Periodic Excitation for Jet Vectoring and Enhanced SpreadingThe effects of periodic excitation on the evolution of a turbulent jet were studied experimentally. A short, wide-angle diffuser was attached to the jet exit and excitation was introduced at the junction between the jet exit and the diffuser inlet. The introduction of high amplitude periodic excitation at the jet exit enhances the mixing and promotes attachment of the jet shear-layer to the diffuser wall. Vectoring is achieved by applying the excitation over a fraction of the circumference of the circular jet, enhancing its spreading rate on the excited side and its tendency to reattach to that side. Static deflection studies demonstrate that the presence of the wide-angle diffuser increases the effectiveness of the added periodic momentum due to a favorable interaction between the excitation, the jet shear-layer and the diffuser wall. This point was further demonstrated by the evolution of a wave packet that was excited in the jet shear-layer. Strong amplification of the wave packet was measured with a diffuser attached to the jet exit. The turbulent jet responds quickly (10-20 msec) to step changes in the level of the excitation input. The response scales with the jet exit velocity and is independent of the Reynolds number. Jet deflection angles were found to be highly sensitive to the relative direction between the excitation and the jet flow and less sensitive to the excitation frequency. The higher jet deflection angles were obtained for a diffuser length of about two diameters and for diffusers with half-angles greater than 15 degrees.
Document ID
20040086854
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Pack, LaTunia G. (NASA Langley Research Center Hampton, VA, United States)
Seifert, Avi (National Academy of Sciences - National Research Council Hampton, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 1999
Subject Category
Aerodynamics
Report/Patent Number
AIAA Paper 99-0672
Meeting Information
Meeting: 37th AIAA Aerospace Sciences Meeting and Exhibit
Location: Reno, NV
Country: United States
Start Date: January 11, 1999
End Date: January 14, 1999
Sponsors: American Inst. of Aeronautics and Astronautics