On the Rheology and Hydrodynamic Investigations of Magnetic Fluid

Abstract: In this paper,the preparation and rheological property of oil-based Fe_3O_4 magnetic fluid were studied.The hydrodynamic property and constitutive equations of the magnetic fluid were also investigated.(1)Using one-step method,the kerosene-based magnetic fluid and silicon-oil-based magnetic fluid were prepared.Then microwave irradiation was used to enhance the crystallization of Fe_3O_4 magnetic nanoparticles.The physical properties of magnetic fluid prepared under different methods were investigated.(2)The rheological property of the magnetic fluid was investigated using a rotating rheometer attached with a custom-built solenoid coil.The magnetic fluid showed shear-thinning behavior that could be described by the Herschel-Bulkley model.(3)Based on the microstructure during the application of magnetic field to magnetic fluid, the interactive force between the chains when the particles form chains aligned the field direction due to the dipole moment was analyzed.And a theoretical model for the yield stress threshold under applied magnetic field was derived.The results obtained by the theoretical model were well matched with the experimental measurements.Finally,a general constitutive equation was proposed to calculate the shear stress of magnetic field.(4)Two-dimensional numerical simulation was performed to investigate the ejection phenomena of the magnetic fluid from a capillary.The influence of the magnetic field on the formation and breaking of liquid filament was also investigated.Then a system composed a self-made experimental apparatus and a high speed CCD camera was used to study the hydrodynamics of the magnetic fluid.The measured results are validated by the experimental findings.(5)A system composed of a self-made experimental apparatus and a high-speed CCD camera was used to study the hydrodynamics of the two-layer flow of magnetic fluid and non-magnetic silicone oil.It was found that the model used to simulate the interface can well match the shape of interface surface obtained by CCD camera…
Key words: Magnetic fluid; nanoparticles; surface modification; rheology; yield stress

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