Flow characteristics in a counter-type mixing tee

We investigated experimentally the unsteady flow in a counter-type T-junction. The T-junction was modeled by a mixing tee with square cross sections, in which the mixing channel was connected with the main and counter channels at right angles. Detailed distribution of velocity data have been measured using PIV. Reynolds number of the main-channel flow was fixed at 3500, and the velocity ratio of the counter-channel flow to main one was changed from 1.0 to 5.0. To identify the coherent flow structures, the proper orthogonal decomposition (POD) analysis was applied to the fluctuating velocity field in the mixing channel. Based on the data, the unsteady vertical motion along the shear layer and the wobbling motion of the interface between the main-channel and counter-channel flows are discussed. (author)