Exact solutions of Stokes' second problem for hybrid nanofluid flow with a heat source

Abstract

In this study, Stokes' second problem for Cu-Al2O3/water hybrid nanofluid is considered along with the effects of buoyancy force and a heat source. Using Laplace transforms, transient velocity, skin friction coefficient, and local Nusselt number are established in closed forms involving exponentials and error functions. The exact solutions have been compared with the numerical solutions as well as with available exact solutions, which show excellent agreement. It is found that the temperature, skin friction coefficient, and local Nusselt number are strongly affected and increased owing to the increase in the volume fractions of copper and alumina nanoparticles and heat source parameter. On the other hand, the mixed convection parameter noticeably enhances the flow velocity. When the heat source is absent, the skin friction coefficients are oscillating and the heat transfer approaches an asymptotic value. However, for a higher heat source parameter, when time increases, the amplitude of oscillation of the skin friction coefficients gradually increases and the magnitude of heat transfer exponentially increases. Both eventually go to infinity after a long period of time.