scholarly journals Surface tension effects on fully developed liquid layer flow over a convex corner

AIP Advances ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 045206
Author(s):  
Ifrah Bhatti ◽  
Saadia Farid ◽  
Saif Ullah ◽  
Samia Riaz ◽  
Maimoona Faryad
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Convex Corner ◽  
Layer Flow

Role of pulmonary surfactant in airway closure: a computational study

1993 ◽  
Vol 75 (3) ◽  
pp. 1323-1333 ◽  
Author(s):  
D. R. Otis ◽  
M. Johnson ◽  
T. J. Pedley ◽  
R. D. Kamm
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Pulmonary Surfactant ◽  
Computational Study ◽  
Surface Shape ◽  
Airway Closure ◽  
Velocity Surface ◽  
The Mean ◽  
Layer Flow

A numerical model that simulates airway closure by liquid bridging during expiration has been developed. The effects of both surfactant and time-varying geometry have been included; the model determines the liquid layer flow resulting from a surface tension (Rayleigh) instability, and the computation traces the film's development to closure, yielding pressure, velocity, surface shape, and surfactant concentration distributions. It is found that surfactant is effective in retarding or eliminating liquid bridging through the reduction of the mean surface tension and the action of surface tension gradients. The former effect is also critical in minimizing the magnitude of the negative pressure in the liquid layer and thus presumably in reducing the tendency for airway compliant collapse.

The standing hydraulic jump: theory, computations and comparisons with experiments

1992 ◽  
Vol 242 ◽  
pp. 145-168 ◽  
Author(s):  
R. I. Bowles ◽  
F. T. Smith
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Hydraulic Jump ◽  
Computational Study ◽  
Boundary Layer Separation ◽  
Quantitative Agreement ◽  
Primary Role ◽  
Viscous Effects ◽  
Free Interaction ◽  
Everyday Context

In this theoretical and computational study of the flow of a liquid layer, under the influence of surface tension and gravity most notably, the nonlinear equations governing an interaction between viscous effects and the effects of surface tension, gravity and streamline curvature for the limit of large Reynolds numbers are derived. The aim is to make a comparison between the predictions of this theory and the experiments of Craiket al.on the axisymmetric hydraulic jump. Such a jump is commonly encountered in the everyday context of the initial filling of a kitchen sink, for example, and it is found in the present work that initially all the effects listed above can play a primary role in practice in the local jump phenomenon. As a first step here, the flow of the layer over a small obstacle is considered. It is seen that as surface tension becomes increasingly significant the upstream influence becomes more wave-like. Second, calculations and analysis of the nonlinear free interaction are presented and show wave-like behaviour upstream, followed downstream by a depth profile not unlike that in the typical hydraulic jump. The effects of gravity dominate those of surface tension downstream. Finally, comparisons are made with the experiments and show fair quantitative agreement, supporting the present proposition that these hydraulic jumps are caused by boundary-layer separation due to a viscous–inviscid interaction forced by downstream boundary conditions on, in this case, a fully developed, high-Froude-number liquid layer.

Reverse Marangoni surfing

2016 ◽  
Vol 811 ◽  
pp. 612-621 ◽  
Author(s):  
Vahid Vandadi ◽  
Saeed Jafari Kang ◽  
Hassan Masoud
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Scalar Fields ◽  
Finite Depth ◽  
Lower Surface ◽  
Temperature Fields ◽  
Spherical Particles ◽  
Surface Tension Gradient ◽  
Oblate Spheroidal ◽  
Active Particles

We theoretically study the surfing motion of chemically and thermally active particles located at a flat liquid–gas interface that sits above a liquid layer of finite depth. The particles’ activity creates and maintains a surface tension gradient resulting in the auto-surfing. It is intuitively perceived that Marangoni surfers propel towards the direction with a higher surface tension. Remarkably, we find that the surfers may propel in the lower surface tension direction depending on their geometry and proximity to the bottom of the liquid layer. In particular, our analytical calculations for Stokes flow and diffusion-dominated scalar fields (i.e. chemical concentration and temperature fields) indicate that spherical particles undergo reverse Marangoni propulsion under confinement whereas disk-shaped surfers always move in the expected direction. We extend our results by proposing an approximate formula for the propulsion speed of oblate spheroidal particles based on the speeds of spheres and disks.

Surface-tension-induced buckling of liquid-lined elastic tubes: a model for pulmonary airway closure

2005 ◽  
Vol 461 (2058) ◽  
pp. 1847-1868 ◽  
Author(s):  
Andrew L Hazel ◽  
Matthias Heil
Keyword(s):  
Surface Tension ◽  
Liquid Layer ◽  
Solid Mechanics ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Compressive Load ◽  
Elastic Tube ◽  
Airway Closure ◽  
Elastic Tubes ◽  
Pulmonary Airway

We use a fully coupled, three-dimensional, finite-element method to study the evolution of the surface-tension-driven instabilities of a liquid layer that lines an elastic tube, a simple model for pulmonary airway closure. The equations of large-displacement shell theory are used to describe the deformations of the tube and are coupled to the Navier–Stokes equations, describing the motion of the liquid. The liquid layer is susceptible to a capillary instability, whereby an initially uniform layer can develop a series of axisymmetric peaks and troughs, analogous to the classical instability that causes liquid jets to break up into droplets. For sufficiently high values of the liquid's surface tension, relative to the bending stiffness of the tube, the additional compressive load induced by the development of the axisymmetric instability can induce non-axisymmetric buckling of the tube wall. Once the tube has buckled, a strong destabilizing feedback between the fluid and solid mechanics leads to an extremely rapid further collapse and occlusion of the gas-conveying core of the tube by the liquid. We find that such occlusion is possible even when the volume of the liquid is too small to form an occluding liquid bridge in the axisymmetric tube.

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