Effect of variable viscosity and thermal conductivity on water-carrying iron (iii) oxide ferrofluid flow between two rotating disks

The paper represents the potential significance of magnetic field-dependent viscosity, temperature-dependent viscosity, and variable conductivity on water-carrying iron (iii) oxide ferrofluid flow between two parallel stretchable rotating disks under the influence of a stationary magnetic field. This problem develops the understanding of the swirling flow of ferrofluid in the presence of magnetization force. The influence of variable viscosity and variable conductivity in the swirling flow of ferrofluid is useful in sealing the rotating shaft and heat transfer enhancement applications. We use similarity transformation to reduce the governing equations into non-dimensional nonlinear differential equations. The transformed non-dimensional boundary layer equations are solved numerically using finite element procedure in COMSOL Multiphysics. Under the influence of the magnetic field, the magnetic torque acting in the flow and enhancement in the volume concentration of iron (iii) oxide nanoparticles both enhance the viscosity of ferrofluid. Increasing temperature-dependent viscosity parameters reduce the viscosity of ferrofluid. However, variable conductivity parameter increases the temperature in the flow. The magnetic torque reduces the radial and axial velocity distributions and magnetization force enhances the velocities. Friction on the disk and local heat transfer mainly depends on the rotation speed and stretching of the disks, and magnetization force.