Rotationally symmetric hybrid-nanofluid flow over a stretchable rotating disk

Abstract

Owing to the advanced thermophysical properties of hybrid nanofluids and stabilizing nature of surface stretching, the problem of rotationally symmetric flow and heat transfer induced over a rotating disk is extended to the case of a stretchable disk, considering Cu and TiO2 nanoparticles suspended in water. In addition, this study deals with four distinct shapes (sphere, brick, cylinder, platelet) of Cu and platelet-shaped TiO2 nanoparticles to elucidate the shape effects. Different from the traditionally applied external vertical magnetic field, the flow is investigated under the influence of a horizontal magnetic field. Moreover, the impact of solar radiation parameters is taken into account to inspect the radiated hybrid nanoparticles. For the same sense and weak & opposite sense (−0.161≤β≤0, here β signify the angular velocity ratio of fluid to disk ) of fluid and disk rotation, solutions are obtained in all cases. However, in the case of strong and opposite sense of rotation, physically acceptable solutions exist after a critical value of the stretching parameter (for example, when β=−0.8,Scr≈0.6). These numerical results have significant engineering applications to fluid flows in rotating machineries such as rotating heat exchangers, rotating disk air cleaners and gas turbine engines.