On the entrainment coefficient in negatively buoyant jets

Papanicolaou, PN; Papakonstantis, IG; Christodoulou, GC

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