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The fluid dynamics of microflows has recently commanded considerable attention because of their potential applications. Until
now, with a few exceptions, most of the studies have been limited to low speed flows. This experimental study examines supersonic
microjets of 100–1,000 μm in size with exit velocities in the range of 300–500 m/s. Such microjets are presently being used
to actively control larger supersonic impinging jets, which occur in STOVL (short takeoff and vertical landing) aircraft,
cavity flows, and flow separation. Flow properties of free as well as impinging supersonic microjets have been experimentally
investigated over a range of geometric and flow parameters. The flowfield is visualized using a micro-schlieren system with
a high magnification. These schlieren images clearly show the characteristic shock cell structure typically observed in larger
supersonic jets. Quantitative measurements of the jet decay and spreading rates as well as shock cell spacing are obtained
using micro-pitot probe surveys. In general, the mean flow features of free microjets are similar to larger supersonic jets
operating at higher Reynolds numbers. However, some differences are also observed, most likely due to pronounced viscous effects
associated with jets at these small scales. Limited studies of impinging microjets were also conducted. They reveal that,
similar to the behavior of free microjets, the flow structure of impinging microjets strongly resembles that of larger supersonic
impinging jets. 相似文献
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