Numerical studies on micropart self-alignment using surface tension forces

2008 ◽  
Vol 6 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Cheng Lin ◽  
Fangang Tseng ◽  
Heng-Chuan Kan ◽  
Ching-Chang Chieng
Keyword(s):  
Surface Tension ◽  
Numerical Studies ◽  
Surface Tension Forces

INFLUENCE OF SURFACE TENSION FORCES ON FILMWISE CONDENSATION INTENSITY

2016 ◽  
Vol 7 (1-2) ◽  
pp. 93-102
Author(s):  
Vasily Buz ◽  
Konstantin Goncharov ◽  
Henry F. Smirnov
Keyword(s):  
Surface Tension ◽  
Surface Tension Forces

Effects of surface tension and viscosity on airway reopening

1990 ◽  
Vol 69 (1) ◽  
pp. 74-85 ◽  
Author(s):  
D. P. Gaver ◽  
R. W. Samsel ◽  
J. Solway
Keyword(s):  
Surface Tension ◽  
Fluid Viscosity ◽  
Opening Pressure ◽  
Viscous Forces ◽  
Considerable Portion ◽  
Airway Opening ◽  
Wall Compliance ◽  
Large Opening ◽  
Surface Tension Forces ◽  
The Relationship

We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent “yield pressure” that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.

scholarly journals On the deflection of a liquid jet by an air-cushioning layer

2018 ◽  
Vol 846 ◽  
pp. 711-751 ◽  
Author(s):  
M. R. Moore ◽  
J. P. Whiteley ◽  
J. M. Oliver
Keyword(s):  
Surface Tension ◽  
Equations Of Motion ◽  
Constant Thickness ◽  
Liquid Jet ◽  
Pressure Jump ◽  
Length Scales ◽  
Small Surface ◽  
Numerical Studies ◽  
Impact Problems ◽  
Systematic Derivation

A hierarchy of models is formulated for the deflection of a thin two-dimensional liquid jet as it passes over a thin air-cushioning layer above a rigid flat impermeable substrate. We perform a systematic derivation of the leading-order equations of motion for the jet in the distinguished limit in which the air pressure jump, surface tension and gravity affect the displacement of the centreline of the jet, but not its thickness or velocity. We identify thereby the axial length scales for centreline deflection in regimes in which the air layer is dominated by viscous or inertial effects. The derived length scales and reduced equations aim to expand the suite of tools available for future analyses of the evolution of lamellae and ejecta in impact problems. Assuming that the jet is sufficiently long that tip and entry effects can be neglected, we demonstrate that the centreline of a constant-thickness jet moving with constant axial speed is destabilised by the air layer for sufficiently small surface tension. Expressions for the fastest-growing modes are obtained in both the viscous-dominated air and inertia-dominated air regimes. For a finite-length jet emanating from a nozzle, we show that, in one particular asymptotic limit, the evolution of the jet centreline is akin to the flapping of an unfurling flag above a thin air layer. We discuss the distinguished limit in which tip retraction can be neglected and perform numerical investigations into the resulting model. We show that the cushioning layer causes the jet centreline to bend, leading to rupture of the air layer. We discuss how our toolbox of models can be adapted and utilised in the context of recent experimental and numerical studies of splash dynamics.

Effects of Surface Tension in the Near Field Wave Breaking of Ships

2008 ◽  
Author(s):  
Fabrizio Pistani ◽  
Angelo Olivieri ◽  
Emilio Campana
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Flow Velocity ◽  
Wave Breaking ◽  
Near Field ◽  
Surface Elevation ◽  
Vortical Structures ◽  
High Speeds ◽  
Resistance Curves ◽  
Surface Tension Forces

When model experiments are performed the viscous and surface tension forces are not scaled accordingly. Thus not all of the features of the flow can be satisfactorily reproduced at model scale. A comparative set of experiments for measuring the model resistance, the free surface elevation and the flow velocity in the near field, have been carried out for models of different scales for evaluating the influence of the dimensions in reproducing the complete wave breaking dynamics. The resistance curves of the models show that the scale effect is present both for low and high speeds. Comparison of the averaged surface elevation reveals that the largest model possess already some of the full scale features. The comparison of the flow velocity fields highlights substantial differences among the models in the formation of the vortical structures. The influence of these vortices on the free surface is discussed and a correlation with surface scars is proposed.

On the capillary forces in an idealized soil

1950 ◽  
Vol 40 (1-2) ◽  
pp. 134-142 ◽  
Author(s):  
E. C. Allberry
Keyword(s):  
Surface Tension ◽  
Experimental Method ◽  
Experimental Verification ◽  
Drop Size ◽  
Capillary Forces ◽  
Experimental Measurements ◽  
Small Drop ◽  
Soil Cohesion ◽  
Work Of Separation ◽  
Surface Tension Forces

1. The attraction between spheres, due to surface tension forces, in a lenticular drop between them is calculated for spheres in contact and at increasing separations up to the point of rupture of the drop. Hence the work of separation of the spheres is calculated.2. Experimental measurements confirm the validity of these calculations, down to very small drop sizes, where it is likely that the failure is in the experimental method. As predicted by Fisher, the force decreases with increasing drop size, while the work of separation increases. Since, however, it is shown that the smaller lenticels are more easily ruptured, no discrimination is provided between the differing explanations of Haines and Fisher of measurements made with the Atterberg apparatus for measurement of soil cohesion.An experimental verification of the validity of Fisher's calculation of the pressure deficiency inside the drop is also given.3. It is pointed out that these results depend on the geometry of the system; types of contact other than that of spheres will show different behaviour. Hence generalizations about the behaviour of a real soil, based on an idealized soil of packed spheres, may lead to erroneous conclusions.

scholarly journals The steady propagation of an air finger into a rectangular tube

2008 ◽  
Vol 614 ◽  
pp. 173-195 ◽  
Author(s):  
ALBERTO DE LÓZAR ◽  
ANNE JUEL ◽  
ANDREW L. HAZEL
Keyword(s):  
Surface Tension ◽  
Capillary Number ◽  
Rectangular Cross Section ◽  
Two Dimensional ◽  
Governing Parameter ◽  
Pressure Drops ◽  
Finger Width ◽  
Steady Propagation ◽  
Finger Tip ◽  
Surface Tension Forces

The steady propagation of an air finger into a fluid-filled tube of uniform rectangular cross-section is investigated. This paper is primarily focused on the influence of the aspect ratio, α, on the flow properties, but the effects of a transverse gravitational field are also considered. The three-dimensional interfacial problem is solved numerically using the object-oriented multi-physics finite-element library oomph-lib and the results agree with our previous experimental results (de Lózar et al. Phys. Rev. Lett. vol. 99, 2007, article 234501) to within the ±1% experimental error.At a fixed capillary number Ca (ratio of viscous to surface-tension forces) the pressure drops across the finger tip and relative finger widths decrease with increasing α. The dependence of the wet fraction m (the relative quantity of liquid that remains on the tube walls after the propagation of the finger) is more complicated: m decreases with increasing α for low Ca but it increases with α at high Ca. Our results also indicate that the system is approximately quasi-two-dimensional for α ≥ 8, when we obtain quantitative agreement with McLean & Saffman's two-dimensional model for the relative finger width as a function of the governing parameter 1/B = 12α2Ca. The action of gravity causes an increase in the pressure drops, finger widths and wet fractions at fixed capillary number. In particular, when the Bond number (ratio of gravitational to surface-tension forces) is greater than one the finger lifts off the bottom wall of the tube leading to dramatic increases in the finger width and wet fraction at a given Ca.For α ≥ 3 a previously unobserved flow regime has been identified in which a small recirculation flow is situated in front of the finger tip, shielding it from any contaminants in the flow. In addition, for α ≳ 2 the capillary number, Cac, above which global recirculation flows disappear has been observed to follow the simple empirical law: Cac2/3α = 1.21.

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