Abstract
The promotion of mixing and diffusion in an axisymmetric jet is tried by using multiple prominences: six vortex generators (VGs). The experimental instrument consists of the wind tunnel and the test section. The square jet is issued at the exit of wind tunnel. The circular skimmer of 30mm diameter is placed at the inlet of the test section in order to eliminate boundary layer developed on the inner wall of the wind tunnel contraction. A VG has a right-angled triangle-shaped chip, and it is installed in an angle of 30 degrees from the flow direction. VGs are mounted around the exit of the skimmer and their motions can be controlled independently by computer programming. VGs can impose the disturbances on the turbulent jet. In this study, two moving-modes are tested beside the stationary mode: in the first mode, all the VGs are oscillated radially in phase (axisymmetric mode); and in the second mode, three VGs in the opposite side are put in and out to the main flow region alternately (alternative mode). Next, the experiment in a heated axisymmetric jet is performed where heat is considered as a passive scalar. Simultaneous measurements of the velocity and temperature are performed using a composite probe of I-type Hot-wire and I-type Cold-wire. The results show the axisymmetric mode is the most effective for the promotion of the heat transport in the near-field region of the axisymmetric jet exit.
