
Flux Boundary Conditions ◽  
Maxwell Fields ◽  
New Type

Perturbative methods are useful to study the interaction between black holes and test fields. The equation for a perturbation itself, however, is not complete to study such a composed system if we do not assign physically relevant boundary conditions. Recently we have proposed a new type of boundary conditions for Maxwell fields in Kerr-anti-de Sitter (Kerr-AdS) spacetimes, from the viewpoint that the AdS boundary may be regarded as a perfectly reflecting mirror, in the sense that energy flux vanishes asymptotically. In this paper, we prove explicitly that a vanishing energy flux leads to a vanishing angular momentum flux. Thus, these boundary conditions may be dubbed as vanishing flux boundary conditions.

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