Unsteady Cattaneo-Christov double diffusion of Oldroyd-B fluid thin film with relaxation-retardation viscous dissipation and relaxation chemical reaction

This paper investigates upper-convected Oldroyd-B fluid thin film flow over an unsteady stretching sheet considering modified viscous dissipation and chemical reaction. With Cattaneo-Christov double diffusion theory, the governing equations are obtained. Meanwhile, unlike the viscous dissipation of Newtonian fluid, depending on the constitutive relation of Oldroyd-B fluid, the relaxation-retardation viscous dissipation is developed. Furthermore, the chemical reaction with relaxation-time characteristic has been discussed firstly. The governing equations are solved by a new efficient analytical method known as double-parameter transformation expansion method (DPTEM). Some interesting results can be revealed. Increasing unsteadiness parameter causes a rise in film thickness for beta(2) > beta(1), but a decline as beta(2) < beta(1). Moreover, the temperature enhances with rising values of retardation time when beta(2) < beta(1), while the contrary behaviors are observed when beta(2) > beta(1). Furthermore, unsteadiness parameter has the opposite influences on the concentration in the cases of beta(2) > beta(1) and beta(2) < beta(1). (C) 2018 Elsevier B.V. All rights reserved.