Dynamical flow characterization of single-phase flow in a converging-diverging channels*

We present a three-dimensional numerical model to investigate the dynamics of single-phase flow in a parallel branched microchannel, accounting for variable geometric dimensions of constrictions. The study aims to explore the complexities of fluid flow in microdevices featuring networks of branches and narrow passages. The results reveal non-linear fluctuations in velocity, pressure, acceleration, and shear stress along the flow direction, with a strong dependence on the angles of convergence or divergence at the constrictions. A modified Reynolds number is introduced as the primary parameter governing flow transitions, providing a novel approach to understanding the impact of geometric characteristics in microchannels with converging/diverging constrictions. Our findings show a significant increase in inertial forces, a phenomenon not typically observed in simple microchannels. Additionally, we analyze entropy generation and efficiency concerning the Reynolds number. The results suggest that microdevices with larger converging-diverging angles and smaller width ratios are more favorable, offering reduced pumping power and improved energy efficiency. These insights are critical for guiding design modifications aimed at enhancing the efficiency of micropumps or microvalves.