Cryogenic High-Pressure Shear-Coaxial Jets Exposed to Transverse Acoustic Forcing
CALIFORNIA UNIV LOS ANGELES DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
Pagination or Media Count:
This experimental study investigated the response of dynamic flow structures of cryogenic coaxial nitrogen jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode PAN. The role of injector exit geometry on the flow response was examined using two shear coaxial injectors with different outer-to-inner jet area ratios. Flow conditions for varying outer-to-inner jet momentum flux ratios 0.5 - 20, and acoustic pressure antinode at the jet axis location, under subcritical reduced pressure of 0.44 chamber pressures were considered. Dark-core length measurements of the dense inner jet were used to indicate the extent of mixing under different flow conditions and exit geometries. A basic application of proper orthogonal decomposition on the intensity fluctuation of high-speed images enabled the extraction of the spatial and temporal characteristics of the dominant flow structures that existed in the flow field during exposure to acoustic forcing. Regardless of injector geometry or pressure regime, low outer-to-inner momentum flux ratio flows were found to be responsive to acoustic pressure antinode forcing. With increasing momentum flux ratio, however, the flow response to forcing depended on the injector geometry.