Flow behavior and drag prediction for power-law fluids around rectangular cylinder: Effect of aspect ratio and Reynolds number

Understanding the interaction between non-Newtonian fluids and bluff bodies is pivotal for advancing fluid dynamics, yet the behavior of such fluids around rectangular cylinders with varying aspect ratios (α) remains underexplored. This study addresses this gap by systematically investigating the steady-state flow characteristics of power-law non-Newtonian fluids across a wide range of aspect ratios (α = 0.1–10) and power-law indices (n = 0.6–1.4) under low Reynolds numbers (Re = 5–40). Using computational fluid dynamics and the finite volume method, the study uncovers the intricate interplay between geometry, flow properties, and fluid behavior. The results indicated that the maximum vorticity at the leading edge decreases by approximately 67.55%, while at the trailing edge, it decreases by around 83.33% as aspect ratio increases from 0.1 to 10 at Re = 5. The pressure coefficient (Cp) and vorticity contour are plotted along with Q-criterion line. Reattachment length diminishes by 86.76% as α increases from 0.1 to 10 for n = 0.6 and Re = 20. The drag coefficient (CD) shows complex dependencies on both α and n, with its maximum observed at α = 10 and n = 0.6, while the minimum is observed when α = 0.1 and n = 0.6, indicating a decrease in 64.91% from α = 10 to α = 0.1. Further, a regression analysis was performed to develop a predictive model for the CD as a function of α, n, and Re. This research offers novel perspectives on the effects of non-Newtonian fluid rheology and rectangular cylinder geometry at low Re, offering a foundation for further theoretical and experimental exploration.