This paper describes an experimental investigation on the normal and oblique subsonic and underexpanded jet impingement. The shadowgraph pictures of normal and oblique impingement show that the stand-off shock at the wall remains parallel to the nozzle exit plane when the wall is moved away from the nozzle exit. The jet field is investigated based on the field characteristics such as spread, wall half-pressure width and wall pressure similarity. The jet spread is strongly influenced by obliqueness of the wall, whereas the wall pressure similarity is independent of obliqueness. The positive pressure zone at the center of impingement planes disappears for a wall at 10 times nozzle exit diameter for subsonic impingement, whereas for underexpanded it disappears as early as 4 times the nozzle exit diameter.
This paper presents the results of an experimental investigation on the free and bounded shear flows. The results show that it is possible to obtain similarity of the free and bounded shear flows with appropriate scales. It is shown that there exists a single relation for length scale to result in complete similarity of the free jet field right from the nozzle exit. The length scale proposed is found to be independent of Reynolds and Mach numbers. The similarity profile of free jet exhibits normaldistribution, whereas bounded shear flow follows a fifth order polynomial variation. It is also shown that a pressure scale can be identified to obtain similarity. The proposed similarity scales for free and bounded shear flows are shown to result in similarity for the combination of free and bounded shear flows also.
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