Abstract
Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.
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Abbreviations
- B 0 :
-
magnitude of magnetic induction
- Br, Bθ :
-
radial and azimuthal magnetic induction components
- C :
-
wall admittance
- d :
-
cell diameter
- d w :
-
wall thickness
- g :
-
gravity at earth's surface
- Ha :
-
Hartmann number
- h :
-
cell height
- k f :
-
thermal conductivity of fluid
- k w :
-
thermal conductivity of wall
- L1, L2, L3, L4:
-
thermistor temperatures
- Ra :
-
Rayleigh number
- Ra c :
-
critical Rayleigh number for the transition from no flow to laminar flow
- Ra t :
-
critical Rayleigh number for the transition from time-independent to time-dependent flow
- r :
-
radial coordinate
- T a :
-
temperature at top of cell
- T b :
-
temperature at bottom of cell
- Δ T:
-
temperature difference between cell bottom and cell top
- ΔTc :
-
critical temperature difference between cell bottom and top time
- t :
-
time
- U1, U2, U3, U4:
-
thermistor temperatures
- z :
-
vertical coordinate
- α:
-
volumetric thermal expansion coefficient
- δ:
-
skin depth
- k :
-
thermal diffusivity
- μ:
-
magnetic permeability
- ν:
-
kinematic viscosity
- ρ:
-
density
- σ:
-
electrical conductivity
- θ:
-
azimuthal coordinate
- ω:
-
angular frequency of magnetic induction
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This work was supported by the Microgravity Science and Applications Division of the National Aeronautics and Space Administration.
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Volz, M.P., Mazuruk, K. Flow transitions in a rotating magnetic field. Experiments in Fluids 20, 454–459 (1996). https://doi.org/10.1007/BF00189385
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DOI: https://doi.org/10.1007/BF00189385