Pressure Drop and Vortex Size of Power Law Fluids Flow in Branching Channels with Sudden Expansion

Three dimensional flows of complex non-Newtonian fluids in sudden expending pipes are numerically investigated in this paper. The distribution channels have one or multiple inlet pipes and one outlet pipe. The working fluids have a shear thinning behavior modeled by the Ostwald De Waele law. The effects of different parameters on the flow fields and pressure drop are explored. It concerns the effect of Reynolds number Re (from 0.1 to 600), power law index n (from 0.4 to 1), number of branching channels (nb = 1, 2, 3 and 4), spacing between the branching channels (l/D = 0.1, 0.2, 0.3 and 0.4) and the expansion ratio (d/D = 0.2, 0.35, 0.5, 0.6 and 0.8). Three-dimensional complex flows were observed in the downstream expansion for such multiple branching systems, especially when the spacing l/D is small, where an asymmetry of flows is observed and a third recirculation loop is formed. A considerable increase in pressure drop is found with the rise of Reynolds number, with increased power law index and decreased expansion ratio. However, only a slight increase is observed with decreased spacing ratio and it remained almost the same with increased number of branching channels.