Thermocapillary Instability With a Rotating Magnetic Field and System Rotation

2003 ◽  
Author(s):  
Nancy Ma ◽  
John S. Walker ◽  
Laurent Martin Witkowski
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Free Surface ◽  
Stability Analysis ◽  
Angular Velocity ◽  
Thermocapillary Convection ◽  
Rotating Magnetic Field ◽  
Azimuthal Direction ◽  
Critical Mode ◽  
Thermocapillary Instability

This paper presents a linear stability analysis for the thermocapillary convection in a liquid bridge bounded by two planar liquid-solid interfaces at the same temperature and by a cylindrical free surface with an axisymmetric heat input. The two solid boundaries are rotated at the same angular velocity in one azimuthal direction, and a rotating magnetic field is applied in the opposite azimuthal direction. The critical values of the Reynolds number for the thermocapillary convection and the critical-mode frequencies are presented as functions of the magnetic Taylor number for the rotating magnetic field and of the Reynolds number for the angular velocity of the solid boundaries.

Combined Effects of Rotating Magnetic Field and Rotating System on the Thermocapillary Instability in the Floating Zone Crystal Growth Process

2004 ◽  
Vol 126 (2) ◽  
pp. 230-235 ◽  
Author(s):  
Nancy Ma ◽  
John S. Walker ◽  
Laurent Martin Witkowski
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Angular Velocity ◽  
Thermocapillary Convection ◽  
Rotating Magnetic Field ◽  
Azimuthal Direction ◽  
Rotating System ◽  
Critical Mode ◽  
Crystal Growth Process ◽  
Thermocapillary Instability

This paper presents a linear stability analysis for the thermocapillary convection in a liquid bridge bounded by two planar liquid-solid interfaces at the same temperature and by a cylindrical free surface with an axisymmetric heat input. The two solid boundaries are rotated at the same angular velocity in one azimuthal direction, and a rotating magnetic field is applied in the opposite azimuthal direction. The critical values of the Reynolds number for the thermocapillary convection and the critical-mode frequencies are presented as functions of the magnetic Taylor number for the rotating magnetic field and of the Reynolds number for the angular velocity of the solid boundaries.

scholarly journals The effect of uniform magnetic field on spatial-temporal evolution of thermocapillary convection with the silicon oil based ferrofluid

2020 ◽  
Vol 24 (6 Part B) ◽  
pp. 4159-4171
Author(s):  
Shuo Yang ◽  
Rui Ma ◽  
Qiaosheng Deng ◽  
Guofeng Wang ◽  
Yu Gao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Transverse Magnetic Field ◽  
Liquid Bridge ◽  
Thermocapillary Convection ◽  
Surface Deformation ◽  
Axial Magnetic Field ◽  
Transverse Magnetic ◽  
Surface Flow ◽  
Silicon Oil

A uniform axial or transverse magnetic field is applied on the silicon oil based ferrofluid of high Prandtl number fluid (Pr ? 111.67), and the effect of magnetic field on the thermocapillary convection is investigated. It is shown that the location of vortex core of thermocapillary convection is mainly near the free surface of liquid bridge due to the inhibition of the axial magnetic field. A velocity stagnation region is formed inside the liquid bridge under the axial magnetic field (B = 0.3-0.5 T). The disturbance of bulk reflux and surface flow is suppressed by the increasing axial magnetic field. There is a dynamic response of free surface deformation to the axial magnetic field, and then the contact angle variation of the free surface at the hot corner is as following, ?hot, B = 0.5 T = 83.34? > ?hot, B = 0.3 T = 72.16? > > ?hot,B = 0.1 T = 54.21? > ?hot, B = 0 T = 43.33?. The results show that temperature distribution near the free surface is less and less affected by thermocapillary convection with the increasing magnetic field, and it presents a characteristic of heat-conduction. In addition, the transverse magnetic field does not realize the fundamental inhibition for thermocapillary convection, but it transfers the influence of thermocapillary convection to the free surface.

scholarly journals Investigation of mixing time in liquid under influence of rotating magnetic field

2017 ◽  
Vol 38 (4) ◽  
pp. 555-565
Author(s):  
Alicja Przybył ◽  
Rafał Rakoczy ◽  
Maciej Konopacki ◽  
Marian Kordas ◽  
Radosław Drozd ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Mixing Time ◽  
Rotating Magnetic Field ◽  
Homogenization Time ◽  
Set Up ◽  
The Relationship ◽  
The Magnetic Field

Abstract The aim of the study was to present an experimental investigation of the influence of the RMF on mixing time. The obtained results suggest that the homogenization time for the tested experimental set-up depending on the frequency of the RMF can be worked out by means of the relationship between the dimensionless mixing time number and the Reynolds number. It was shown that the magnetic field can be applied successfully to mixing liquids.

Dynamic and Stability Analysis of the Rotating Nanobeam in a Nonuniform Magnetic Field Considering the Surface Energy

2016 ◽  
Vol 08 (04) ◽  
pp. 1650048 ◽  
Author(s):  
M. Baghani ◽  
M. Mohammadi ◽  
A. Farajpour
Keyword(s):  
Magnetic Field ◽  
Stability Analysis ◽  
Angular Velocity ◽  
Surface Energy ◽  
Axial Load ◽  
Nonuniform Magnetic Field ◽  
Small Scale ◽  
Stability Behavior ◽  
Compressive Axial Load ◽  
The Stability

It is well-known that rotating nanobeams can have different dynamic and stability responses to various types of loadings. In this research, attention is focused on studying the effects of magnetic field, surface energy and compressive axial load on the dynamic and the stability behavior of the nanobeam. For this purpose, it is assumed that the rotating nanobeam is located in the nonuniform magnetic field and subjected to compressive axial load. The nonlocal elasticity theory and the Gurtin–Murdoch model are applied to consider the effects of inter atomic forces and surface energy effect on the vibration behavior of rotating nanobeam. The vibration frequencies and critical buckling loads of the nanobeam are computed by the differential quadrature method (DQM). Then, the numerical results are testified with those results are presented in the published works and a good correlation is obtained. Finally, the effects of angular velocity, magnetic field, boundary conditions, compressive axial load, small scale parameter and surface elastic constants on the dynamic and the stability behavior of the nanobeam are studied. The results show that the magnetic field, surface energy and the angular velocity have important roles in the dynamic and stability analysis of the nanobeams.

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.

scholarly journals Linear stability of thermocapillary convection in cylindrical liquid bridges under axial magnetic fields

1999 ◽  
Vol 394 ◽  
pp. 281-302 ◽  
Author(s):  
M. PRANGE ◽  
M. WANSCHURA ◽  
H. C. KUHLMANN ◽  
H. J. RATH
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Magnetic Fields ◽  
Prandtl Number ◽  
Linear Stability ◽  
Thermocapillary Convection ◽  
Axial Magnetic Field ◽  
Unstable Mode ◽  
Linear Stability Theory ◽  
The Stability

The stability of axisymmetric steady thermocapillary convection of electrically conducting fluids in half-zones under the influence of a static axial magnetic field is investigated numerically by linear stability theory. In addition, the energy transfer between the basic state and a disturbance is considered in order to elucidate the mechanics of the most unstable mode. Axial magnetic fields cause a concentration of the thermocapillary flow near the free surface of the liquid bridge. For the low Prandtl number fluids considered, the most dangerous disturbance is a non-axisymmetric steady mode. It is found that axial magnetic fields act to stabilize the basic state. The stabilizing effect increases with the Prandtl number and decreases with the zone height, the heat transfer rate at the free surface and buoyancy when the heating is from below. The magnetic field also influences the azimuthal symmetry of the most unstable mode.

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