Experimental study of the unsteady structure of a confined bubble plume

Rensen, Judith; Roig, Véronique

doi:10.1016/s0301-9322(01)00012-x

Cited by 69 publications

(46 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The uncertainty in the longitudinal velocity component v x is estimated at about 4% and in the secondary flow velocities (v y , v z ) at about 10% (Blanckaert 2010). Wandering (periodic oscillations) of bubble plumes with oscillation frequencies from 0.002-0.003 Hz (García and García 2006) to 0.1-0.2 Hz (Rensen and Roig 2001) have been observed in previous investigations. No wandering of the bubble screen was observed in the research reported in this paper.…”

Section: Velocity Measurementssupporting

confidence: 60%

Influencing Flow Patterns and Bed Morphology in Open Channels and Rivers by Means of an Air-Bubble Screen

et al. 2015

View full text Add to dashboard Cite

The ability of a bubble screen to redistribute the flow field and bed morphology in shallow rivers and open channels has been investigated in laboratory experiments. Rising air bubbles generated by a pressurized porous tube situated on the bed induced secondary flow perpendicular to the porous tube. The secondary flow redistributed the longitudinal velocity, which caused also morphological redistribution under mobile-bed conditions. The strength and size of the bubble-induced secondary flow were independent of the base flow velocity and increased with water depth. The size of the secondary flow cell ranged from 3× (immobile bed) to 7× (mobile bed) the water depth. Similar sizes of bubble-induced secondary flow cells have been reported in literature for water depths ranging from 0.1 to 5 m, indicating that the laboratory experiments are relevant for natural rivers and open channels. A mutually strengthening interplay occurred between the bubble screen, the bubble-induced secondary flow, and the morphology. The bubble-induced secondary flow considerably increased the rising velocity of the air bubbles, which on its turn strengthened the secondary flow. The morphological redistribution increased the flow depth in the region covered by the secondary flow cell, which on its turn increased the size and strength of the secondary flow cell, and its effect on the morphological redistribution. This coupled hydrodynamic-morphologic behavior explains the larger size and strength of the secondary flow over a mobile bed than over a flat immobile bed. The results demonstrate the potential of the bubble screen as a technique to modify the morphology in a variety of applications in shallow rivers and open channels.

show abstract

Section: Velocity Measurementssupporting

confidence: 60%

Influencing Flow Patterns and Bed Morphology in Open Channels and Rivers by Means of an Air-Bubble Screen

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Vale ressaltar ainda que a Equação 4 assume que as interações entre as bolhas devido à presença de múltiplos orifícios são desprezíveis, uma vez que a vazão por orifícios Q/n é utilizada no lugar da vazão Q. dos orifícios. Combinando os resultados experimentais aqui obtidos com aqueles disponíveis na literatura (LEITCH & BAINES, 1989;IGUCHI et al, 1995;RENSEN & ROIG, 2001;LIMA NETO et al, 2008a) foi possível obter a seguinte relação adimensional baseada na equação 4:…”

Section: Methodsunclassified

“…A aeração por ar difuso está presente em várias aplicações das engenharias sanitária e ambiental, incluindo desde o tratamento de água/ esgoto ao controle da eutrofização de corpos hídricos (VON SPERLING, 1996a, 1996bRENSEN;ROIG, 2001;SOCOLOFSKY et al, 2002;ZAMBON et al, 2003;MORUZZI & REALI, 2007;LIMA NETO et al, 2008a, 2008c. Nesses tipos de sistemas torna-se importante determinar o tamanho das bolhas geradas, de forma que a hidrodinâmica e os processos de transferência de massa envolvidos possam ser modelados com precisão (WÜEST et al, 1992;MCGINNIS & LITTLE, 2002;LIMA NETO, 2012a, 2012b.…”

Section: Introductionunclassified

Tamanho de bolhas de ar formadas por difusores não porosos na água

Neto

2015

Eng. Sanit. Ambient.

View full text Add to dashboard Cite

RESUMONeste estudo foram realizados experimentos para investigar o tamanho de bolhas de ar formadas a partir de difusores não porosos em um tanque de água.O tamanho das bolhas individuais e o diâmetro de Sauter foram avaliados usando uma técnica de processamento de imagens. Os resultados confirmam que a vazão de ar e o diâmetro do orifício são parâmetros importantes que controlam a distribuição do tamanho das bolhas e o diâmetro de Sauter.Análise dimensional é realizada para fornecer uma relação adimensional geral para predição do diâmetro de Sauter (usando uma escala de comprimento adequada, baseada na vazão de ar) e o número de Reynolds na saída do orifício. Essa relação apresenta bom ajuste aos dados experimentais obtidos neste estudo e a partir de investigações anteriores disponíveis na literatura, incluindo também experimentos com múltiplos orifícios. Finalmente, são apresentadas aplicações potenciais da relação adimensional obtida.Palavras-chave: análise dimensional; bolhas; diâmetro de Sauter; processamento de imagens; plumas.

show abstract

“…by Kobus 1968 andMilgram 1983) produced the basic understanding about their global behaviour. More recent detailed bubbly flow experiments (Hassan et al 1992;Delnoj et al 1999;Kubasch 2001;Rensen & Roig 2001;Simiano et al 2006) were conducted with confined flows or bubble columns. Various effects including recirculation in the vessel and the presence of walls can make the plume centreline and boundaries oscillate in three dimensions.…”

Section: Introductionmentioning

confidence: 99%

Turbulent transport mechanisms in oscillating bubble plumes

et al. 2009

View full text Add to dashboard Cite

The detailed investigation of an unstable meandering bubble plume created in a 2-m-diameter vessel with a water depth of 1.5 m is reported for void fractions up to 4% and bubble size of the order of 2.5 mm. Simultaneous particle image velocity (PIV) measurements of bubble and liquid velocities and video recordings of the projection of the plume on two vertical perpendicular planes were produced in order to characterize the state of the plume by the location of its centreline and its equivalent diameter. The data were conditionally ensemble averaged using only PIV sets corresponding to plume states in a range as narrow as possible, separating the small-scale fluctuations of the flow from the large-scale motions, namely plume meandering and instantaneous cross-sectional area fluctuations. Meandering produces an apparent spreading of the average plume velocity and void fraction profiles that were shown to remain self-similar in the instantaneous plume cross-section. Differences between the true local time-average relative velocities and the difference of the averaged phase velocities were measured; the complex variation of the relative velocity was explained by the effects of passing vortices and by the fact that the bubbles do not reach an equilibrium velocity as they migrate radially, producing momentum exchanges between high- and low-velocity regions. Local entrainment effects decrease with larger plume diameters, contradicting the classical dependence of entrainment on the time-averaged plume diameter. Small plume diameters tend to trigger ‘entrainment eddies’ that promote the inward-flow motion. The global turbulent kinetic energy was found to be dominated by the vertical stresses. Conditional averages according to the plume diameter showed that the large-scale motions did not affect the instantaneous turbulent kinetic energy distribution in the plume, suggesting that large scales and small scales are not correlated. With conditional averaging, meandering was a minor effect on the global kinetic energy and the Reynolds stresses. In contrast, plume diameter fluctuations produce a substantial effect on these quantities.

show abstract

Experimental study of the unsteady structure of a confined bubble plume

Cited by 69 publications

References 19 publications

Influencing Flow Patterns and Bed Morphology in Open Channels and Rivers by Means of an Air-Bubble Screen

Influencing Flow Patterns and Bed Morphology in Open Channels and Rivers by Means of an Air-Bubble Screen

Tamanho de bolhas de ar formadas por difusores não porosos na água

Turbulent transport mechanisms in oscillating bubble plumes

Contact Info

Product

Resources

About