Liquid-Metal MHD Open-Channel Flows

1984 ◽  
Vol 51 (1) ◽  
pp. 13-18 ◽  
Author(s):  
P. R. Hays ◽  
J. S. Walker
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Magnetic Fields ◽  
Liquid Metal ◽  
Boundary Layers ◽  
Open Channel ◽  
Three Dimensional ◽  
Viscous Effects ◽  
Channel Bottom ◽  
Dimensional Variable

Many metallurgical applications of magnetohydrodynamics (MHD) involve open-channel liquid-metal flows with magnetic fields. This paper treats the three-dimensional, variable-depth flow in a rectangular open channel having an electrically insulating bottom and perfectly conducting sides. A steady, uniform magnetic field is applied perpendicular to the channel bottom. Induced magnetic fields and surface tension effects are neglected, while the applied magnetic field is sufficiently strong that inertial effects are negligible everywhere. Viscous effects are confined to boundary layers adjacent to the bottom, sides, and free surface. Solutions are presented for the inviscid core and the boundary layers. The locations of the free surface above the core and above the boundary layers adjacent to the sides are obtained. The side-layer variables are rescaled into universal profile functions which depend on the coordinates in the channel’s cross section and on a parameter related to the local slopes of the bottom and the free surface. The solutions for the side layers in open channels are compared to the side-layer solutions for certain rectangular closed ducts in order to reveal the effects of the free surface. This comparison leads to a qualitative correspondence principle between open-channel and closed-duct side-layer solutions. The similarities and differences between corresponding open-channel and closed-duct side layers are discussed.

Thermocapillary convection in a cylindrical liquid-metal floating zone with a strong axial magnetic field and with a non-axisymmetric heat flux

1997 ◽  
Vol 345 ◽  
pp. 31-43 ◽  
Author(s):  
T. E. MORTHLAND ◽  
J. S. WALKER
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Free Surface ◽  
Liquid Metal ◽  
Thermocapillary Convection ◽  
Axial Magnetic Field ◽  
Hot Spot ◽  
Cold Spot ◽  
Floating Zone ◽  
Viscous Effects

This paper treats the steady three-dimensional thermocapillary convection in a cylindrical liquid-metal zone between the isothermal ends of two coaxial solid cylinders and surrounded by an atmosphere. There is a uniform steady magnetic field which is parallel to the common centrelines of the liquid zone and solid cylinders, and there is a non-axisymmetric heat flux into the liquid's free surface. The magnetic field is sufficiently strong that inertial effects and convective heat transfer are negligible, and that viscous effects are confined to thin boundary layers adjacent to the free surface and to the liquid–solid interfaces. With an axisymmetric heat flux, the axisymmetric thermocapillary convection is confined to the thin layer adjacent to the free surface, but with a non-axisymmetric heat flux, there is an azimuthal flow inside the free-surface layer from the hot spot to the cold spot with the circulation completed by flow across the inviscid central core region. This problem is related to the magnetic damping of thermocapillary convection for the floating-zone growth of semiconductor crystals in Space.

Numerical simulation of liquid-metal MHD flows in rectangular ducts

1990 ◽  
Vol 216 ◽  
pp. 161-191 ◽  
Author(s):  
A. Sterl
Keyword(s):  
Magnetic Field ◽  
Liquid Metal ◽  
Boundary Layers ◽  
Hartmann Number ◽  
Three Dimensional ◽  
Mhd Flow ◽  
Two Dimensional ◽  
Square Duct ◽  
Mhd Flows ◽  
Pressure Losses

To design self-cooled liquid metal blankets for fusion reactors, one must know about the behaviour of MHD flows at high Hartmann numbers. In this work, finite difference codes are used to investigate the influence of Hartmann number M, interaction parameter N, wall conductance ratio c, and changing magnetic field, respectively, on the flow.As liquid-metal MHD flows are characterized by thin boundary layers, resolution of these layers is the limiting issue. Hartmann numbers up to 103 are reached in the two-dimensional case of fully developed flow, while in three-dimensional flows the limit is 102. However, the calculations reveal the main features of MHD flows at large M. They are governed by electric currents induced in the fluid. Knowing the paths of these currents makes it possible to predict the flow structure.Results are shown for two-dimensional flows in a square duct at different Hartmann numbers and wall conductivities. While the Hartmann number governs the thickness of the boundary layers, the wall conductivities are responsible for the pressure losses and the structure of the flows. The most distinct feature is the side layers where the velocities can exceed those at the centre by orders of magnitude.The three-dimensional results are also for a square duct. The main interest here is to investigate the redistribution of the fluid in a region where the magnetic field changes. Large axial currents are induced leading to the ‘M-shaped’ velocity profiles characteristic of MHD flow. So-called Flow Channel Inserts (FCI), of great interest in blanket design, are investigated. They serve to decouple the load carrying wall from the currents in the fluid. The calculations show that the FCI is indeed a suitable measure to reduce the pressure losses in the blanket.

Liquid-metal flow in an insulated rectangular expansion with a strong transverse magnetic field

1995 ◽  
Vol 305 ◽  
pp. 111-126 ◽  
Author(s):  
John S. Walker ◽  
Basil F. Picologlou
Keyword(s):  
Magnetic Field ◽  
Liquid Metal ◽  
Boundary Layers ◽  
Applied Magnetic Field ◽  
Metal Flow ◽  
Three Dimensional ◽  
Liquid Metal Flow ◽  
Constant Area ◽  
Large Expansion ◽  
The Magnetic Field

This paper concerns a steady liquid-metal flow through an expansion or contraction with electrically insulated walls, with rectangular cross-sections and with a uniform, transverse, externally applied magnetic field. One pair of duct walls is parallel to the applied magnetic field, and the other pair diverges or converges symmetrically about a plane which is perpendicular to the field. The magnetic field is assumed to be sufficiently strong that inertial effects can be neglected and that the well-known Hartmann-layer solution is valid for the boundary layers on the walls which are not parallel to the magnetic field. A general treatment of three-dimensional flows in constant-area ducts is presented. An error in the solution of Walker et al. (1972) is corrected. A smooth expansion between two different constant-area ducts is treated. In the expansion the flow is concentrated inside the boundary layers on the sides which are parallel to the magnetic field, while the flow at the centre of the duct is very small and may be negative for a large expansion slope. In each constant-area duct, the flow evolves from a concentration near the sides at the junction with the expansion to the appropriate fully developed flow far upstream or downstream of the expansion. The pressure drop associated with the three-dimensional flow increases as the slope. increases.

scholarly journals Magnetic and Electronic Properties of π-d Interacting Molecular Magnetic Superconductor κ-(BETS)2FeX4 (X = Cl, Br) Studied by Angle-Resolved Heat Capacity Measurements

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 66 ◽  
Author(s):  
Shuhei Fukuoka ◽  
Sotarou Fukuchi ◽  
Hiroki Akutsu ◽  
Atsushi Kawamoto ◽  
Yasuhiro Nakazawa
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Magnetic Fields ◽  
Temperature Dependence ◽  
Three Dimensional ◽  
Magnetic Interaction ◽  
Spin Configuration ◽  
Magnetic Superconductor ◽  
Heat Capacity Measurements ◽  
Long Range Ordering

Thermodynamic picture induced by π-d interaction in a molecular magnetic superconductor κ-(BETS)2FeX4 (X = Cl, Br), where BETS is bis(ethylenedithio)tetraselenafulvalene, studied by single crystal calorimetry is reviewed. Although the S = 5/2 spins of Fe3+ in the anion layers form a three-dimensional long-range ordering with nearly full entropy of Rln6, a broad hump structure appears in the temperature dependence of the magnetic heat capacity only when the magnetic field is applied parallel to the a axis, which is considered as the magnetic easy axis. The scaling of the temperature dependence of the magnetic heat capacity of the two salts is possible using the parameter of |Jdd|/kB and therefore the origin of the hump structure is related to the direct magnetic interaction, Jdd, that is dominant in the system. Quite unusual crossover from a three-dimensional ordering to a one-dimensional magnet occurs when magnetic fields are applied parallel to the a axis. A notable anisotropic field-direction dependence against the in-plane magnetic field was also observed in the transition temperature of the bulk superconductivity by the angle-resolved heat capacity measurements. We discuss the origin of this in-plane anisotropy in terms of the 3d electron spin configuration change induced by magnetic fields.

Room Temperature Sample Scanning SQUID Microscope for Imaging the Magnetic Fields of Geological Specimens

2013 ◽  
Vol 475-476 ◽  
pp. 3-6 ◽  
Author(s):  
Qing Meng Wang ◽  
Hua Feng Qin ◽  
Qing Song Liu ◽  
Tao Song
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Magnetic Fields ◽  
Liquid Helium ◽  
Quantum Interference ◽  
Three Dimensional ◽  
Input Circuit ◽  
Pickup Coil ◽  
Weak Magnetic Fields ◽  
Scanning Squid

A microscope to image weak magnetic fields using a low-temperature superconducting quantum interference device (SQUID) had developed with a liquid helium consumption rate of ~0.5L/hour. The gradient pickup coil is made by a low-temperature superconducting niobium wire with a diameter of 66 μm, which is coupled to the input circuit of the SQUID and is then enwound on the sapphire bobbin. Both of the pickup coil and the SQUID sensor are installed in a red copper cold finger, which is thermally anchored to the liquid helium evaporation platform in the vacuum space of the cryostat. To reduce the distance between the pickup coil and sample, a 100 μm thick sapphire window is nestled up to the bottom of the cryostat. A three-dimensional scanning stage platform with a 50 cm Teflon sample rack under the sapphire window had the precision of 10 μm. To test the fidelity of the new facility, the distribution of the magnetic field of basalt slice specimens was determined. Results show that the spatial resolution of the newly-designed facility is 500 μm with a gradient magnetic field sensitivity of 380fT. This opens new opportunities in examining the distribution of magnetic assemblages in samples, which bear great geological and geophysical information.

Large Eddy Simulations of Taylor-Go¨rtler Instabilities in Transitional and Turbulent Boundary Layers

2010 ◽  
Author(s):  
Sergej Gordeev ◽  
Robert Stieglitz ◽  
Volker Heinzel
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Liquid Metal ◽  
Boundary Layers ◽  
High Power ◽  
Turbulent Boundary Layers ◽  
Numerical Predictions ◽  
Back Plate ◽  
Exit Nozzle ◽  
Large Eddy

Free surface liquid metal targets are considered in several high power targets as a tool to produce secondary particles, since their power density exceeds material sustainable limits. Many target designs consider due to the high power deposited in the liquid a concave formed back plate in order to yield a higher boiling point. Upstream the free surface target domain the liquid metal flow is conditioned by a nozzle. However, a back-wall curvature as well as a concave shaped exit nozzle contour can lead to the occurrence of secondary motions in the flow caused by Taylor-Go¨rtler (TG) instabilities. These motions may impact the hydrodynamic stability the flow and also lead to an undesired heat transfer from the hottest region produced within the liquid target towards the uncooled back plate. In this study, the suitability of the Large Eddy Simulation (LES) technique to simulate the formation, development and destruction TG instabilities in transitional and turbulent boundary layers was tested by comparing the simulation results with experimental data reported in literature. All comparisons exhibit a qualitative and quantitative good agreement between experimental data and numerical predictions regarding the mean flow parameters and unsteady large-scale structures caused by TG instabilities.

Effects of magnetic field orientation on a liquid‐metal free surface in a sliding electrical contact

1992 ◽  
Vol 71 (8) ◽  
pp. 3713-3720 ◽  
Author(s):  
J. S. Walker ◽  
D. M. Audet ◽  
G. Talmage ◽  
S. H. Brown ◽  
N. A. Sondergaard
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Liquid Metal ◽  
Electrical Contact ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Metal Free ◽  
Sliding Electrical Contact
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