Effects of Transpiration on the Unsteady Separated Stagnation-Point Flow and Heat Transfer Over a Moving Porous Plate

The combined influence of normal transpiration and tangential movement of a porous surface on the unsteady separated stagnation-point flow and heat transfer of a viscous fluid is studied. This study is based on five physical parameters, namely (i) flow strength parameter a, (ii) suction/injection parameter d, (iii) plate velocity parameter lambda, (iv) unsteadiness parameter beta, and (v) Prandtl number Pr. This analysis shows an interesting relation beta = 2a which allows us to derive some closed-form analytic solutions depending upon the unlikely values of d. For suction d > 0, two attached flow solutions (AFS) without point of inflection are found in the range (-ad(2)/4-3<lambda<-3), whereas for lambda > -3 only one solution of the same type is found for any given value of d. Besides them, the numerical computations reveal two types of AFS-one without and the other with a point of inflection in the range (-1.24658 <= lambda <= -1.07) when d = beta = 0. The present analysis confirms the nonexistence of the second attached flow solution after a certain value of suction d depending upon the choice of the values of lambda in this range. A reverse flow solution (RFS) along with the above two solutions is found for a negative value of beta which continues even for large rate of suction d. The asymptotic solutions of this flow problem have also been derived for large values of d which provide with the exact results after a certain value of d depending upon the values of the other parameters.