Large eddy simulation of flow and mixing characteristics in a T-junction under inflow pulsation

•Flow and thermal mixing at different amplitudes and periods have been performed.•The instantaneous mixing temperature and velocity change periodically with time.•The backflow occurs near the moment of t = 3 T/4.•Wavelet analysis of velocity and temperature fluctuations have been conducted. Large eddy simulation is performed to investigate the mixing characteristics between the hot and cold fluids in a T-junction with different amplitudes and periods of inlet velocity. The distributions of temperature field and velocity field as well as the properties of vortex structures are focused in the present study. In addition, the wavelet power spectrum density (WPSD) of both temperature and velocity fluctuations are investigated by wavelet transform. The results show that the instantaneous temperature and velocity in the mixing area vary periodically, while the variation period is the same as that of inlet velocity. A typical phenomenon is observed near the moment of lowest inlet velocity, the backflow occurs near the upstream of the opposite wall of the jet entrance. Moreover, the WPSD results show that both mixing velocity and temperature fluctuations have the identical prominent frequency which is equal to that of inlet velocity. The period of inlet velocity has a large effect on the WPSDs of velocity and temperature fluctuations in the low frequency region, while does the amplitude of inlet velocity in the high frequency region. In addition, the effect of either period or amplitude on velocity fluctuations is not synchronized with that of temperature fluctuations.