TY - CONF
T1 - Enhancement of large scale structures in supersonic axisymmetric jets using laser excitation
AU - Elliott, Gregory S.
AU - Crawford, Jason
AU - Mosedale, Andrew
N1 - Funding Information:
support of the National Science Foundation, grant number NSF-9622108 with Dr. R. Arndt, AFOSR 1997 SREP with Dr. Mark Gruber, and the Rutgers Research Council Grant. Also the assistance of the technicians and graduate students at Rutgers University is very much appreciated.
Publisher Copyright:
© 1998 by Gregory S. Elliott.
PY - 1998
Y1 - 1998
N2 - A creative method of controlling and forcing supersonic mixing layers has been demonstrated. A laser beam from a frequency-doubled pulsed Nd:YAG laser is focused at the nozzle exit of an axisymmetric jet. Pulsing the laser causes a thermal peak at the jet surface, forcing the shear layer where it is formed. Preliminary measurements show that this is an effective means to enhance and control the large scale structures formed at the exit of perfectly expanded jets with Mach numbers of 1.36, 1.5, and 2. The convective Mach numbers of these jets are 0.63, 0.68, and 0.85, respectively. Two laser pulses are used: the first excites the flow, and the second, delayed in time and formed into a sheet, interrogates the flow for visualization. The convective velocity of the large scale structures was found to be slightly higher than predicted theoretically. Since the formation of the large scale structures can be controlled, high frequency pressure measurements were made simultaneously with each instantaneous image. The pressure trace indicates the lower and higher pressures associated with the vortex core and braid regions of the large scale structures, respectively. The laser excitation technique provides a unique opportunity to study the spatially stable large scale structures and a novel method for enhancing the growth rate of a supersonic shear layer.
AB - A creative method of controlling and forcing supersonic mixing layers has been demonstrated. A laser beam from a frequency-doubled pulsed Nd:YAG laser is focused at the nozzle exit of an axisymmetric jet. Pulsing the laser causes a thermal peak at the jet surface, forcing the shear layer where it is formed. Preliminary measurements show that this is an effective means to enhance and control the large scale structures formed at the exit of perfectly expanded jets with Mach numbers of 1.36, 1.5, and 2. The convective Mach numbers of these jets are 0.63, 0.68, and 0.85, respectively. Two laser pulses are used: the first excites the flow, and the second, delayed in time and formed into a sheet, interrogates the flow for visualization. The convective velocity of the large scale structures was found to be slightly higher than predicted theoretically. Since the formation of the large scale structures can be controlled, high frequency pressure measurements were made simultaneously with each instantaneous image. The pressure trace indicates the lower and higher pressures associated with the vortex core and braid regions of the large scale structures, respectively. The laser excitation technique provides a unique opportunity to study the spatially stable large scale structures and a novel method for enhancing the growth rate of a supersonic shear layer.
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U2 - 10.2514/6.1998-331
DO - 10.2514/6.1998-331
M3 - Paper
AN - SCOPUS:85086949250
T2 - 36th AIAA Aerospace Sciences Meeting and Exhibit, 1998
Y2 - 12 January 1998 through 15 January 1998
ER -