ABSTRACT
The streamwise and the spanwise velocity time series are measured from the wall to the centre of the cross duct for the flow in a rectangular T-junction duct, which is similar to airflow conditions of high-speed train ventilation system. The turbulent statistical properties are reported at three streamwise locations which correspond to the upstream/downstream and the centreline of the T-junction (x/D = ±1 and 0, respectively). Turbulence intensities, skewness and flatness factor, as well as probability density functions, have been investigated at the range of Reτ = 5400–8700. Furthermore, the multiscale properties of the flatness factor are analysed by using orthogonal wavelet transform. It is found that the turbulent intensities remain a constant in the centre region for three streamwise locations while they are weakened in the turbulent boundary layer at x/D = 1 by effect of suction. The location of the strongest intermittency is located at y/h = 0.56 for x/D = −1 and 0. While at downstream of T-junction (x/D = 1), the location of the strongest intermittency shifts down to y/h = 0.28. Also, the wavelet flatness factor is more clearly distinguished the intermittency of the small-scale turbulent structure compared with the conventional flatness factor and, the obtained experimental data are fitted and used to predict the mean streamwise velocity profiles.
Disclosure statement
No potential conflict of interest was reported by the authors.