Effects of polymer/surfactant additives on forced convective heat transfer in vortex shedding flow past a circular cylinder

Abstract

Abstract The unsteady incompressible flow of dilute polymer/surfactant solutions past an unconfined heated circular cylinder is studied to reveal the effects of these additives on convective heat transfer properties in the laminar and transitional vortex shedding regime. Both inelastic and elastic non-Newtonian features are considered and compared using two-dimensional numerical simulations. Inelastic power-law and purely viscoelastic Oldroyd-B as well as Giesekus and FENE-P constitutive models, exhibiting both shear thinning and elastic effects are adopted in the formulation. A finite element based software is used in simulations for the Reynolds number range 80 ≤ R e ≤ 300 , power-law index range 0.6 ≤ n ≤ 1 and Weissenberg number W i = 1 for weakly elastic solutions. Heat transfer enhancement is observed under inelastic shear thinning effects through an increase of the local and average Nusselt numbers, however purely viscoelastic effects lead to a decrease in the rate of convective heat transfer for the studied range of parameters. The increase in the Giesekus model mobility factor which is associated with anisotropic Brownian motion effects on polymer/surfactant molecules increases the heat transfer rate, and shifts the location of the maximum local Nusselt number to the front of the cylinder. However, increasing the FENE-P model finite extensibility parameter related to the maximum polymer chain length, decreases the local Nusselt number while the maximum heat transfer rate location moves towards the rear region on the cylinder surface. Temperature gradients decrease in the wake region under elasticity whereas shear thinning leads to an increase in the gradients and to the formation of clustered isotherms.