Unsteady flow of thin nanoliquid film over a stretching sheet in the presence of thermal radiation

Abstract

Unsteady two-dimensional flow of a thin nanoliquid film over an impulsively stretching sheet is studied in the presence of thermal radiation. It is assumed that the sheet is either heating or cooling along the stretching direction. The nonlinear governing set of equations is solved analytically by the singular-perturbation technique. It is observed that the film thinning rate decreases with the increase of the nanoparticle volume fraction. It is also found that the rate of film thinning decreases with the increase of the radiation parameter in case of heating and the opposite phenomenon is observed for cooling of the sheet. The film thinning rate increases with the increase of the nanolayer thickness but decreases with the increase of the nanoparticle radius when the sheet is heated. Moreover, it is observed that the temperature gradient Tz changes its sign within the film in the presence of thermal radiation.