Supersonic mixing enhanced by cavity-induced three-dimensional oscillatory flow

Abstract

In this study, a novel wall-mounted cavity having a three-dimensional shape is proposed for enhancing supersonic mixing. This device induces an oscillatory secondary flow that effectively enhances mixing. To demonstrate the device performance, we experimentally compare supersonic mixing fields in three ducts without any devices, with a rectangular cavity, and with the newly proposed cavity (new device). In the experiments, time-dependent pressure measurements and oil-flow surface visualization are carried out. The experimental results show that the newly proposed cavity induces not only self-sustained flow oscillation but also secondary flow, both of which effectively enhance mixing. The jet issuing from the injector is also visualized for each duct by a planar laser-induced fluorescence (PLIF) technique. The PLIF visualizations reveal that mixing is enhanced far more rapidly in the duct with the newly proposed cavity than in the other ducts and that the jet penetration in the duct with the newly proposed cavity is much higher. These results are attributed to the large-amplitude jet fluctuation due to the oscillatory secondary flows induced by the newly proposed cavity.