Ferrohydrodynamic Instability of a Couple Stress Magnetic Fluid Layer Under the Influence of Time-Dependent Sinusoidal Magnetic Field

Abstract

The commencement of convective motion in a horizontal couple-stress ferrofluid exposed to magnetic field modulation has been examined. Making use of isothermal boundary condition, the subsequent eigenvalue problem is attacked by adopting regular perturbation technique with minimum modulation amplitude. Thermal Rayleigh number correction is determined by the modulation frequency, magnetic force, couple-stress parameter and Prandtl number. The impact of various physical factors is perceived to be significant at intermediate magnetic field modulation frequency. It is found that by fine tuning the modulated magnetic frequency, we could either speed up or slow down the commencement of ferroconvection. The problem sheds some light on ferromagnetic fluid applications with a time-varying magnetic field.