Flow of Newtonian and power-law fluids past an elliptic cylinder: a numerical study

Abstract

Extensive numerical simulations of the 2-D laminar flow of power-law fluids over elliptical cylinders with different aspect ratios have been carried out to establish the conditions for the onset of wake formation and the onset of vortex shedding. The continuity and momentum equations were solved numerically using FLUENT (version 6.3.26). The influence of the power-law index (0.3 ≤ n ≤ 1.8) and the aspect ratio (E = b/a; 0.2 ≤ E ≤ 5) of the cylinder on the critical values of the Reynolds number denoting the onsets of flow separation and vortex shedding are presented. For shear-thinning (n < 1) fluid behavior, the onsets of wake formation and vortex shedding are both seen to be postponed to higher Reynolds numbers as compared to those in shear-thickening fluids (n > 1). Also, the values of the Strouhal number (St_c) and the time-average drag coefficient (C¯_D) corresponding to the cessation of the steady-flow regime are presented. Velocity vector plots denoting the flow separation and vorticity profiles showing the vortex shedding are also included. The delineation of different flow regimes also helps identify the range of validity of some of the results on flow and heat transfer available in the literature.