Unsteady propagation of a liquid plug in a liquid-lined straight tube

Fujioka, Hideki; Takayama, Shuichi; Grotberg, James B.

doi:10.1063/1.2938381

Cited by 52 publications

(81 citation statements)

References 47 publications

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“…Finally, when the length of the plug approaches zero, it ruptures. A similar behavior has been observed by Fujioka et al (34) through direct numerical simulations of the flow field inside a moving plug.…”

supporting

confidence: 64%

Airway reopening through catastrophic events in a hierarchical network

Baudoin

Song

Manneville

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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When you reach with your straw for the final drops of a milkshake, the liquid forms a train of plugs that flow slowly initially because of the high viscosity. They then suddenly rupture and are replaced with a rapid airflow with the characteristic slurping sound. Trains of liquid plugs also are observed in complex geometries, such as porous media during petroleum extraction, in microfluidic two-phase flows, or in flows in the pulmonary airway tree under pathological conditions. The dynamics of rupture events in these geometries play the dominant role in the spatial distribution of the flow and in determining how much of the medium remains occluded. Here we show that the flow of a train of plugs in a straight channel is always unstable to breaking through a cascade of ruptures. Collective effects considerably modify the rupture dynamics of plug trains: Interactions among nearest neighbors take place through the wetting films and slow down the cascade, whereas global interactions, through the total resistance to flow of the train, accelerate the dynamics after each plug rupture. In a branching tree of microchannels, similar cascades occur along paths that connect the input to a particular output. This divides the initial tree into several independent subnetworks, which then evolve independently of one another. The spatiotemporal distribution of the cascades is random, owing to strong sensitivity to the plug divisions at the bifurcations. microfluidics | respiratory flow T he motion of liquid plugs through a connected network of channels may involve many degrees of freedom evolving via a similarly large number of interactions: each immiscible interface introduces a degree of freedom into the problem owing to its ability to deform and to move, whereas each connecting branch between different areas introduces an interaction path that allows the flow in one region to influence the behavior in other areas of the network. The resulting flow pattern determines, among other things, how water or oil is extracted from porous media (1-3), the imbibition of paper (4, 5), and the stability of flow in a microfluidic device (6, 7).Liquid-gas two-phase flows also occur in the pulmonary airway tree, which is constantly coated with a thin liquid film. When the thickness of this film increases beyond some limit, plugs of liquid may form (8, 9) and therefore occlude the flow of air to the distal branches. Evidence of such behavior has been observed in pathologies ranging from asthma (10, 11) to cystic fibrosis (12). Furthermore, liquid plugs may be used as means to deliver medical treatment into the lung, e.g., in surfactant replacement therapy (13), and these plugs were observed to go through complex divisions, breaking and reforming before reaching their intended target (14).The structure of the lung as a branching binary tree has motivated many studies on the motion of gas-liquid flows into bifurcating channels (15)(16)(17)(18)(19)(20), with numerical work also taking into account the elasticity of the pulmonary walls, (e.g refs. ...

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supporting

confidence: 64%

Airway reopening through catastrophic events in a hierarchical network

Baudoin

Song

Manneville

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…As can be seen, the lubrication theory model agrees very well with the direct numerical simulation, which was obtained by solving the Navier-Stokes equations and boundary conditions using a finite volume method. 39 All the parameters in the finite volume simulation were the same as in the lubrication theory model except that unsteady effects were retained. The Ohnesorge number, Oh = s / ͱ a, the ratio of viscous forces to inertial and surface tension forces was large, equal to 10.…”

Section: A Validationmentioning

confidence: 99%

The effect of viscoelasticity on the stability of a pulmonary airway liquid layer

2010

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The lungs consist of a network of bifurcating airways that are lined with a thin liquid film. This film is a bilayer consisting of a mucus layer on top of a periciliary fluid layer. Mucus is a non-Newtonian fluid possessing viscoelastic characteristics. Surface tension induces flows within the layer, which may cause the lung's airways to close due to liquid plug formation if the liquid film is sufficiently thick. The stability of the liquid layer is also influenced by the viscoelastic nature of the liquid, which is modeled using the Oldroyd-B constitutive equation or as a Jeffreys fluid. To examine the role of mucus alone, a single layer of a viscoelastic fluid is considered. A system of nonlinear evolution equations is derived using lubrication theory for the film thickness and the film flow rate. A uniform film is initially perturbed and a normal mode analysis is carried out that shows that the growth rate g for a viscoelastic layer is larger than for a Newtonian fluid with the same viscosity. Closure occurs if the minimum core radius, R min ͑t͒, reaches zero within one breath. Solutions of the nonlinear evolution equations reveal that R min normally decreases to zero faster with increasing relaxation time parameter, the Weissenberg number We. For small values of the dimensionless film thickness parameter , the closure time, t c , increases slightly with We, while for moderate values of , ranging from 14% to 18% of the tube radius, t c decreases rapidly with We provided the solvent viscosity is sufficiently small. Viscoelasticity was found to have little effect for Ͼ0.18, indicating the strong influence of surface tension. The film thickness parameter and the Weissenberg number We also have a significant effect on the maximum shear stress on tube wall, max͑ w ͒, and thus, potentially, an impact on cell damage. Max͑ w ͒ increases with for fixed We, and it decreases with increasing We for small We provided the solvent viscosity parameter is sufficiently small. For large Ϸ 0.2, there is no significant difference between the Newtonian flow case and the large We cases.

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“…2], which mimics liquid plugs in pulmonary airways [14], for simplicity in the analysis of radiation effects.…”

Section: Introductionmentioning

confidence: 99%

“…The undulator gap was set to 31 mm, and most of the beam intensity was confined within the first harmonic at ~13 keV (1 Å wavelength), with a peak irradiance of ~10 14 photons mm -2 s -1 /0.1%bw (equally ~1 ph Å -2 s -1 /0.1%bw), as clearly seen by the energy spectrum from the undulator. The X-ray photons were irradiated into the confined water by this high-brilliance white X-ray beam.…”

mentioning

confidence: 99%

X-ray-induced water vaporization

Weon

Lee

et al. 2011

Phys. Rev. E

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We present quantitative evidence for X-ray-induced water vaporization: water is vaporized at a rate of 5.5 pL/s with the 1-Å-wavelength X-ray irradiation of ~0.1 photons per Å 2 ; moreover, water vapor is reversibly condensed during pauses in irradiation. This result fundamentally suggests that photoionization induces vaporization. This phenomenon is attributed to surface tension reduction by ionization and would be universally important in radiological and electrohydrodynamic situations.PACS numbers: 68.03. Fg, 68.03.Cd, 78.70.-g * E-mail: bmweon@hotmail.com, † jhje@postech.ac.krBrief Report -Physical Review E -2 -X-ray photonics is undergoing a revolution in imaging capabilities with the use of ultrabright X-ray sources. X-ray imaging at the nano-and microscale is of great interest for applications in physical and life sciences, including X-ray physics, materials science, biological imaging, environmental analysis, archaeology, paleontology, and heritage restoration [1], because it facilitates the nondestructive, direct visualization of internal structures or elements.Meanwhile, radiation damage from the energy deposited into the sample by the X-ray photons used for imaging is inevitable [2,3]. In particular, radiation-induced ionization ultimately disintegrates the sample by charge accumulation beyond a limit and is otherwise known as Coulomb explosion [2,3] and fission [4,5]. The conventional damage barrier for Coulomb explosion is known to be about 200 photons per Å 2 for X-rays with a wavelength of 1 Å [2,3].Radiation damage can be mitigated by cryofixation or by ultrabright, ultrashort X-ray pulses [2].However, radiation damage to living tissues by radiation ionization is not yet fully understood[6], although it is a limiting factor in achieving high-resolution data [2].In previous works, we demonstrated that high-brilliance X-ray photons affect the surface tension of water by inducing ionization, using hard X-ray imaging at the 7B2 beamline (dose rate ~1 kGy s -1 ) of the Pohang Light Source [7][8][9]. A charge density over ~10 -4 charges per Å 2 was required for a significant reduction (> 30%) in the surface tension [9]. This condition corresponds to X-ray irradiation of ~0.1 photons per Å 2 , following a simulation using the ionization rate of ~1 charge per Å 2 by 2000 photons per Å 2 with X-rays of 1 Å wavelength [2].We put forward a possibility of water vaporization by surface tension reduction [7,8] based on a monotonic relationship of the surface tension to the vaporization enthalpy [10,11], but quantitative evidence was lacking.To corroborate the possibility, we conducted an elaborate experiment in a different synchrotron source while applying high-speed X-ray imaging [12,13]. Using a hydrophilic capillary tube containing a small amount of water, we first made a confined water lens with concave menisci, where the left region was closed and the right one was open in air [ Fig. 1]. The changes of the water menisci were simultaneously imaged using a high-speed camera, synchronized and gated t...

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Unsteady propagation of a liquid plug in a liquid-lined straight tube

Cited by 52 publications

References 47 publications

Airway reopening through catastrophic events in a hierarchical network

Airway reopening through catastrophic events in a hierarchical network

The effect of viscoelasticity on the stability of a pulmonary airway liquid layer

X-ray-induced water vaporization

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