Effects of elasticity on unsteady forced convective heat transfer of viscoelastic fluid around a cylinder in the presence of viscous dissipation

Abstract

The effects of elasticity on flow structures and forced convection heat transfer of a viscoelastic fluid around a cylinder were studied numerically using a finite volume method for the first time. In addition, the effects of viscous dissipation on flow and heat transfer parameters were studied over a wide range of Brinkman number (Br). The accurate non-linear Phan-Thien–Tanner model was used to describe the viscoelastic behavior of a polymer solution with a high retardation ratio (β = 0.6) over a wide range of Weissenberg (Wi) and Reynolds numbers (Re). The fluid properties were considered to be temperature-dependent. The results showed that the role of elastic effects in vortex shedding is a depreciator for Wi < 0.5 and an amplifier for Wi > 0.5. The Nusselt number was monotonically increased up to 52.2% with increasing Wi, β, Prandtl number (Pr), and Br over a wide range. The elastic forces affected the physical parameters by contrasting with the viscous forces so that the effects of elastic forces were weaker for high Reynolds numbers. Both hydrodynamic and thermal boundary layers were thinner in a viscoelastic fluid, compared to a Newtonian fluid. In addition, a correlation for variations of the drag coefficient with Wi and two correlations for variations of drag coefficient and Strouhal number with Re for Newtonian and viscoelastic fluid were proposed. Finally, the effects of Wi, Pr, Br, and model parameters on the Nu, St, drag, and lift coefficient and the distribution of stress components, velocity, and temperature were examined.