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Abstract: The dynamic rheological properties of viscoelastic magnetic fluids in externally applied uniform magnetic fields are investigated by a laboratory-made cone-plate rheometer in this study. In particular, the effects of the magnetic field on the viscoelastic properties (the complex dynamic modulus) of the viscoelastic magnetic fluids are studied. In the investigation, three viscoelastic magnetic fluids are made by mixing a magnetic fluid and a viscoelastic fluid with different mass ratios. As a supplementation to the experimental investigation, a theoretical analysis is also presented. The present study shows that the viscosity and elasticity of the viscoelastic magnetic fluids are significantly influenced by the magnetic field and the concentrations of the magnetic particles in the test fluids. Theoretical analysis qualitatively explains the present findings. [Copyright &y& Elsevier]

Abstract: In this article, natural convections of a magnetic fluid in a cubic cavity under a uniform magnetic field are investigated experimentally and numerically. Results obtained from experiments and numerical simulations reveal that the magnetic field and magnetization are influenced by temperature. There exist relative larger magnetization and magnetic forces in the regions near the upper wall and center inside the cavity than in the region near the bottom and side walls. A weak flow roll occurs inside cavity under the magnetic force, and it brings the low temperature fluid downward in the center region, and streams the high temperature fluid upward along the regions near the sidewalls. With the magnetic field imposed, the heat transfer inside the cavity is enhanced significantly compared to that without the magnetic field, and increasing the strength of the magnetic field the heat transfer is increased further. [Copyright &y& Elsevier]

In this article, the dynamics of ferrodroplet deformation and bubbles merging within the ferrofluid under a uniform magnetic field are studied through numerical simulations. A recently developed simplified multiphase lattice Boltzmann method (SMLBM) is used to capture the hydrodynamic behavior of ferrofluids, the Cahn-Hilliard (CH) equation is employed as the interface tracking algorithm, whose solution is also obtained within the lattice Boltzmann framework and a self-correcting procedure is used to solve the magnetic field along with conjugate boundary conditions for a smooth transition of magnetic permeability at the interface. A series of numerical simulations are performed for a range of magnetic field strength, magnetic susceptibility and Ohnesorge number (Oh), along with a comparison between obtained results and previous experimental and numerical results. The dynamical behavior of ferrodroplets and bubbles merging in ferrofluids is analyzed through the distribution of magnetic field and magnetic flux density, velocity contours, pressure variations, the magnetic energy density and the effect of inertia. Findings of this study may help to explain the mechanism of ferrodroplet deformation and merging of bubbles within the ferrofluid and provide a useful insight into the distribution of flow variables during these deformations and merging phenomena. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic body force in boiling two-phase temperature-sensitive magnetic fluid (TSMF) flow is known to effectively increase the driving force of magnetic fluid in a non-uniform magnetic field. Based on this mechanism, in the present study, a binary TSMF, which is a mixture of the TSMF and a low-boiling-saturation-temperature organic solution, is proposed to be used in a heat transport device to enhance its circulation. In order to see its performance in the heat transport device, the pressure difference at different heated temperatures, magnetic fields and inclination angles of the heating section are investigated experimentally and theoretically. Results showed that the driving force increases remarkably due to more gas phase appearing in the test fluid and the magnetization of it decreasing. At low magnetic field the driving force is enhanced greatly when the inclination angle is close to 60°, while at high magnetic field the driving force is remarkably enhanced due to the effect of the magnetic force in the inclination angle range from 0° to 30° and 60° to 90°. [Copyright &y& Elsevier]

Abstract: Experiment and numerical study were conducted to investigate the heat transfer characteristics of a thermo-sensitive magnetic fluid (TSMF) filled in a cubic container with a heat generating square cylinder stick inside and under a uniform magnetic field. The experimental results show that, regardless of the heat generating object sizes, the heat transfer characteristic of the TSMF is enhanced when the magnetic field is applied to the TSMF. However, the heat transfer of the TSMF becomes poor as the size of the inside heat generating object increases because the space where the fluids go through becomes narrower and the flow is obstructed when the heat generating object size becomes bigger. Numerical simulation based on the Lattice Boltzmann method confirmed the experimental findings, and disclosed more flow details of the natural convection of the TSMF inside cavity. [Copyright &y& Elsevier]