Turbulent flow in a 90° pipe junction: Part 2: Reverse flow at the branch exit

Abstract The turbulence structure of a water flow in the branch exit of a tee pipe junction has been investigated experimentally and numerically. A mass flow rate branch exit-to-inlet ratio of 50% was used. The Reynolds number based on the inlet bulk mean velocity and the pipe diameter D =50 mm was 1.26×10 5 . The numerical solution was conducted employing three models for turbulence, k – e , renormalization group theory (RNG) and Reynolds stress model, using a refined grid to model the smooth chamfer of radius, r =0.25 D as part of the physical tee junction. Within the branch exit the flow has a separation region with recirculation, which extends up to half of the diameter. In this paper the differences noticed between the numerical and experimental results and between the results from each model are discussed. The predicted recirculating flow was attached to the pipe wall up to 2.05 D downstream from the separation region, contrary to the 0.65 D experimentally observed. In the vertical direction, the experimental data gave evidence that the near-wall flows are substantially asymmetric.