Momentum and heat transfer characteristics of a rotating elliptical cylinder in vortex shedding flow of power-law fluids

Abstract

A numerical analysis is carried out to comprehend the fluid flow and heat transfer phenomena of non-Newtonian power-law fluid flow around a rotating elliptic cylinder. The investigations are accomplished for parameters, namely, the aspect ratio of the cylinder, e=0.1; the rotational speed of the cylinder, 0.5≤α≤2.0; the Reynolds number, Re=100; the power-law index, 0.4≤n≤1.6; and the Prandtl number, 1≤Pr≤100. A detailed vorticity and isotherm patterns are presented to demonstrate the vortex shedding and heat transfer phenomenon around the cylinder. The results clearly show the strong dependency of fluid behaviors and rotational speed on flow and heat transfer phenomena. At a low rotational speed (α≤1.0), the standard vortex-shedding patterns appear. The behavior of the fluid mainly affects the size and strength of the vortices. At a higher rotational speed (α > 1.0), a hovering vortex (HV) appears for Newtonian and shear-thinning fluids. The shear-thinning tendency of the fluid encourages the formation of HV; however, the HV is not observed for shear-thickening fluids. Due to the rotational motion of the cylinder, the surface Nusselt number varies in a periodic manner with time/orientation. As expected, the Prandtl number (Pr) and shear-thinning (n<1.0) behavior of the fluid encourage the heat transfer from the cylinder. The rotational motion of the cylinder also favors the heat transfer phenomena. Finally, a correlation is presented for the time average surface Nusselt number (Nuavg) as a function of the Prandtl number (Pr), fluid behavior (n), and rotational speed (α).