Steady Flow of Power Law Fluids over a Pair of Cylinders in Tandem Arrangement

Abstract

The steady flow of incompressible power-law fluids over a pair of cylinders in tandem arrangement has been studied numerically. The field equations have been solved using a finite volume method based solver (FLUENT 6.2). In particular, the effects of the power-law index (0.4 ≤ n ≤ 1.8), Reynolds number (1 ≤ Re ≤ 40), and the gap ratio between the two cylinders (2 ≤ G ≤ 10) on the local and global flow characteristics such as streamline profiles, center line velocity, surface pressure coefficient, and individual and total drag coefficients, etc. have been studied in detail. The wake interference in conjunction with the power-law rheology exerts a strong influence on the flow dynamics at high Reynolds numbers, even in the steady-flow regime, whereas at low Reynolds numbers, the flow is influenced by the rheological behavior of the fluid. The increasing degree of shear-thinning behavior delays the flow separation, whereas early separation is seen in Newtonian and in shear-thickening fluids. The pressure coefficient distribution on the surface of the cylinders shows an intricate dependence on the power-law index, Reynolds number, and gap ratio. The shear-thinning behavior exerts stronger effects on the drag characteristics than those seen in Newtonian and shear-thickening fluids. Both upstream and downstream cylinders show smaller values of the individual and total drag coefficients than those for a single circular cylinder under otherwise identical conditions.