Thermal mixing in T-junctions with different incident angle of branch pipe

Abstract

In this paper, a detailed study of mixing characteristics and temperature fluctuations in T-junctions of 90° and 45° is carried out based on visualization experiments and Large Eddy Simulations (LES). In this study, both flow patterns in the T-junctions are wall jets. Unique thermocouples are employed in the experiments to reduce the influence of temperature measurement on the flow field. The LES is validated by the experimental data. The statistical results from LES indicate that the branch flow incidence of 45° makes the mixing uniformity worse. The instantaneous LES results show that the shear layer vortices and quasi Karman vortex series dominate the fluctuations on the thermal stratification interface. The formation and motion of the shear layer vortices depend on the angle of incidence, while the quasi Karman vortex series is almost unaffected. The shear layer vortices in the 90°/45° cases determine the dominant frequency at 5.5 Hz/10 Hz. The dominant frequency of near-wall temperature fluctuations at 3 Hz in both cases is determined by the quasi Karman vortex series.