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Title: Magnetorheological effect in the magnetic field oriented along the vorticity

In this work, we have studied the magnetorheological (MR) fluid rheology in the magnetic field parallel to the fluid vorticity. Experimentally, the MR fluid flow was realized in the Couette coaxial cylinder geometry with the magnetic field parallel to the symmetry axis. The rheological measurements were compared to those obtained in the cone-plate geometry with the magnetic field perpendicular to the lower rheometer plate. Experiments revealed a quasi-Bingham behavior in both geometries with the stress level being just a few dozens of percent smaller in the Couette cylindrical geometry at the same internal magnetic field. The unexpectedly high MR response in the magnetic field parallel to the fluid vorticity is explained by stochastic fluctuations of positions and orientations of the particle aggregates. These fluctuations are induced by magnetic interactions between them. Once misaligned from the vorticity direction, the aggregates generate a high stress independent of the shear rate, and thus assimilated to the suspension apparent (dynamic) yield stress. Quantitatively, the fluctuations of the aggregate orientation are modeled as a rotary diffusion process with a diffusion constant proportional to the mean square interaction torque. The model gives a satisfactory agreement with the experimental field dependency of the apparent yield stress andmore » confirms the nearly quadratic concentration dependency σ{sub Y}∝Φ{sup 2.2}, revealed in experiments. The practical interest of this study lies in the development of MR smart devices with the magnetic field nonperpendicular to the channel walls.« less
Authors:
; ; ; ;  [1] ; ;  [2] ;  [3]
  1. Laboratory of Condensed Matter Physics, CNRS UMR7336, University of Nice-Sophia Antipolis, 28 Avenue Joseph Vallot, 06100 Nice (France)
  2. Department of Applied Physics, University of Granada, Campus de Fuentenueva, 18071 Granada (Spain)
  3. Department of Mathematical Physics, Ural Federal University, 51 Prospekt Lenina, 620083 Ekaterinburg (Russian Federation)
Publication Date:
OSTI Identifier:
22360152
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Rheology; Journal Volume: 58; Journal Issue: 6; Other Information: (c) 2014 The Society of Rheology; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CONCENTRATION RATIO; DIFFUSION; FLUCTUATIONS; FLUIDS; GEOMETRY; MAGNETIC FIELDS; ORIENTATION; STOCHASTIC PROCESSES; STRESSES; SUSPENSIONS