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ECOULEMENT DES FLUIDES MAGNETIQUES DANS DES CAPILLAIRES ET MILIEUX POREUX SOUS L'EFFET D'UN CHAMP MAGNETIQUE

Abstract : The objective of the study is to establish the laws of the magnetic field effect on the flow of magnetic fluids in capillaries and capillary-porous media as well as to investigate mechanisms of the flow control. We study two types of magnetic fluids, namely ferrofluid and magnetorheological fluid.
The efficiency of the control of the magnetic fluid flows in capillaries and capillary-porous media by means of the magnetic field has been proofed and three mechanisms of such control have been considered, namely the magnetic field effect on a free surface, on the rheology of these fluids, and the effect of the magnetic force that attracts the fluid or its components to the domain of higher fields. The behavior of the uniform magnetic field effect on static and dynamic characteristics of a magnetic fluid free surface in a capillary have been established. A two times decrease in the pressure jump on the meniscus takes place in the magnetic field longitudinal relative to the capillary axis. A decrease in the pressure jump in the transverse magnetic field causes a deceleration of the magnetic fluid penetration into capillary. It points out a possibility of the fill-up time control within the range of 60%.
The theoretical model of the plane shear flow of a MR fluid with suspended chain-like structures has been generalized to the case of an uniform magnetic field making an arbitrary angle with the velocity gradient. The dynamic yield stress versus the magnetic field orientation dependencies have been obtained on the base of this model. These dependencies allowed us to calculate velocity profiles and discharge curves of the pressure driven flows of MR fluids in capillaries and capillary-porous media in the presence of uniform magnetic field of an arbitrary orientation. Experimental discharge curves have also been obtained; they confirmed the theoretical ones reasonably well and pointed out a possibility to control the pressure difference within the range of 1000 times.
We have applied the model of multiphase flows in order to simulate a blockage of MR fluid flow through a capillary under highly non-uniform magnetic field. We have found theoretically and experimentally that the pressure where the flow stops is near two times less than the pressure required to restart the flow.
Results of the study present a theoretical base for making new adaptive technical systems including active systems of vibroprotection.
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Contributor : Pavel Kuzhir <>
Submitted on : Sunday, March 20, 2005 - 1:10:37 PM
Last modification on : Wednesday, October 14, 2020 - 4:23:46 AM
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Pavel Kuzhir. ECOULEMENT DES FLUIDES MAGNETIQUES DANS DES CAPILLAIRES ET MILIEUX POREUX SOUS L'EFFET D'UN CHAMP MAGNETIQUE. Matière Condensée [cond-mat]. Université Nice Sophia Antipolis, 2003. Français. ⟨tel-00008824⟩

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