Near-field Development of Gas-phase Horizontal Laminar Jets with Positive and Negative Buoyancy Measured with Filtered Rayleigh Scattering
Document Type
Article
Publication Date
6-2011
Abstract
Near-field mixing characteristics of horizontally issuing jets, alternatively positively and negatively buoyant, are explored. The cross-sectional mass fraction of a buoyant horizontal jet consisting of helium flowing into ambient air is measured using a non-intrusive technique, filtered Rayleigh scattering, for Reynolds numbers ranging from 50 to 1,200, Froude numbers ranging as low as 0.71, and Schmidt numbers on the order of unity for all tests. Several corresponding experiments were carried out using carbon dioxide in place of helium in order to determine whether the direction of the buoyancy changes the characteristic shape of the jet cross-section. Consistent with the literature, mixing rates were consistently higher on the side of the jet where instability, due to density stratification, was present. At jet Froude numbers ranging between 1.5 and approximately 3, the jet cross-section takes a shape consistent with a single plume of fluid being ejected from the core in a vertical direction-upward for a jet with positive buoyancy and downward for a jet with negative buoyancy. Remarkably, for Froude numbers less than unity, the distortion of the jet is quite different in that two separate plumes emanate from each side of the jet while ejection from the center is suppressed. Both the positively and negatively buoyant jet cross-sections exhibited this trait, suggesting that the mechanism that determines the cross-sectional shape of the jet core is only mildly influenced by centripetal effects brought about by streamline curvature. The location of the jet centroid at varied streamwise locations was computed from the mass fraction data, yielding jet trajectory. Abstract © Springer-Verlag (outside the USA)
DOI
10.1007/s00348-010-0999-5
Source Publication
Experiments in Fluids
Recommended Citation
Reeder, M.F., Huffman, R.E., Branam, R.D. et al. Near-field development of gas-phase horizontal laminar jets with positive and negative buoyancy measured with filtered Rayleigh scattering. Exp Fluids 50, 1455–1472 (2011). https://doi.org/10.1007/s00348-010-0999-5
Comments
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