Effect of Expansion Ramp Angle on Supersonic Mixing using Streamwise Vortices

For supersonic mixing enhancement, the use of large scale streamwise vortices is the most advantageous. The present study investigates flow charactorestics of mixing region and breakdown process of streamwise vortices, which is produced by expansion ramp and backward facing step, by using schlieren visualization and 3D -PIV. The expansion ramp angle is changed to vary the circulation of streamwise vortices. The results show that circulation of streamwise vortex, distance between streamwise vortices, and velocity difference between free-stream and inside of streamwise vortices have an effect on the expansion ratio of mixing region and breakdown process of streamwise vortices. It is found that there is the suitable expansion ramp angle to expand the mixing region widely. And, it is clarified that the lateral vortex ring surroundi ng streamwise vortices play an important role on the breakdown process of the streamwise vortices.