Fuel-air mixing by cavity-induced acoustic oscillations in confined supersonic flows

An experimental investigation on cold flow mixing of a transverse jet injected into an air stream at Mach 1.5 assisted by cavity-induced acoustic oscillations has been conducted. Acoustic pressure measurements were performed along the wall of the test-section opposite to the cavity, without and with injection of transverse jet for various cavity dimensions. It was observed that the mode shifts of the cavity oscillations is a strong function of depth and these occurred for cavity length to depth (L/D) ratios of 1 and 1.5 approximately. The maximum amplitudes for the modes occurred at L/D = 0.5 and 2. When a transverse jet was injected in front of the cavity, the oscillations were suppressed more for deep cavities than for shallow cavities. Mie scattering technique was adopted to study the mixing behavior of the transversely injected flow in the main flow. Cavity dimensions for these tests were selected based on the acoustic amplitudes registered by flow past the cavities. The results show a slight improvement in mixing of the jet in presence of the cavity, for the dimensions selected for testing in this study. © 2003 by Dr. S. R. Chakravarthy.