Stagnation point flow with heat transfer and temporal stability of ferrofluid past a permeable stretching/shrinking sheet

In this paper, the hydromagnetic stagnation point flow and temporal stability of Fe3O4- water ferrofluidover a convectively heated permeable stretching/shrinking sheet is theoretically investigated.The model equations of momentum and energy balance are obtained and transformed into ordinary differential equations using appropriate similarity variable. Using shooting method together with Runge-Kutta-Fehlberg numerical scheme the model nonlinear boundary value problem is tackled numerically. Pertinent results with respect to the basic steady flow velocity, temperature, skin friction and Nusselt number are obtained graphically and in tabular form. It is found that a critical value of shrinking parameter (λc) exists below which no real solution can be found. In addition, dual solutions (upper and lower branch) are observed fora range of shrinking/stretching parameter (λc<λ< 1), while for the stretching case (λ≥ 1), the solution is unique. The obtained steady state solutions are examined for temporal development of small disturbances. The smallest eigenvalues reveal that the upper solution branch is stable and physically reliable while the lower solution branch is unstable and unrealistic. Both suction and magnetic field widen the range of the shrinking parameter for which the solution exists and boost the flow stability while nanoparticles volume fraction lessens it. © 2018 Trans Tech Publications, Switzerland.