Milli-Scale Junction Flow Experiments

Laminar flow is increasingly important area of study as it dominates microscale and milliscale applications in devices such as microvalves, pumps, and turbines and in biomedical applications such as stents and biological flows. Studies of pressure losses in junctions have mostly been focused on turbulent flow conditions that exist in larger scale piping systems. There is a need for laminar flow studies of energy losses in junctions so that engineers can better predict, design, and analyze flow in microscale and other small scale systems. Unlike in the turbulent regime, Reynolds number plays a dominant role in energy losses for laminar flow, so new studies should document the effects of Reynolds number. This paper documents laminar flow experiments in a milliscale junction. This work builds on previous experience of the authors in computational fluids dynamics simulations of junctions. The planar junction under study consists of a circular tubes with two outlets and one inlet. A general technique has been developed to produce computer and physical models of junctions in which the inlet tube size is set, but the outlets are allowed to vary in size and angle relative to the inlet tube. A generalized algorithm has been implemented to create three-dimensional models of the junctions for both computational and experimental studies. The junction test sections for experiments are milled from cast acrylic in two pieces to match three-dimensional computer models. The test sections are placed in a system that provides steady-state flow of water to test sections and has been designed to measure pressure losses and flow rates through the test section.