Liquid Plug Flow in Straight and Bifurcating Tubes

2001 ◽  
Vol 123 (6) ◽  
pp. 580-589 ◽  
Author(s):  
K. J. Cassidy ◽  
N. Gavriely ◽  
J. B. Grotberg
Keyword(s):  
Film Thickness ◽  
Finite Length ◽  
Capillary Number ◽  
Plug Flow ◽  
Precursor Film ◽  
Liquid Plug ◽  
Flow Asymmetry ◽  
Surface Liquid ◽  
Airway Walls ◽  
Deposited Film

A finite-length liquid plug may be present in an airway due to disease, airway closure, or by direct instillation for medical therapy. Air forced by ventilation propagates the plug through the airways, where it deposits fluid onto the airway walls. The plug may encounter single or bifurcating airways, an airway surface liquid, and other liquid plugs in nearby airways. In order to understand how these flow situations influence plug transport, benchtop experiments are performed for liquid plug flow in: Case (i) straight dry tubes, Case (ii) straight pre-wetted tubes, Case (iii) bifurcating dry tubes, and Case (iv) bifurcating tubes with a liquid blockage in one daughter. Data are obtained for the trailing film thickness and plug splitting ratio as a function of capillary number and plug volumes. For Case (i), the finite length plug in a dry tube has similar behavior to a semi-infinite plug. For Case (ii), the trailing film thickness is dependent upon the plug capillary number (Ca) and not the precursor film thickness, although the shortening or lengthening of the liquid plug is influenced by the precursor film. For Case (iii), the plug splits evenly between the two daughters and the deposited film thickness depends on the local plug Ca, except for a small discrepancy that may be due to an entrance effect or from curvature of the tubes. For Case (iv), a plug passing from the parent to daughters will deliver more liquid to the unblocked daughter (nearly double, consistently) and then the plug will then travel at greater Ca in the unblocked daughter as the blocked. The flow asymmetry is enhanced for a larger blockage volume and diminished for a larger parent plug volume and parent-Ca.

Splitting of a two-dimensional liquid plug at an airway bifurcation

2016 ◽  
Vol 793 ◽  
pp. 1-20 ◽  
Author(s):  
Benjamin L. Vaughan ◽  
James B. Grotberg
Keyword(s):  
Gravitational Field ◽  
Capillary Number ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Medical Treatments ◽  
Liquid Plug ◽  
Splitting Ratio ◽  
Critical Capillary Number ◽  
Airway Walls ◽  
Airway Bifurcation

Certain medical treatments involve the introduction of exogenous liquids in the lungs. These liquids can form plugs within the airways. The plugs propagate throughout the branching network in the lungs being forced by airflow. They leave a deposited film on the airway walls and split at bifurcations. Understanding the resulting distribution of liquid throughout the lungs is important for the effective administration of the prescribed treatments. In this paper, we investigate numerically the splitting of a liquid plug by a two-dimensional pulmonary bifurcation under the influence of a transverse gravitational field. The splitting is characterized by the splitting ratio, which is the ratio of volume of the liquid plug in the daughter channels and depends on the capillary number and the orientation of the bifurcation plane with respect to a three-dimensional gravitational field. It is observed that gravity induces asymmetry in the splitting, causing the splitting ratio to be reduced. This effect is mitigated as the capillary number is increased. It is also observed that there exists a critical capillary number where the plug will not split and will instead propagate entirely into the gravitationally favoured daughter channel. We also compute the wall stresses on the bifurcation walls and observe the locations where stresses and their gradients are the highest in magnitude.

scholarly journals Thickness-Dependent Swelling Behavior of Vapor-Deposited Hydrogel Thin Films

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 757 ◽  
Author(s):  
Fabian Muralter ◽  
Alberto Perrotta ◽  
Anna Maria Coclite
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Chemical Vapor ◽  
Solution Temperature ◽  
Cross Linking ◽  
Temperature Sensitive ◽  
Critical Solution Temperature ◽  
Precise Control ◽  
Initiated Chemical Vapor Deposition ◽  
Deposited Film

Hydrogel thin films containing temperature sensitive chemical functionalities (such as N-isopropylacrylamide, NIPAAm) are particularly interesting for sensor and actuator setups. Complex 3D structures can be conformally coated by the solvent free technique initiated Chemical Vapor Deposition, with precise control over chemical composition and film thickness. In this study, NIPAAm-based thin films with film thicknesses ranging from tens to several hundreds of nanometers and with different amounts of cross-linking were deposited. Above the lower critical solution temperature (LCST), these films repel out water and hence shrink. The amount of cross-linking and the deposited film thickness were successfully identified to both affect shape and position of the LCST transition of these systems: a promising basis for tuning response properties.

scholarly journals Effects of surfactant on propagation and rupture of a liquid plug in a tube

2019 ◽  
Vol 872 ◽  
pp. 407-437 ◽  
Author(s):  
M. Muradoglu ◽  
F. Romanò ◽  
H. Fujioka ◽  
J. B. Grotberg
Keyword(s):  
Shear Stress ◽  
Evolution Equations ◽  
Stokes Equations ◽  
Thin Liquid Film ◽  
Front Tracking ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Liquid Plug ◽  
Front Tracking Method ◽  
Airway Walls

Surfactant-laden liquid plug propagation and rupture occurring in lower lung airways are studied computationally using a front-tracking method. The plug is driven by an applied constant pressure in a rigid axisymmetric tube whose inner surface is coated by a thin liquid film. The evolution equations of the interfacial and bulk surfactant concentrations coupled with the incompressible Navier–Stokes equations are solved in the front-tracking framework. The numerical method is first validated for a surfactant-free case and the results are found to be in good agreement with the earlier simulations of Fujioka et al. (Phys. Fluids, vol. 20, 2008, 062104) and Hassan et al. (Intl J. Numer. Meth. Fluids, vol. 67, 2011, pp. 1373–1392). Then extensive simulations are performed to investigate the effects of surfactant on the mechanical stresses that could be injurious to epithelial cells, such as pressure and shear stress. It is found that the liquid plug ruptures violently to induce large pressure and shear stress on airway walls and even a tiny amount of surfactant significantly reduces the pressure and shear stress and thus improves cell survivability. However, addition of surfactant also delays the plug rupture and thus airway reopening.

Effect of Gravity on Liquid Plug Transport Through an Airway Bifurcation Model

2005 ◽  
Vol 127 (5) ◽  
pp. 798-806 ◽  
Author(s):  
Y. Zheng ◽  
J. C. Anderson ◽  
V. Suresh ◽  
J. B. Grotberg
Keyword(s):  
Capillary Number ◽  
Axial Direction ◽  
Bond Number ◽  
Liquid Volume ◽  
Liquid Plug ◽  
Splitting Ratio ◽  
Wide Range ◽  
Critical Capillary Number ◽  
Airway Bifurcation ◽  
Parent Tube

Many medical therapies require liquid plugs to be instilled into and delivered throughout the pulmonary airways. Improving these treatments requires a better understanding of how liquid distributes throughout these airways. In this study, gravitational and surface mechanisms determining the distribution of instilled liquids are examined experimentally using a bench-top model of a symmetrically bifurcating airway. A liquid plug was instilled into the parent tube and driven through the bifurcation by a syringe pump. The effect of gravity was adjusted by changing the roll angle (ϕ) and pitch angle (γ) of the bifurcation (ϕ=γ=0deg was isogravitational). ϕ determines the relative gravitational orientation of the two daughter tubes: when ϕ≠0deg, one daughter tube was lower (gravitationally favored) compared to the other. γ determines the component of gravity acting along the axial direction of the parent tube: when γ≠0deg, a nonzero component of gravity acts along the axial direction of the parent tube. A splitting ratio Rs, is defined as the ratio of the liquid volume in the upper daughter to the lower just after plug splitting. We measured the splitting ratio, Rs, as a function of: the parent-tube capillary number (Cap); the Bond number (Bo); ϕ; γ; and the presence of pre-existing plugs initially blocking either daughter tube. A critical capillary number (Cac) was found to exist below which no liquid entered the upper daughter (Rs=0), and above which Rs increased and leveled off with Cap. Cac increased while Rs decreased with increasing ϕ, γ, and Bo for blocked and unblocked cases at a given Cap>Cac. Compared to the nonblockage cases, Rs decreased (increased) at a given Cap while Cac increased (decreased) with an upper (lower) liquid blockage. More liquid entered the unblocked daughter with a blockage in one daughter tube, and this effect was larger with larger gravity effect. A simple theoretical model that predicts Rs and Cac is in qualitative agreement with the experiments over a wide range of parameters.

The Effect of Surface Wettability on Viscous Film Deposition

2009 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Contact Angle ◽  
Film Thickness ◽  
Capillary Number ◽  
High Speed ◽  
Glass Tube ◽  
Contact Angles ◽  
Film Deposition ◽  
Surface Wettability ◽  
Working Fluid ◽  
Uniqueness Of The Solution

The viscous deposition of a liquid film on the inside of a capillary has been experimentally investigated with a focus on the relationship between the film thickness and surface wettability. With distilled water as a working fluid tests were run in a 622 microns diameter glass tube with contact angles of 30° and 105°, respectively. In the first set of experiments the tube was uncoated while in the second set a fluoropolymer coating was applied to increase the contact angle. A film thickness dependence with the contact angle θ (surface wettability) as well as the Capillary number in the form hR ∼ Ca2/3/cosθ is inferred from scaling arguments. For partial wetting it may explain the existence of a thicker film for nonzero contact angle. It was further found that the non-wetting case of 105° contact angle deviates significantly from the existing theories, the film thickness presenting a weak dependence with the Capillary number. This deviation as well as the apparent non-uniqueness of the solution is thought to be caused by the film instability (rupture) observed during the tests. The thickness of the deposited film as a function of the Capillary number was estimated from the liquid mass exiting the capillary and the gas-liquid interface (meniscus) velocity, and compared to Bretherton’s data and a correlation proposed by Quere. The film thickness measurements as well as the meniscus velocity were determined with the aid of a Photron high speed camera with 10000 frames per second sampling capability coupled with a Nikon TE-2000 inverted microscope and a Precisa electronic balance.

scholarly journals Lubrication and frictional analysis of cam–roller follower mechanisms

2017 ◽  
Vol 232 (3) ◽  
pp. 347-363 ◽  
Author(s):  
Shivam S Alakhramsing ◽  
Matthijn de Rooij ◽  
Dirk Jan Schipper ◽  
Mark van Drogen
Keyword(s):  
Film Thickness ◽  
Finite Length ◽  
Power Loss ◽  
Fuel Injection ◽  
Contact Forces ◽  
Injection System ◽  
Maximum Pressure ◽  
Line Contact ◽  
Power Losses ◽  
Minimum Film Thickness

In this work, a full numerical solution to the cam–roller follower-lubricated contact is provided. The general framework of this model is based on a model describing the kinematics, a finite length line contact isothermal-EHL model for the cam–roller contact and a semi-analytical lubrication model for the roller–pin bearing. These models are interlinked via an improved roller–pin friction model. For the numerical study, a cam–roller follower pair, as part of the fuel injection system in Diesel engines, was analyzed. The results, including the evolution of power losses, minimum film thickness and maximum pressures, are compared with analytical solutions corresponding to infinite line contact models. The main findings of this work are that for accurate prediction of crucial performance indicators such as minimum film thickness, maximum pressure and power losses a finite length line contact analysis is necessary due to non-typical EHL characteristics of the pressure and film thickness distributions. Furthermore, due to the high contact forces associated with cam–roller pairs as part of fuel injection units, rolling friction is the dominant power loss contributor as roller slippage appears to be negligible. Finally, the influence of the different roller axial surface profiles on minimum film thickness, maximum pressure and power loss is shown to be significant. In fact, due to larger contact area, the maximum pressure can be reduced and the minimum film thickness can be increased significantly, however, at the cost of higher power losses.

Preparation of Fe2VAl Thermoelectric Module by RF Sputtering

2007 ◽  
Vol 539-543 ◽  
pp. 3285-3289 ◽  
Author(s):  
Akihiro Matsumoto ◽  
Masashi Mikami ◽  
Keizo Kobayashi ◽  
Kimihiro Ozaki ◽  
Toshiyuki Nishio
Keyword(s):  
Film Thickness ◽  
Mechanical Alloying ◽  
Aluminum Content ◽  
Pulse Current ◽  
Rf Sputtering ◽  
Thermoelectric Module ◽  
Electric Force ◽  
Sintering Process ◽  
The One ◽  
Deposited Film

An attempt to prepare Fe2VAl deposited film and the thermoelectric module using RF sputtering has been made. Sputtering target has been prepared using mechanical alloying of metallic powders and the subsequent pulse current sintering process. The obtained deposited film has had a lack of aluminum content compared to the composition of the starting material. Controlling of aluminum content for the preparation of Fe2VAl sputtering target has made it possible to obtain the desired material composition. The film has had the experimental thermoelectric force being similar to the one estimated from the measured thermoelectric data of the materials. Fe2VAl thermoelectric module of eight pairs with a film thickness of 4 μm has had an electric force of 31mV and 5.6μW.

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