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Spin-up flow of ferrofluids: Asymptotic theory and experimental measurements
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10.1063/1.2907221
/content/aip/journal/pof2/20/5/10.1063/1.2907221
http://aip.metastore.ingenta.com/content/aip/journal/pof2/20/5/10.1063/1.2907221

Figures

Image of FIG. 1.
FIG. 1.

Schematic illustration of the coupled ferrohydrodynamic problem for spin-up flow. The azimuthal velocity component and axially directed spin velocity are obtained for a long column of ferrofluid of external radius subjected to a uniform rotating magnetic field perpendicular to the axis of the cylinder. The magnetic field source is modeled as a -directed surface current distribution , which is backed by a material of infinite magnetic permeability, .

Image of FIG. 2.
FIG. 2.

Torque measurements as a function of frequency and amplitude of the applied magnetic field for EMG705̱0 using a spindle volume of .

Image of FIG. 3.
FIG. 3.

Experimental velocity profiles for EMG705̱0 and EMG900̱2 ferrofluids. Ultrasonic transducers were placed at half the height of the container. Angles are with respect to the diagonal.

Image of FIG. 4.
FIG. 4.

Velocity profiles for (a) EMG705̱0 and (b) EMG900̱2 ferrofluids showing the dependence of flow with frequency for an applied magnetic field of amplitude rms.

Image of FIG. 5.
FIG. 5.

Velocity profiles for (a) EMG705̱0 and (b) EMG900̱2 ferrofluids, showing the dependence of flow with amplitude of the applied magnetic field for a frequency of .

Image of FIG. 6.
FIG. 6.

Velocity profile for (a) EMG705̱0 and (b) EMG900̱2 ferrofluids using probes placed at four different heights of the container with cover.

Image of FIG. 7.
FIG. 7.

Axial velocity component measured for (a) EMG705̱0 and (b) EMG900̱2 ferrofluids using a probe placed on the fixed top cover (-measured from the top).

Image of FIG. 8.
FIG. 8.

Startup of spin-up flow for EMG705̱0.

Image of FIG. 9.
FIG. 9.

Velocity profiles for EMG705̱0 at different heights in a container without a cover. The negative velocities indicate counter-rotation of fluid and field.

Image of FIG. 10.
FIG. 10.

Theoretical (a) translational and (b) spin velocity profile for zeroth, first, and composite asymptotic solution obtained from regular perturbation and with using ferrofluid properties for EMG705̱0.

Image of FIG. 11.
FIG. 11.

Log-log plots of the experimental extrapolated wall velocity vs Langevin parameter for EMG705̱0 and EMG900̱2.

Image of FIG. 12.
FIG. 12.

Log-log plots of the experimental normalized torque vs Langevin parameter for (a) EMG705̱0 and (b) EMG900̱0 ferrofluids and all their dilutions.

Tables

Generic image for table
Table I.

Physical and magnetic properties at room temperature for water and kerosene based ferrofluid.

Generic image for table
Table II.

Estimated magnetic particle diameters and effective relaxation times at room temperature for water and kerosene based ferrofluid.

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/content/aip/journal/pof2/20/5/10.1063/1.2907221
2008-05-28
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Spin-up flow of ferrofluids: Asymptotic theory and experimental measurements
http://aip.metastore.ingenta.com/content/aip/journal/pof2/20/5/10.1063/1.2907221
10.1063/1.2907221
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