Effects of axis ratio, nanoparticle volume fraction and its size on the momentum and heat transfer phenomena from an elliptic cylinder in water-based CuO nanofluids

Abstract

In this study, a detailed numerical investigation has been carried on the momentum and heat transfer phenomena from an elliptic cylinder, including the limiting cases of circular cylinder and flat plates, in streaming water based CuO nanofluids over the following ranges of conditions as: Reynolds number, 1 ≤ Re ≤ 40; nanoparticle volume fraction, 0 ≤ ϕ ≤ 0.06 and cylinder axis ratio, 0.1 ≤ AR ≤ 5.0 for two sizes of the nanoparticles, namely, 30nm and 60nm. The local flow field in the vicinity of the cylinder surface is visualized in terms of the streamline profiles, whereas the gross flow and heat transfer characteristics are presented in terms of the drag coefficient and Nusselt number respectively. All else being equal, the separation of the boundary layers is accelerated in 60nm CuO nanofluids as compared to that seen in water, whereas it is decelerated in 30nm CuO nanofluids. The total drag coefficient for an elliptic cylinder is always seen to be higher in nanofluids as compared to that seen in pure water. For 60nm CuO nanofluids, the Nusselt number always increases with the increasing values of ϕ, whereas for 30nm CuO nanofluids, it first increases and then decreases. Finally, simple analytical formulas for the total drag coefficient and average Nusselt number are provided which facilitate the interpolation of the present results for the intermediate values of Re,ϕ and AR.