Simulations to Determine Laminar Loss Coefficients in Arbitrary Planar Dividing Flow Geometries

The goal of this study is to determine laminar stagnation pressure loss coefficients for planar dividing flow. These losses are of clear interest in understanding flow in microfluidic devices, in porous media, or other complicated laminar pore networks. There is no published set of pressure loss coefficients for arbitrary bifurcation geometries that occur in these networks. Additionally, the small number of bifurcation geometries that have been studied are for turbulent flow often found in fluid supply and drain systems. The pressure loss coefficients determined in this study allow realistic simulation of existing laminar flow networks or the design of these networks. This study focuses on a single inlet duct with two outlet ducts, which were allowed to vary in diameter, flow fraction, and angle — all relative to the inlet duct. Laminar stagnation pressure loss coefficients have been determined by simulating incompressible flow through 600 different geometries. In all cases, the flow is laminar in the inlet and outlet ducts. Simulations of the dividing flow geometries were done using FLUENT and a custom written computer code, which automates the process of creating flow geometries, of creating FLUENT input files, and of parsing FLUENT output. The outputs, pressure and velocity distributions at the inlet and outlets, have been averaged and then used to calculate pressure loss coefficients for each of the geometries and flow fraction scenarios simulated. The results for loss coefficient for the geometries considered range from 0.15 to 49. The loss coefficient for any geometry increases significantly as the flow fraction increases and as the duct size of an outlet duct relative to the inlet duct decreases. Less significant variation of the loss coefficient has been observed as a function of the angles of the exit ducts.