Hydrodynamics of pulsed supersonic underexpanded jets: Spatiotemporal characteristics |
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Authors: | N G Korobeishchikov A E Zarvin V Zh Madirbaev |
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Institution: | (1) Novosibirsk State University, Novosibirsk, 630090, Russia |
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Abstract: | The gasdynamic parameters of nonsteady expansion of He, Ar, N2, and SiH4 from a sonic nozzle into a space with reduced background gas pressure were experimentally studied for moderate values of
n (103–106) and the Reynolds number (ReL∼100–102). The jet set times necessary for the formation of pulsed jets of a given finite duration are determined. The results are
generalized in terms of dimensionless similarity parameters. The laws of motion of the leading and trailing fronts in pulsed
jets of various gases are established. The leading front of a pulsed jet propagates at a velocity significantly smaller than
the limiting steady value. The jet expansion dynamics is determined by the ratio of the momentum of the expanding gas to that
of the background gas displaced from the flow region. The length of the steady flow region in a pulsed jet monotonically decreases
downstream from the source and drops with increasing background gas pressure because of the loss of jet particles in the trailing
rarefaction wave; this length increases with the initial momentum because the background gas is more intensively displaced
from the flow region. |
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Keywords: | |
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