Magnetic effect on thermo-fluid-dynamics of two-layered fluid systems: Simulations and experiments

Fluid dynamics and heat transfer of two-layered immiscible fluid systems is of great importance in a variety of industrial as well as space-exploration applications. Control and optimization of convective thermo-fluid-dynamics of such systems need a complete understanding of all phenomena, especially those induced by surface tension at the fluid interface. The present work is focused on convective flow and heat transfer in a cavity heated from the sides, which is subject to both buoyancy and thermocapillary effects in addition to the influence of magnetic field applied for flow control. With the encapsulant liquid posing magnetic properties, a magnetic force can arise to either enhance or reverse the gravity effect when the cavity is placed in a non-uniform magnetic field. The driving force exploited in the present study is based on the change of magnetic susceptibility of a magnetic material and thus it does not reduce as the system flow reduces unlike the approaches employing the Lorentz's force.; This study is based on two nondimensional schemes. The effects of the fundamental parameters on the thermo-fluid-dynamics and the interfacial shape of the system have been analyzed. The investigation reveals that the Marangoni convection can significantly influence the velocity distribution in the cavity. It also shows that introduction of a magnetic field can easily promote or hinder the Marangoni effect, that is, to further increase or decrease the global convective motion. The effect of the magnetic body force of the upper magnetic fluid has a difficulty to penetrate through the interface of the two fluids, so care must be taken in selecting the geometry and the fluids with proper characteristics when optimizing the system for industrial applications. It has been shown that the interfacial velocity can be altered as much as 100% and that even a small change in the velocity field can produce significant changes in temperature distribution. This in turn affects the local Nusselt number and thus the global heat transfer reducing it or enhancing it by up to 100%.; Results of the experiments and comparison with numerical calculations are also provided. The theoretical-numerical and experimental results are in good qualitative agreement, thus confirming the feasibility of using magnetic fluid and magnetic field to control the thermo-fluid-dynamics of two-layered fluid systems.