56 research outputs found
Numerical modeling of a static magnetic fluid seal subject to diffusion of ferromagnetic particles
Because magnetic fluid is a stable colloidal suspension of small ferromagnetic particles
in a carrier liquid, its macroscopic interaction with an external nonuniform magnetic field is determined by the force acting on each separate particle
ADI approach to the particle diffusion problem in magnetic fluids
The present study is devoted to the development of an ADI approach to simulate two-dimensional time-dependent diffusion process of ferromagnetic particles in magnetic fluids. Specific features of the problem are the Neumann boundary conditions. We construct an ADI scheme of formally second order accuracy approximation in time and space. It is proved that the scheme is absolutely stable and it has the accuracy in the energy norm of the second order in time and the order 3/2 in space. The numerical results of a test problem indicate that the convergence rate in space is of the second order as wel
Instability of magnetic fluid in a narrow gap between plates
The behavior of a layer of magnetic fluid in a plane capillary subjected to a uniform magnetic field is studied numerically. Two different types of instabilities arise as the intensity of the magnetic field increases. For small contact angles the layer breaks along the capillary axis and spreads over the capillary wall whereas for large contact angles the layer elongates in the central part up to its separation from the walls. Critical parameters and shapes are studied by solving the coupled nonlinear system of differential equations numericall
Influence of diffusion of magnetic particles on stability of a static magnetic fluid seal under the action of external pressure drop
We derive a mathematical model for studying the stability of magnetic fluid seal under the action of external pressure drop in the static case. We propose a numerical algorithm for computing the free surface shape under the influence of diffusion of magnetic particles. We include also the case in which the particle concentration achieves its maximum corresponding to the dense packing of the particles. Numerical experiments for various sets of parameters give interesting insights in the dependence of the burst pressure on different parameter
Numerical study of the Rosensweig instability in a magnetic fluid subject to diffusion of magnetic particles
The present study is devoted to the classical problem on stability of a magnetic fluid layer under the influence of gravity and a uniform magnetic field. A periodical peak-shaped stable structure is formed on the fluid surface when the applied magnetic field exceeds a critical value. The mathematical model describes a single peak in the pattern assuming axial symmetry of the peak shape. The field configuration in the whole space, the magnetic particle concentration inside the fluid and the free surface structure are unknown quantities in this model. The unknown free surface is treated explicitly, using a parametric representation with respect to the arc length. The nonlinear problem is discretized by means of a finite element method for the Maxwell's equations and a finite-difference method for the free surface equations. Numerical modeling allows to get overcritical equilibrium free surface shapes in a wide range of applied field intensities. Our numerical results show a significant influence of the particle diffusion on the overcritical shape
Equilibrium shapes of a ferrofluid drop
A numerical solution strategy for calculating equilibrium free surfaces of a ferrofluid drop under the action of uniform magnetic fields is proposed. Based on this strategy, drop shapes of nonlinear magnetizable fluids are obtained numerically in a wide range of field intensities and compared with existing theoretical result
Numerical modeling of the equilibrium shapes of a ferrofluid drop in an external magnetic field
A numerical solution strategy for calculating equilibrium free surfaces of a magnetic fluid under the action of a magnetic field is proposed and applied to determine shapes of a linear magnetizable ferrofluid drop in a uniform magnetic field. Hysteresis phenomena for the drop deformation and the drop shapes with ends, close to conical, were observed numericall
The effect of magnetophoresis and Brownian diffusion on the levitation of bodies in a magnetic fluid
New aspects related to the redistribution of magnetic particles concentration in a magnetic fluid caused by magnetophoresis and Brownian diffusion in a nonuniform magnetic field are considered. These aspects deal with the influence of these processes on pressure redistribution and levitation of bodies in a magnetic fluid. It is shown that due to these processes the pressure force acting on bodies changes significantly with time and can be reduced dozens of percent if compared to a homogenous flui
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