Basic studies of Multiple Jets and Wall Jets.
Status Rept. Jul 79-Aug 80,
STANFORD UNIV CA JOINT INST OF AERONAUTICS AND ACOUSTICS
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An experimental investigation of the flow field of an underexpanded rectangular jet issuing from a rectangular nozzle of aspect ratio 16.7 was undertaken. Tests were conducted for pressure ratios settling chamber pressureambient pressure ranging from 1.6 to 5.8. For pressure ratios greater than 1.9 the spectrum of the hot wire and microphone signals placed in the near field of the jet show discrete frequencies generally known as screech tones. At a pressure ratio of 3.7, Schlieren pictures show a distinct double wave pattern with their source bing located at about 6 widths downstream. This results in an enhanced spreading of the jet as compared with other pressure ratios. A series of experiments on unconfined multiple jets has been performed for pressure ratios ranging from 1.6 to 3.7. Schlieren pictures were obtained which shows that the individual jets do not attract each other and mixing with the ambient air or secondary air takes place quite independently. The importance of sound waves generated in one of the jets acting upon the neighboring jets is demonstrated. Using this technique, it is shown that the mixing can be enhanced. Author
- Fluid Mechanics