Computational Fluids Dynamics of air and water flows subjected to turbulence and confronted with cold fronts in a three-inlet-T-junction duct followed by two 90-degree elbows connected by a straight section of adjustable length (C-shaped elbow)

This study examines air and water flows in a three-inlet T-junction duct followed by two 90° elbows connected by a straight section of adjustable length (C-shaped elbow), with a particular focus on the impact of the straight section  length between the two 90° elbows. The analysis focuses on the behavior of the fluids (air and water) along the duct axis (x, y, z=0), after the mixing zone (at 70 mm), upstream of the first elbow, and at the duct outlet. The numerical solution is based on the realizable k-Ꜫ viscous turbulence model coupled with the energy equation, implemented in Ansys Fluent 2024R2. Three straight section length cases were studied: Case I (L= 20 mm), Case II (L=50 mm), and Case III (L=100 mm). According to the results obtained, the c-bend, consisting of two 90° elbows connected by the straight section, intensifies the turbulence within the flow, with effects depending on the thermophysical characteristics of the fluid (density, thermal conductivity, kinematic viscosity, etc.). The straight section connecting the two 90° elbows moderates the combined dynamic and thermal disturbances of the successive elbows. If it is too short, it aggravates the disturbances; if properly dimensioned, it acts as a stabilizing buffer zone, improving the thermal and hydraulic efficiency of the duct.