Front dynamics and macroscopic diffusion in buoyant mixing in a tilted tube

Séon, Thomas; Znaien, J.; Perrin, Bernard; Hinch, E. J.; Salin, D.; Hulin, Jean-Pierre

doi:10.1063/1.2821733

Cited by 53 publications

(28 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a first approach it may be characterized from the streamwise variation of the local average ͗c͑x , t͒͘ y,z of the concentration. 12 This variation takes place over characteristic distances and large times compared to those associated with the local turbulent fluctuations. In order to understand quantitatively this variation as well as that of ͗c͘ as a function of z, we will need to consider the transport mechanisms of concentration within a tube cross section, especially those involving the correlation of velocity and concentration fluctuations.…”

Section: -9mentioning

confidence: 99%

“…1͒. Previous studies of the subsequent interpenetration of the two fluids in the same configuration analyzed macroscopic parameters such as the velocity V f of the displacement fronts 7,12 or the axial profile of the mean concentration. For instance, the variation of V f with the control parameters of the flow displays nontrivial features in the turbulent mixing regime: V f increases both with the viscosity and the tilt angle while it is almost independent of the density contrast and decreases when the tube diameter increases.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and numerical investigations of flow structure and momentum transport in a turbulent buoyancy-driven flow inside a tilted tube

et al. 2009

Self Cite

View full text Add to dashboard Cite

Buoyancy-driven turbulent mixing of fluids of slightly different densities [At=Δρ/(2⟨ρ⟩)=1.15×10−2] in a long circular tube tilted at an angle θ=15° from the vertical is studied at the local scale, both experimentally from particle image velocimetry and laser induced fluorescence measurements in the vertical diametrical plane and numerically throughout the tube using direct numerical simulation. In a given cross section of the tube, the axial mean velocity and the mean concentration both vary linearly with the crosswise distance z from the tube axis in the central 70% of the diameter. A small crosswise velocity component is detected in the measurement plane and is found to result from a four-cell mean secondary flow associated with a nonzero streamwise component of the vorticity. In the central region of the tube cross section, the intensities of the three turbulent velocity fluctuations are found to be strongly different, that of the streamwise fluctuation being more than twice larger than that of the spanwise fluctuation which itself is about 50% larger than that of the crosswise fluctuation. This marked anisotropy indicates that the turbulent structure is close to that observed in homogeneous turbulent shear flows. Still in the central region, the turbulent shear stress dominates over the viscous stress and reaches a maximum on the tube axis. Its crosswise variation is approximately accounted for by a mixing length whose value is about one-tenth of the tube diameter. The momentum exchange in the core of the cross section takes place between its lower and higher density parts and there is no net momentum exchange between the core and the near-wall regions. A sizable part of this transfer is due both to the mean secondary flow and to the spanwise turbulent shear stress. Near-wall regions located beyond the location of the extrema of the axial velocity (|z|≳0.36 d) are dominated by viscous stresses which transfer momentum toward (from) the wall near the top (bottom) of the tube.

show abstract

Section: -9mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigations of flow structure and momentum transport in a turbulent buoyancy-driven flow inside a tilted tube

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…EvidentlyV t andV ∫ represent velocities at which buoyancy is balanced by inertial and viscous forces, respectively. The novelty of our work with respect to Seon et al (2004Seon et al ( , 2005Seon et al ( , 2006Seon et al ( , 2007a is the study of imposed displacement velocities,V 0 > 0. Preliminary results of our study were reported in Taghavi et al (2010).…”

Section: Introductionmentioning

confidence: 99%

“…Exchange flow in an inclined pipe (imposed mean flow velocity,V 0 = 0) has been extensively studied by Seon et al (2004Seon et al ( , 2005Seon et al ( , 2006Seon et al ( , 2007a, also considering iso-viscous fluids and low At. Seon et al (2005) classify exchange flows phenomenologically as either inertial or viscous according to which eAEect is dominant in balancing buoyancy forces, and we adopt the same terminology.…”

Section: Introductionmentioning

confidence: 99%

Miscible displacement flows in near-horizontal ducts at low Atwood number

et al. 2012

View full text Add to dashboard Cite

We study buoyant displacement flows with two miscible fluids of equal viscosity in the regime of low Atwood number and in ducts that are inclined close to horizontal. Using a combination of experimental, computational and analytical methods, we characterize the transitions in the flow regimes between inertial- and viscous-dominated regimes, and as the displacement flow rate is gradually increased. Three dimensionless groups largely describe these flows: densimetric Froude number $\mathit{Fr}$, Reynolds number $\mathit{Re}$ and duct inclination $\ensuremath{\beta} $. Our results show that the flow regimes collapse into regions in a two-dimensional $(\mathit{Fr}, \mathit{Re}\cos \ensuremath{\beta} / \mathit{Fr})$ plane. These regions are qualitatively similar between pipes and plane channels, although viscous effects are more extensive in pipes. In each regime, we are able to give a leading-order estimate for the velocity of the leading displacement front, which is effectively a measure of displacement efficiency.

show abstract

“…A typical system studied involves two, initially stratified, miscible fluids of different densities in vertical and tilted tubes, with the more dense fluid overlying the less dense one [46][47][48][49][50]. The velocity of the leading edge of the inter-penetration zone, and the axial and temporal evolution of the mean relative concentration are measured as a function of tilt angle for a given set of fluid physical properties.…”

Section: Introductionmentioning

confidence: 99%

Pressure-driven miscible two-fluid channel flow with density gradients

et al. 2009

View full text Add to dashboard Cite

We study the effect of buoyancy on pressure-driven flow of two miscible fluids in inclined channels via direct numerical simulations. The flow dynamics are governed by the continuity and NavierStokes equations, without the Boussinesq approximation, coupled to a convective-diffusion equation for the concentration of the more viscous fluid through a concentration-dependent viscosity and density. The effect of varying the density ratio, Froude number, and channel inclination on the flow dynamics is examined, for moderate Reynolds numbers. We present results showing the spatio-temporal evolution of the flow together with an integral measure of mixing. *

show abstract

Front dynamics and macroscopic diffusion in buoyant mixing in a tilted tube

Cited by 53 publications

References 21 publications

Experimental and numerical investigations of flow structure and momentum transport in a turbulent buoyancy-driven flow inside a tilted tube

Experimental and numerical investigations of flow structure and momentum transport in a turbulent buoyancy-driven flow inside a tilted tube

Miscible displacement flows in near-horizontal ducts at low Atwood number

Pressure-driven miscible two-fluid channel flow with density gradients

Contact Info

Product

Resources

About