Mixing in Circular and Non-circular Jets in Crossflow |
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Authors: | M Salewski D Stankovic L Fuchs |
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Institution: | (1) Div. Fluid Mechanics, Lund University, 221 00 Lund, Sweden |
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Abstract: | Coherent structures and mixing in the flow field of a jet in crossflow have been studied using computational (large eddy simulation)
and experimental (particle image velocimetry and laser-induced fluorescence) techniques. The mean scalar fields and turbulence
statistics as determined by both are compared for circular, elliptic, and square nozzles. For the latter configurations, effects
of orientation are considered. The computations reveal that the distribution of a passive scalar in a cross-sectional plane
can be single- or double-peaked, depending on the nozzle shape and orientation. A proper orthogonal decomposition of the transverse
velocity indicates that coherent structures may be responsible for this phenomenon. Nozzles which have a single-peaked distribution
have stronger modes in transverse direction. The global mixing performance is superior for these nozzle types. This is the
case for the blunt square nozzle and for the elliptic nozzle with high aspect ratio. It is further demonstrated that the flow
field contains large regions in which a passive scalar is transported up the mean gradient (counter-gradient transport) which
implies failure of the gradient diffusion hypothesis. |
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Keywords: | Jet in crossflow Mixing Coherent structures Transverse jet Nozzle shape |
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