Laminar flow dominates microscale and milliscale applications. This work is focused on laminar energy losses in junctions (bifurcations). Reynolds number plays a dominant role in energy losses for laminar flow. The physical cause of these energy losses is entropy generation. This paper analyzes the energy losses in junctions by considering the entropy generation.

This paper documents results from computational fluid dynamics (CFD) simulations of laminar flow in planar junctions. The junctions studied consisted of circular pipes with two outlets and one inlet tube with Reynolds numbers ranging from one to 1000. A general technique has been developed to produce computer 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 entropy generation has been determined in junctions from simulation results for the velocity field. Results for entropy generation as a function of geometry and Reynolds are presented. Energy loss coefficients are derived from the simulations and compared to experimental measurements of energy losses in microscale junctions.

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