Numerical study of the effect of blockage ratio in forced convection confined flows of shear-thinning fluids

In this work, the fluid dynamics and heat transfer of time-dependent flows with shear-thinning behaviour over two confined square cylinders in tandem arrangement are studied numerically. The case studies include two- and three-dimensional flows under a wide range of power-law indices, 0.25 <= n <= 1.0, and blockage ratios, beta = 0.50, 0.66 and 0.80, for a fixed Reynolds number of Re = 100 and Prandtl number of Pr = 10. The fluid dynamic analysis includes detailed qualitative and quantitative comparisons between the different fluids and blockage ratios, where streamlines, viscosity fields, and lift and drag coefficients are presented. Moreover, a detailed study of the route from laminar time-dependent to chaotic flows is included. It was determined that the flow exhibits a transition from laminar to chaotic by decreasing the power-law index (n) and increasing the blockage ratio (beta). With respect to the thermal analysis, isotherms and Nusselt numbers are compared between the different case studies. This analysis demonstrates that the average Nusselt numbers increased in chaotic flows. The three-dimensional cases confirmed the results proposed for the two-dimensional case.

Automated summary

This study numerically investigates the fluid dynamics and heat transfer of time-dependent flows with shear-thinning behavior over two confined square cylinders in tandem arrangement, showing a transition from laminar to chaotic flow with decreasing power-law index and increasing blockage ratio. Thermal analysis demonstrates an increase in average Nusselt numbers in chaotic flows, and results from the three-dimensional cases confirm those proposed for the two-dimensional case.