Viscomagnetic Heat Flux Experiments as a Test of Gas Kinetic Theory in the Burnett Regime

1978 ◽  
Vol 33 (7) ◽  
pp. 749-760 ◽  
Author(s):  
G. E. J. Eggermont ◽  
P. W. Hermans ◽  
L. J. F. Hermans ◽  
H. F. P. Knaap ◽  
J. J. M. Beenakker
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Heat Flux ◽  
External Magnetic Field ◽  
Room Temperature ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Gas Kinetic Theory ◽  
The Magnetic Field ◽  
Good Agreement

In a rarefied polyatomic gas streaming through a rectangular channel, an external magnetic field produces a heat flux perpendicular to the flow direction. Experiments on this “viscom agnetic heat flux” have been performed for CO, N2, CH4 and HD at room temperature, with different orientations of the magnetic field. Such measurements enable one to separate the boundary layer contribution from the purely bulk contribution by means of the theory recently developed by Vestner. Very good agreement is found between the experimentally determined bulk contribution and the theoretical Burnett value for CO, N2 and CH4 , yet the behavior of HD is found to be anomalous.

Enhancement of Heat Transfer in Miniaturized Channels Using Ferrohydrodynamic Convection

2003 ◽  
Author(s):  
Ranjan Ganguly ◽  
Swarnendu Sen ◽  
Ishwar K. Puri
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
External Magnetic Field ◽  
Rectangular Channel ◽  
Colloidal Dispersion ◽  
Electronic Cooling ◽  
Fluid Temperature ◽  
Heat Transfer Augmentation ◽  
Nusselt Numbers ◽  
The Magnetic Field

Heat transfer in miniaturized channels and slots in electronic cooling applications is restricted by relatively low convection due to flow limitations. The flow is generally laminar and heat transfer in these small geometries is usually conduction limited. We have proposed the use of ferrofluids as coolants in the presence of a nonuniform external magnetic field to enhance the heat transfer. A magnetic ferrofluid consists of a stable colloidal dispersion of subdomain magnetic nanoparticles in a liquid carrier that remain suspended due to their thermal Brownian energy. Under a varying external magnetic field (B), a ferrofluid experiences a local volumetric body force (M.∇)B. The magnetization M of the ferrofluid is coupled with the fluid temperature through its density and magnetic susceptibility. In our simulations, a strong magnetic field is considered to be applied by placing an edge pole adjacent to one of the walls of a rectangular channel. The channel is assumed to carry a pressure-driven ferrofluid flow. The resulting flowfield is predicted by numerically solving the coupled mass, momentum, energy, and Maxwell’s equations. A parametric study is performed to identify the influence of the magnetic field strength on the temperature distribution and the resulting heat transfer. A comparison based on the local and average Nusselt numbers shows that there is a significant heat transfer augmentation due to the magnetic field.

CGL Invariants and the Moments of the Boltzmann–Vlasov Equation

1974 ◽  
Vol 52 (14) ◽  
pp. 1345-1357 ◽  
Author(s):  
M. Fridman
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Solar Wind ◽  
Vlasov Equation ◽  
Gyration Radius ◽  
Solar Wind Parameters ◽  
Essential Problem ◽  
The Magnetic Field ◽  
Transport Laws ◽  
Good Agreement

The transport laws of the noncollisional systems must be obtained from the Boltzmann–Vlasov equation. The most simple cases are the CGL invariants along the magnetic field. The essential problem is to determine the criteria necessary to close the moments system. The lower order in the gyration radius expansion gives the perpendicular contribution to the heat flux. After expansion with the supersonic conditions, the parallel contribution is obtained, and also the second term of the expansions in which the first term is the "invariant." The numerical value of the heat flux can be considered in good agreement with the solar wind parameters, and the corrections to the invariants are found to agree with previous results (kinetical and 20-moments Grad approximation).

scholarly journals Electrochemical Performance of Iron Oxide Nanoflakes on Carbon Cloth under an External Magnetic Field

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 939
Author(s):  
Lei Geng ◽  
Zenglai Gao ◽  
Qibo Deng
Keyword(s):  
Magnetic Field ◽  
Iron Oxide ◽  
External Magnetic Field ◽  
Electrochemical Performance ◽  
Electrochemical Properties ◽  
Room Temperature ◽  
Aqueous Electrolyte ◽  
Carbon Cloth ◽  
Polarization Phenomenon ◽  
The Magnetic Field

In this work, the iron oxide (Fe2O3) nanoflakes on carbon cloth (Fe2O3@CC) were triumphantly prepared and served as the electrode of supercapacitors. By applying an external magnetic field, we first find that the magnetic field could suppress the polarization phenomenon of electrochemical performance. Then, the influences of the mono-/bi-valent cations on the electrochemical properties of the Fe2O3@CC were investigated under a large external magnetic field (1 T) in this work. The chemical valences of the cations in the aqueous electrolytes (LiNO3 and Ca(NO3)2) have almost no influences on the specific capacitance at different scan rates. As one of important parameters to describe the electrochemical properties, the working potential window of the Fe2O3@CC electrode was also investigated in this work. The broad potential window in room-temperature molten salt (LiTFSI + LiBETI (LiN(SO2CF3)2 + LiN(SO2C2F5)2)) has been obtained and reached 1.2 V, which is higher than that of the traditional aqueous electrolyte (~0.9 V).

FARADAY AND MAGNETIC KERR ROTATION MEASUREMENTS ON Co AND Ni FILMS AROUND M2,3 EDGES

2002 ◽  
Vol 09 (02) ◽  
pp. 943-947 ◽  
Author(s):  
KATSUHIKO SAITO ◽  
MITSUAKI IGETA ◽  
TAKEO EJIMA ◽  
TADASHI HATANO ◽  
MAKOTO WATANABE
Keyword(s):  
Magnetic Field ◽  
Room Temperature ◽  
Permanent Magnets ◽  
Magnetic Circular Dichroism ◽  
Single Layer ◽  
Kerr Rotation ◽  
The Difference ◽  
Kerr Rotation Angle ◽  
The Magnetic Field ◽  
Good Agreement

Faraday and longitudinal magnetic Kerr rotation measurements were performed on Co and Ni single layer films around their M2,3 edges, at room temperature under an applied magnetic field of 0.82 T generated by a magnetic circuit composed of permanent magnets. The longitudinal Kerr rotation angle spectra are in good agreement with those calculated from the Faraday rotation spectra in Ni but different in Co. The main reason for the difference in Co was explained with the difference of the magnetization between a longitudinal Kerr (saturated) and a Faraday (unsaturated) configuration under the magnetic field of 0.82 T. This was supported by the calculated result from magnetic circular dichroism (1.2 T, 140 K) measurement on Co.

scholarly journals Experimental and Numerical Investigation of 2A16 Aluminum and Pure Copper Magnetic Assisted Dissimilar Laser Wire Feed Welding Brazing

2021 ◽  
Author(s):  
Zhengtian Wang ◽  
Shuyuan Jiang ◽  
Yiping Chen ◽  
Zhenyu Xiong ◽  
Dean Hu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Flow Direction ◽  
Pure Copper ◽  
Three Dimensional ◽  
Weld Bead ◽  
Magnetic Flux Density ◽  
Full Factorial ◽  
The Magnetic Field ◽  
Wire Feed ◽  
Good Agreement

Abstract Magnetic field assisted welding could suppress defects and improve weld bead properties obviously. In this paper, a full factorial experiment with coaxial magnetic field assisted welding was conducted to study the mechanism of the magnetic field on the dissimilar laser wire feed welding brazing profile of aluminum and copper. Furthermore, a three dimensional numerical simulation model was developed to reveal the influence of the magnetic field on the weld bead. It was found that with the magnetic flux density increase from 10 mT to 50 mT, the properties of the weld bead were improved significantly, and the wetting angle decreased from 53°to 26°, the main fluid flow direction of the weld bead changed in to horizontal direction. Meanwhile, EDS and XRD results showed that the main intermetallic compounds (IMC) of Al2Cu and CuZn composition changed to Al4.2Cu3.2Zn0.7 in welding beads. Computed and measured distortions illustrated good agreement in the fusion zone.

scholarly journals Resonant damping and instability of propagating kink waves in flowing and twisted magnetic flux tubes

2020 ◽  
Vol 496 (1) ◽  
pp. 67-79 ◽  
Author(s):  
K Bahari ◽  
N S Petrukhin ◽  
M S Ruderman
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Flow Direction ◽  
Flow Speed ◽  
Wave Frequency ◽  
Transitional Layer ◽  
Kink Wave ◽  
Kink Waves ◽  
Field Lines ◽  
The Magnetic Field

ABSTRACT We study the propagation and stability of kink waves in a twisted magnetic tube with the flow. The flow velocity is assumed to be parallel to the magnetic field, and the magnetic field lines are straight outside the tube. The density is constant inside and outside of the tube, and it monotonically decreases from its value inside the tube to that outside in the transitional or boundary layer. The flow speed and magnetic twist monotonically decrease in the transitional layer from their values inside the tube to zero outside. Using the thin tube and thin boundary layer (TTTB) approximation, we derived the dispersion equation determining the dependence of the wave frequency and decrement/increment on the wavenumber. When the kink wave frequency coincides with the local Alfvén frequency at a resonant surface inside the transitional layer, the kink wave is subjected to either resonant damping or resonant instability. We study the properties of kink waves in a particular unperturbed state where there is no flow and magnetic twist in the transitional layer. It is shown that in a tube with flow, the kink waves can propagate without damping for particular values of the flow speed. Kink waves propagating in the flow direction either damp or propagate without damping. Waves propagating in the opposite direction can either propagate without damping, or damp, or become unstable. The theoretical results are applied to the problem of excitation of kink waves in spicules and filaments in the solar atmosphere.

The Effect of Magnetic Field on the Hydration of Nanoscopic Hydrophobic N-Alkane Plates

2011 ◽  
Vol 228-229 ◽  
pp. 1007-1011
Author(s):  
Wei Wei Zhang ◽  
Long Qiu Li ◽  
Guang Yu Zhang ◽  
Hui Juan Dong
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Dynamics Simulation ◽  
Free Energy Barrier ◽  
Confined Water ◽  
Magnetic Exposure ◽  
Hydrophobic Solutes ◽  
The Magnetic Field ◽  
Density Of Water ◽  
Induced Adsorption

The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

scholarly journals Comparison of the measured and modelled electron densities and temperatures in the ionosphere and plasmasphere during 20-30 January, 1993

2000 ◽  
Vol 18 (10) ◽  
pp. 1257-1262 ◽  
Author(s):  
A. V. Pavlov ◽  
T. Abe ◽  
K.-I. Oyama
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Electron Temperature ◽  
Field Line ◽  
Electron Density ◽  
Magnetic Field Line ◽  
New Approach ◽  
Additional Heating ◽  
Vibrational Levels ◽  
The Magnetic Field

Abstract. We present a comparison of the electron density and temperature behaviour in the ionosphere and plasmasphere measured by the Millstone Hill incoherent-scatter radar and the instruments on board of the EXOS-D satellite with numerical model calculations from a time-dependent mathematical model of the Earth's ionosphere and plasmasphere during the geomagnetically quiet and storm period on 20–30 January, 1993. We have evaluated the value of the additional heating rate that should be added to the normal photoelectron heating in the electron energy equation in the daytime plasmasphere region above 5000 km along the magnetic field line to explain the high electron temperature measured by the instruments on board of the EXOS-D satellite within the Millstone Hill magnetic field flux tube in the Northern Hemisphere. The additional heating brings the measured and modelled electron temperatures into agreement in the plasmasphere and into very large disagreement in the ionosphere if the classical electron heat flux along magnetic field line is used in the model. A new approach, based on a new effective electron thermal conductivity coefficient along the magnetic field line, is presented to model the electron temperature in the ionosphere and plasmasphere. This new approach leads to a heat flux which is less than that given by the classical Spitzer-Harm theory. The evaluated additional heating of electrons in the plasmasphere and the decrease of the thermal conductivity in the topside ionosphere and the greater part of the plasmasphere found for the first time here allow the model to accurately reproduce the electron temperatures observed by the instruments on board the EXOS-D satellite in the plasmasphere and the Millstone Hill incoherent-scatter radar in the ionosphere. The effects of the daytime additional plasmaspheric heating of electrons on the electron temperature and density are small at the F-region altitudes if the modified electron heat flux is used. The deviations from the Boltzmann distribution for the first five vibrational levels of N2(v) and O2(v) were calculated. The present study suggests that these deviations are not significant at the first vibrational levels of N2 and O2 and the second level of O2, and the calculated distributions of N2(v) and O2(v) are highly non-Boltzmann at vibrational levels v > 2. The resulting effect of N2(v > 0) and O2(v > 0) on NmF2 is the decrease of the calculated daytime NmF2 up to a factor of 1.5. The modelled electron temperature is very sensitive to the electron density, and this decrease in electron density results in the increase of the calculated daytime electron temperature up to about 580 K at the F2 peak altitude giving closer agreement between the measured and modelled electron temperatures. Both the daytime and night-time densities are not reproduced by the model without N2(v > 0) and O2(v > 0), and inclusion of vibrationally excited N2 and O2 brings the model and data into better agreement.Key words: Ionosphere (ionospheric disturbances; ionosphere-magnetosphere interactions; plasma temperature and density)  

Doppler-Shifted Cyclotron Resonance in Thin Metal Films

1972 ◽  
Vol 50 (18) ◽  
pp. 2122-2137
Author(s):  
R. Turner ◽  
J. F. Cochran
Keyword(s):  
Magnetic Field ◽  
Metal Films ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Free Electrons ◽  
Fermi Surfaces ◽  
First Order ◽  
Simple Quantum ◽  
The Magnetic Field ◽  
Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

scholarly journals Experimental and numerical investigation of plasma parameters in the magnetosheath

2018 ◽  
Vol 145 ◽  
pp. 03003
Author(s):  
Polya Dobreva ◽  
Monio Kartalev ◽  
Olga Nitcheva ◽  
Natalia Borodkova ◽  
Georgy Zastenker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Numerical Investigation ◽  
Euler Equations ◽  
Ideal Gas ◽  
Bow Shock ◽  
Plasma Parameters ◽  
Wind Spacecraft ◽  
The Magnetic Field ◽  
Good Agreement

We investigate the behaviour of the plasma parameters in the magnetosheath in a case when Interball-1 satellite stayed in the magnetosheath, crossing the tail magnetopause. In our analysis we apply the numerical magnetosheath-magnetosphere model as a theoretical tool. The bow shock and the magnetopause are self-consistently determined in the process of the solution. The flow in the magnetosheath is governed by the Euler equations of compressible ideal gas. The magnetic field in the magnetosphere is calculated by a variant of the Tsyganenko model, modified to account for an asymmetric magnetopause. Also, the magnetopause currents in Tsyganenko model are replaced by numericaly calulated ones. Measurements from WIND spacecraft are used as a solar wind monitor. The results demonstrate a good agreement between the model-calculated and measured values of the parameters under investigation.

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