Abstract: Temperature and velocity fluctuations of hot and cold fluids mixing in horizontal T-junctions are numerically predicted using large-eddy simulation(LES) on FLUENT platform, the main pipe of T-junctions are with the upstream straight and elbow pipes respectively. Comparisons of the numerical results of normalized mean and root-mean square(RMS) temperature and velocity with available experiments are conducted; the numerical results are in good agreement with the experimental data, which shows that the large eddy simulation is not only reliable but also accurate. The simulated normalized mean and root-mean square(RMS) temperature and velocity, velocity vector and temperature contour of the two horizontal tees are compared. The results indicate that, due to the effect of the secondary flow which produced by upstream elbow pipe, the mixing region and the amplitude of temperature and velocity fluctuations of the tee junction with the upstream elbow pipe are larger than those with the upstream straight pipe, which shows that the upstream elbow pipe of the main pipe has significant influence on the mixing resulting in enhancing the temperature and velocity fluctuations.

Key words: horizontal tee junction;mixing;large-eddy simulation