Anisotropic turbulent flow of water through converging wavy-aluminum-circular pipe with five half-cycles: insight into the significance of four-branch minor-inlet angle

Abstract

Accurately predicting turbulent water flow in duct systems remains a challenging problem, particularly when anisotropic turbulence effects are significant. Bridging the gap between industrial applications and academic research requires a deeper understanding of such complex flows. This study investigates a less commonly analyzed configuration involving a horizontal aluminum duct transitioning into a converging wavy duct. The wavy section consists of 2.5 full sinusoidal periods, ending in a reduced outlet diameter. In addition, the effect of incorporating four minor/secondary inlets, arranged as branches at different angles, was examined and presented herein. Aluminum was selected for its low density and corrosion resistance, which are beneficial in experimental and industrial setups. Initially, the duct was analyzed in an unbranched configuration. The study then progressed to include the four secondary/minor branch inlets at various angles. The simulation results were validated by comparison with a solution for a simple flow in a 70 mm duct. Additional verification was provided by employing other CFD codes, along with grid convergence index and mesh sensitivity analyses, improving the confidence in the simulation results. Branch angles influences turbulence intensity depending on flow conditions and angle magnitude. Sharper branch angles are particularly effective, inducing greater turbulence at the converged outlet. Higher inlet temperatures and velocities lead to increased Reynolds stress due to enhanced energy transfer and elevated turbulent kinetic energy. Specifically, an increase in inlet velocity at a 45° branch angle further augments turbulent momentum transfer, resulting in more controlled mixing along the duct.