Unsteady stagnation-point boundary layer flows of power-law fluids over a porous flat plate

The problem of unsteady stagnation-point flows of power-law fluids over a porous flat plate with mass transfer is considered with a view to examine the rheological behaviors of the fluids. This study is completely based on the four physical parameters, namely, flow strength parameter a, mass transfer parameter d, unsteadiness parameter beta and non-Newtonian power-law index n. For d = 0, the numerical results of this analysis reveal the existence of two types of solutions - one is attached flow solution (AFS) and the other is reverse flow solution (RFS) in a definite range of n (0 < n <= 2) when (a, beta) = (1, -1). The present analysis confirms that the velocity profile for any dilatant fluid (n > 1) matches smoothly with the free stream velocity for a suitable amount of blowing d(< 0) depending upon the values of n. We will also discuss the asymptotic behaviors of the boundary layer flows for large values of d, i.e., for d -> +/-infinity. The asymptotic analysis ensures the existence of the above two solutions for large values of suction d > 0, whereas the boundary layer solution is terminated after a certain value of blowing d < 0, dependent on the values of beta(< 0) and n. Below this critical value of blowing d, this unsteady flow problem also provides us with a solution which does not appear to have a boundary layer character.