Effects of nozzle-exit boundary-layer conditions on excitability of heated free jetsThis paper reports an experimental study on the effects of nozzle-exit boundary-layer conditions on the excitability of heated free jets. The results were obtained at a Mach number 0.8 and total temperatures of 300 K and 670 K. External acoustic excitation was used to excite the jet. The excitation frequencies ranged up to 6 KHZ and the excitation levels were up to 150 dB. A level of 147 dB was used for most of the test points. Nozzle-exit boundary-layer characteristics were controlled by boundary layer tripping upstream of the nozzle exit plane. It has been shown that the free jet mixing rate strongly depends on the boundary-layer characteristics at the nozzle exit. Further, it appears that jets with a thin laminar nozzle-exit boundary layer are more selective about the optimum excitation frequency than those with a thick turbulent nozzle-exit boundary layer. Finally, for the jet of Mach number 0.8, it appears that free jet mixing and development may be controlled by flow excitation as well as by nozzle-exit boundary-layer modifications.
Document ID
19880032955
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Lepicovsky, J. (Lockheed-Georgia Co. Marietta, GA, United States)
Brown, W. H. (Lockheed Aeronautical Systems Co. Georgia Div., Marietta, United States)