Significance of Reynolds Number Consistency in Non-Newtonian Hemodynamic Simulations: Insights from Fontan Circulation.

The non-Newtonian properties of blood flow have been widely debated in hemodynamic research, particularly for congenital heart defects. Many studies comparing Newtonian and non-Newtonian models have overlooked dimensional group consistency, resulting in comparisons influenced by inconsistent Reynolds numbers rather than viscosity effects. In this study, we address this issue by applying a generalized Reynolds number formulation to ensure consistent dimensionless group comparisons. We compare flow structures and hemodynamic metrics in 20 pediatric Fontan circulations using the non-Newtonian Casson model against both conventional and generalized Reynolds number-corrected Newtonian models. Our results show that the conventional Newtonian model significantly overestimates flow rotation and underestimates stagnation regions, potentially misrepresenting thrombosis risk. The generalized Reynolds number method, however, predicts flow structures, wall shear stress, and energy-based metrics more in line with the non-Newtonian model. Percentage of power loss estimates from the generalized method (17.7 [10.1, 22.7];