Kelvin–Helmholtz Instability and Cooling Limitations of a Vertical Molten Sheet Confined by Alternating Magnetic Fields

1989 ◽  
Vol 111 (2) ◽  
pp. 352-356 ◽  
Author(s):  
J. R. Hull
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Magnetic Fields ◽  
Physical Properties ◽  
Cooling Rate ◽  
Maximum Velocity ◽  
Flow Channel ◽  
Helmholtz Instability ◽  
Channel Geometry ◽  
Alternating Magnetic Fields

Limitations imposed by a Kelvin–Helmholtz-type instability on the cooling of a vertical molten sheet that is confined by magnetic fields alternating in time are calculated. The molten sheet is cooled by a gas stream flowing on both sides of the sheet. The Kelvin–Helmholtz instability imposes a maximum velocity on the cooling gas, which limits the cooling rate. The maximum cooling rate is calculated with respect to the maximum velocity, gas physical properties, flow channel geometry, surface tension, and magnetic field properties.

scholarly journals Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

2013 ◽  
Vol 31 (9) ◽  
pp. 1535-1541 ◽  
Author(s):  
K.-I. Nishikawa ◽  
P. Hardee ◽  
B. Zhang ◽  
I. Duţan ◽  
M. Medvedev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Magnetic Fields ◽  
Electric Field ◽  
Flow Direction ◽  
Transverse Magnetic ◽  
Velocity Shear ◽  
Helmholtz Instability ◽  
Magnetic Field Generation ◽  
Relativistic Jet

Abstract. We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin–Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5) is larger than for a relativistic jet case (γj = 15).

scholarly journals Effect of moderate magnetic fields on the surface tension of aqueous liquids: a reliable assessment

RSC Advances ◽  
2019 ◽  
Vol 9 (18) ◽  
pp. 10030-10033 ◽  
Author(s):  
Masayuki Hayakawa ◽  
Jacopo Vialetto ◽  
Manos Anyfantakis ◽  
Masahiro Takinoue ◽  
Sergii Rudiuk ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Magnetic Fields ◽  
Reliable Assessment

A novel setup measures the effect of magnetic field intensities on the surface tension of liquids placed inside uniform fields.

scholarly journals The loss of energy in metal plates of finite thickness, due to eddy currents produced by alternating magnetic fields

1926 ◽  
Vol 111 (759) ◽  
pp. 604-614 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Eddy Currents ◽  
Finite Thickness ◽  
Metal Plate ◽  
The Self ◽  
Alternating Magnetic Field ◽  
Metal Plates ◽  
Alternating Magnetic Fields

The induction of eddy currents in metal plates which are subjected to alternating magnetic fields has been discussed by Clerk-Maxwell, J. J. Thomson and many others. When an alternating magnetic field is produced normal to the surface of a metal plate, eddy currents are induced at the surface of the plate, which gradually penetrate its interior, the current dying away as it penetrates more deeply into the metal. The diffusion of the currents into the plate depends upon the self-induction and resistance of the paths along which they flow, and can be calculated by the same kind of formula as is used for determining the conduction of heat through a metal slab.

Effect of Weak Magnetic Field on the Structure and Physical Properties of Chitosan Membranes

2021 ◽  
Vol 1044 ◽  
pp. 181-189
Author(s):  
Ni Nyoman Rupiasih ◽  
Made Sumadiyasa ◽  
I Ketut Putra ◽  
Ida Ayu Putu Inten Gayatri
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Physical Properties ◽  
Tensile Modulus ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Weak Magnetic Fields ◽  
Chitosan Membranes ◽  
Uptake Test

The purpose of this study was to evaluate the effect of weak magnetic fields on the structure and physical properties of chitosan (Ch) membranes. The membranes were prepared by a casting method using chitosan and a solvent of acetic acid. The magnetic field of 1.5 mT is applied during the membrane-forming reaction with administration times of 2, 4, 8, and 12 hours. The membranes formed were named M-2h, M-4h, M-8h, and M-12h, respectively. The chitosan membrane without magnetic fields is used as a control, namely M-0. The structure and physical properties of the membranes were examined using Fourier Transform Infra-Red (FTIR) spectrophotometer, water uptake test, dynamic mechanical analysis (DMA), and X-ray diffraction (XRD). The result showed that the membranes with magnetic fields are thicker compared to the control membrane. FTIR analysis revealed that some peaks of the membranes with magnetic fields shifted to the higher or lower wavenumber with increased or decreased absorption intensity. The membranes become stronger and more flexible; their degree of crystallinity increases as increasing the time of the magnetic fields' application, and their hydrophilicity improved. The membranes' crystal structure becomes more regular, and their degree of crystallinity increases as increasing the time of the application of the magnetic fields; and their mechanical properties such as ultimate tensile strength, tensile modulus, and elongation at break were improved. Those results explain that the structure and physical properties of chitosan membranes were significantly affected by the membrane-forming reaction's magnetic fields.

Control of the Alloying Element Distribution in Al-Alloys by High Magnetic Fields

2007 ◽  
Vol 539-543 ◽  
pp. 457-462 ◽  
Author(s):  
Qiang Wang ◽  
Xue Jun Pang ◽  
Chun Jiang Wang ◽  
Tie Liu ◽  
Dong Gang Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Physical Properties ◽  
High Magnetic Field ◽  
Element Distribution ◽  
Field Conditions ◽  
High Magnetic Fields ◽  
Gradient Magnetic Field ◽  
The Matrix ◽  
Al Mg Alloys

The distribution and solidified structure of alloying elements are important for the quality and the properties of alloys. In the present study, the solidification behavior of aluminum-rich alloys is studied under various high magnetic field conditions, and the influences of uniform and gradient magnetic fields with different intensity and direction on the distribution and the morphology of solute elements of Al-Cu and Al-Mg alloys are investigated. It is found that because of the differences of the electromagnetic force (Lorentz and magnetization forces) acting on Cu element and Mg element with different physical properties in the matrix, the regularities of distribution for Cu element and Mg element are opposite just in the intracrystalline and intergranular under high uniform magnetic field condition, and not only the content but the distributions of Cu and Mg elements are obviously different under high gradient magnetic field conditions as well. It can be concluded that high magnetic field has different effect on the solute distribution in alloys with different physical properties such as density, susceptibility, conductivity, etc. And the experimental results indicate that it is possible to control the terminal solubility and morphology of the solute elements in alloys by high magnetic fields.

Flow Control Using Alternating Magnetic Fields During Crystal Growth From a Melt

2012 ◽  
Author(s):  
Yue Huang ◽  
Kenneth E. Davis ◽  
Brent C. Houchens
Keyword(s):  
Magnetic Field ◽  
Crystal Growth ◽  
Magnetic Fields ◽  
Flow Control ◽  
Body Force ◽  
Stokes Equations ◽  
Magnetic Reynolds Number ◽  
Rotating Magnetic Field ◽  
Bandgap Energy ◽  
Alternating Magnetic Fields

Flow control during bulk melt crystal growth is desirable for producing ternary alloy semiconductors with tunable lattice parameters and bandgap energy, providing custom materials for specific electro-optical applications. Segregation between constituent elements in the melt, be it through preferential rejection at the growth front or density variations, limits the growth rate and the uniformity in the crystal. External alternating magnetic fields are employed to stir the electrically conducting melt. While mixing is desired, turbulent flow is generally not. Precise control is required to maintain a laminar melt flow while providing sufficient mixing. Stirring via a rotating magnetic field (RMF) and a three-coil traveling magnetic field (TMF) is modeled and compared for a cylindrical melt confined in an ampule. The RMF imposes a body force in the azimuthal direction while the TMF induces primarily radial and axial body forces. The magnetic fields are effectively decoupled from the flow fields due to the small magnetic Reynolds number. Therefore, the magnetic fields are first determined using a finite element solver. The flows are then solved by a spectral element model of the Navier-Stokes equations including an electromagnetic body force term.

scholarly journals The Fine-Tuned Release of Antioxidant from Superparamagnetic Nanocarriers under the Combination of Stationary and Alternating Magnetic Fields

Antioxidants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1212
Author(s):  
Lucija Mandić ◽  
Anja Sadžak ◽  
Ina Erceg ◽  
Goran Baranović ◽  
Suzana Šegota
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Quantum Interference ◽  
Fine Tuning ◽  
Force Microscopy ◽  
Peg 4000 ◽  
Vis Spectroscopy ◽  
Poly Ethylene ◽  
Alternating Magnetic Fields

Superparamagnetic magnetite nanoparticles (MNPs) with excellent biocompatibility and negligible toxicity were prepared by solvothermal method and stabilized by widely used and biocompatible polymer poly(ethylene glycol) PEG-4000 Da. The unique properties of the synthesized MNPs enable them to host the unstable and water-insoluble quercetin as well as deliver and localize quercetin directly to the desired site. The chemical and physical properties were validated by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE–SEM), atomic force microscopy (AFM), superconducting quantum interference device (SQUID) magnetometer, FTIR spectroscopy and dynamic light scattering (DLS). The kinetics of in vitro quercetin release from MNPs followed by UV/VIS spectroscopy was controlled by employing combined stationary and alternating magnetic fields. The obtained results have shown an increased response of quercetin from superparamagnetic MNPs under a lower stationary magnetic field and s higher frequency of alternating magnetic field. The achieved findings suggested that we designed promising targeted quercetin delivery with fine-tuning drug release from magnetic MNPs.

scholarly journals The Effect of Water Magnetized with Negative Magnetic Field on Effectiveness of Selected Zoocides in the Control of Two-Spotted Spider Mite (Tetranychus Urticae Koch)

2009 ◽  
Vol 49 (1) ◽  
pp. 87-92
Author(s):  
Romuald Górski ◽  
Marek Wachowiak ◽  
Michał Tomczak
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Physical Properties ◽  
Tetranychus Urticae ◽  
Spider Mite ◽  
Effect Of Water ◽  
Fe Content ◽  
Simultaneous Use ◽  
Two Spotted Spider Mite ◽  
Tetranychus Urticae Koch

The Effect of Water Magnetized with Negative Magnetic Field on Effectiveness of Selected Zoocides in the Control of Two-Spotted Spider Mite (Tetranychus UrticaeKoch)The results of experiments showed an effect of negative magnetic field on some chemical and physical properties of water. A slight increase in iron (Fe) content, a decrease in zinc (Zn) level and an increase in surface tension (Dc) were observed in the study. At the same time the effect of magnetically modified water on an increase in effectiveness of tested zoocides was observed in the control of the two-spotted spider mite (Tetranychus urticaeKoch). A strong and statistically significant increase in the effectiveness of zoocide Talstar 100 EC was recorded after the application of one and three magnetizers, preparation Omite 30 WP after the application of two magnetizers, acaricide Magus 200 SC after the application of one and two magnetizers as well as a simultaneous use of one magnetizer and two semi-rings. Acaricide Ortus 05 SC showed a marked increase in the effectiveness in all treatments with the use of magnetically modified water.

Proton NMR Investigations of the Smectic-C Phases of Three Alkyloxy-Azoxybenzenes

1983 ◽  
Vol 38 (4) ◽  
pp. 434-446 ◽  
Author(s):  
St. Limmer ◽  
M. Findeisen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cooling Rate ◽  
Strong Magnetic Field ◽  
Proton Nmr ◽  
The Other ◽  
Magnetic Field Direction ◽  
Slow Cooling ◽  
Smectic C ◽  
Second Moments

Proton NMR investigations of the smectic-C phases of three 4,4′-bis-n-alkyloxy-azoxybenzenes (C7, C8 , C9) with temperature independent tilt angles are presented.The behaviour of well-aligned samples (strong magnetic field ≳ 1.5 T, slow cooling rate) under rotation in the field can be described by the models of Luz and Meiboom, and Wise, Smith, and Doane, (LM/WSD), resp. However, on polarization of the samples in presence of magnetic fields ≲ 0.75 T the molecular directors are not arranged preferentially parallel to the direction of the polarizing magnetic field but are rather inclined, i.e., the layers are stacked preferentially perpendicular to the original magnetic field direction (PSL model). It is shown that all the angular dependences of NMR second moments can be interpreted in terms of a superposition of the LM/WSD and PSL models, or, on the other hand, by assuming totally disordered fractions of the samples together with portions that fully obey the behaviour demanded by one of the above models (LM/WSD or PSL). The tilt angles derived from the comparison of experimental and theoretical angular dependences of the second moments for well-aligned samples are applied to the explanation of the experiments at lower polarizing fields successfully, too.

Sign in / Sign up

Export Citation Format

Share Document