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On the entrainment coefficient in negatively buoyant jets

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dc.contributor.author Papanicolaou, PN en
dc.contributor.author Papakonstantis, IG en
dc.contributor.author Christodoulou, GC en
dc.date.accessioned 2014-03-01T01:28:56Z
dc.date.available 2014-03-01T01:28:56Z
dc.date.issued 2008 en
dc.identifier.issn 0022-1120 en
dc.identifier.uri https://dspace.lib.ntua.gr/xmlui/handle/123456789/19035
dc.subject.classification Mechanics en
dc.subject.classification Physics, Fluids & Plasmas en
dc.subject.other Buoyancy en
dc.subject.other Concentration (process) en
dc.subject.other Trellis codes en
dc.subject.other Asymptotic values en
dc.subject.other Buoyant jets en
dc.subject.other Dilution rates en
dc.subject.other Entrainment coefficients en
dc.subject.other Experimental datum en
dc.subject.other Flow regimes en
dc.subject.other Gaussian en
dc.subject.other Gaussian distribution models en
dc.subject.other Geometrical characteristics en
dc.subject.other Integral models en
dc.subject.other Jets and plumes en
dc.subject.other Model predictions en
dc.subject.other Richardson numbers en
dc.subject.other Self-similarity en
dc.subject.other Steady states en
dc.subject.other Stratified environments en
dc.subject.other Stratified fluids en
dc.subject.other Top hatted en
dc.subject.other Jets en
dc.subject.other buoyancy en
dc.subject.other entrainment en
dc.subject.other flow modeling en
dc.subject.other Gaussian method en
dc.subject.other jet en
dc.subject.other Richardson number en
dc.title On the entrainment coefficient in negatively buoyant jets en
heal.type journalArticle en
heal.identifier.primary 10.1017/S0022112008003509 en
heal.identifier.secondary http://dx.doi.org/10.1017/S0022112008003509 en
heal.language English en
heal.publicationDate 2008 en
heal.abstract Integral models proposed to simulate positively buoyant jets are used to model jets with negative or reversing buoyancy issuing into a calm, homogeneous or density-stratified environment. On the basis of the self-similarity assumption, 'top hat' and Gaussian cross-sectional distributions are employed for concentration and velocity. The entrainment coefficient is considered to vary with the local Richardson number, between the asymptotic values for simple jets and plumes, estimated from earlier experiments in positively buoyant jets. Top-hat and Gaussian distribution models are employed in a wide range of experimental data on negatively buoyant jets, issuing vertically or at an angle into a calm homogeneous ambient, and on jets with reversing buoyancy, discharging into a calm, density-stratified fluid. It is found that geometrical characteristics such as the terminal (steady state) height of rise, the spreading elevation in stratified ambient and the distance to the point of impingement are considerably underestimated, resulting in lower dilution rates at the point of impingement, especially when the Gaussian formulation is applied. Reduction of the entrainment coefficient in the jet-like flow regime improves model predictions, indicating that the negative buoyancy reduces the entrainment in momentum-driven, negatively buoyant jets. © 2008 Cambridge University Press. en
heal.publisher CAMBRIDGE UNIV PRESS en
heal.journalName Journal of Fluid Mechanics en
dc.identifier.doi 10.1017/S0022112008003509 en
dc.identifier.isi ISI:000260940300020 en
dc.identifier.volume 614 en
dc.identifier.spage 447 en
dc.identifier.epage 470 en


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