Effect Of Magnetic Field Dependent Viscosity Research Articles

Effect Of MFD Viscosity On Ferroconvection In A Fluid Saturated Porous Medium With Variable Gravity

<p>Convective instability of a horizontal ferromagnetic fluid saturated porous layer with magnetic field dependent (MFD) viscosity subjected to gravity field varying with distance in the layer is investigated. The fluid motion is described by the Brinkman model. The method of small perturbation is applied and the resulting eigenvalue problem is solved using the higher order Galerkin technique. The stationary instability is shown to be the preferred mode of instability and the resulting eigenvalue problem is solved by taking into account the realistic rigidrigid- isothermal boundary conditions. The study reveals that the effect of MFD viscosity is to delay the onset of ferroconvection and the stabilizing effect of MFD viscosity is reduced when the magnetic Rayleigh number is sufficiently large. In the presence of variable gravity, the effect of magnetic and non-magnetic parameters on ferroconvective instability is also discussed.</p>

Exploration of energy‐based volumetric heating on ferrothermal porous convection: Effects of MFD viscosity and boundary conditions

AbstractThe impact of energy‐based volumetric internal heating and magnetic field‐dependent (MFD) viscosity on the onset of ferrothermal porous convection for different types of boundary conditions is investigated. The lower and upper boundaries are considered to be either rigid or stress‐free. The lower boundary is insulating, while at the upper boundary a Robin type of thermal condition is applied. Besides this, a general type of boundary conditions is invoked on the magnetic potential. The stability eigenvalue problem is solved numerically using the Galerkin‐type of weighted residuals technique with the Rayleigh number, as the eigenvalue. The results obtained for different boundary combinations are found to be qualitatively similar though not quantitatively. The effect of Biot number, MFD viscosity, and porous parameters is to hinder, while the influence of internal heat source strength, magnetic number, and the nonlinearity of fluid magnetization is to advance the onset of convection. The rigid and conducting boundaries offer a more stabilizing influence on the onset when compared to stress‐free and insulating boundaries. The convection cells get contracted the most when the boundaries are rigid and also when the upper boundary is conducting. The results delineated under the limiting cases are found to be in good agreement with those available in the literature.

Analysis of water conveying iron(iii)oxide nanoparticles subject to a stationary magnetic field and alternating magnetic field

Present physical models describe the effects of magnetic field-dependent viscosity on unsteady water-based Fe3O4 magnetic fluid flow over a rotating and vertical moving disk. The first model represents the effect of magnetic field-dependent viscosity in the presence of a stationary magnetic field and the second model demonstrates the presence of an alternating magnetic field. However, the previous investigation of water conveying iron(iii)oxide nanoparticles flow in a rotating system is not available on the comparison of spatially variable magnetic field and alternating magnetic field on the velocity distribution in the presence of rotating and vertical moving disk. The variations in the viscosity due to the alternating magnetic field depend not only on the strength of the magnetic field but also on the frequency of the alternating magnetic field. This study might have a significant role in the improvement of the sealing of rotating shaft and study of magnetic field dependent viscosity of water conveying iron(iii)oxide nanoparticles are important for hyperthermia in the treatment of cancer disease. An alternating magnetic field generates higher friction on the disk as compared to the stationary magnetic field.

Study of magnetoviscous effects on ferrofluid flow

Present results show the effect of magnetic field-dependent viscosity on the flow of magnetic fluid due to a non-conducting rotating disk. Shliomis model has been used in the problem formulation. A similarity transformation has been used to reduce a set of partial differential equations into nonlinear coupled differential equations. The nonlinear coupled differential equations involved in the problem are solved numerically through mathematical modeling in COMSOL Multiphysics. The radial, tangential, and axial velocity distribution is presented for different values of the magnetic field-dependent viscosity parameter. Some theoretical results used in the model have verified mathematically. These theoretical results are useful to validate the Shliomis model for rotational motion. The results indicate that the Shiliomis model is more appropriate to study the ferrofluid flow due to an infinite rotating disk in comparison to the Rosensweig model.

Effect of magnetic field dependent viscosity on Soret-driven ferrothermohaline convection saturating an anisotropic porous medium of sparse particle suspension

Thermoconvective instability with Soret effect in multi-component fluids has wide range of applications in heat and mass transfer. This work deals with the theoretical investigation of the effect of magnetic field dependent (MFD) viscosity on Soret-driven ferrothermohaline convection heated and salted from below in an anisotropic porous medium subjected to a transverse uniform magnetic field. The resulting eigen value problem is solved using Brinkman model. An exact solution is obtained for the case of two free boundaries and the stationary and oscillatory instabilities are investigated by using linear stability analysis and normal mode technique for the vertical of anisotropic porous medium. The analysis has been made for different parameters like porosity, anisotropy, ratio of heat transport to mass transport, buoyancy magnetization, non-buoyancy magnetization, Soret parameter and Salinity Rayleigh number. The effect of MFD viscosity is assumed to be isotropy. It is found that the presence of MFD viscosity has a stabilizing effect, whereas magnetization has a destabilizing effect.

Brinkman ferromagnetic convection in a porous layer: Effect of MFD viscosity and magnetic boundaries

In the present study, the effect of magnetic field dependent (MFD) viscosity and different types of magnetic boundaries on the onset of ferromagnetic convection in a horizontal layer of Brinkman porous medium is investigated numerically using the Galerkin method. The simultaneous and isolation presence of buoyancy and magnetic forces on the stability characteristics of the system are emphasized. The study reveals that the linear stability of the system depends significantly on the types of magnetic boundaries. The rigid-paramagnetic boundaries are found to be preferred to the ferromagnetic ones in suppressing ferromagnetic convection. Besides, the system is more stable when the magnetic forces alone are present. In addition, increasing MFD viscosity parameter λ and decreasing magnetic number M1 and nonlinearity of fluid magnetization parameter M3 is to inhibit the onset of ferromagnetic convection in a porous medium. The critical wave number is found to be independent of λ, but increasing M1 and χ as well as decreasing M3 is to reduce the size of convection cells. At higher values of M3, the critical Rayleigh number and the corresponding wave number coincide for different magnetic boundaries.

Revolving Ferrofluid Flow under the Influence of MFD Viscosity and Porosity with Rotating Disk

In the present case, we have studied the effect of magnetic field-dependent viscosity (MFD) along with porosity on the revolving Axi-symmetric steady ferrofluid flow with rotating disk by solving the boundary layer equations using Neuringer-Rosensweig (NR) model. Here, we have calculated the velocity components and pressure for different values of MFD viscosity (k) and porosity (ε) with the variation of Karman’s dimensionless parameter α. Also, we have calculated the displacement thickness of the boundary layer and total volume flowing outward the z-axis. The numerical results which are obtained for various flow characteristics are shown graphically.

Effect of magnetic field-dependent viscosity on revolving ferrofluid

The effect of magnetic field-dependent viscosity on the revolving axi-symmetric steady flow of ferrofluid in a disc is investigated by solving the boundary layer equations using Neuringer–Rosenweig model. Besides numerically calculating the velocity components and pressure for different values of magnetic field-dependent viscosity with variation in dimensionless parameter α (Karman’s parameter), we also have calculated the thickness of the boundary layer and the total volume flowing outward the z-axis. Here, the solutions of non-linear differential equations are obtained in the form of asymptotic series.