scholarly journals Developed liquid film passing a trailing edge under the action of gravity and capillarity

2018 ◽  
Vol 850 ◽  
pp. 924-953 ◽  
Author(s):  
B. Scheichl ◽  
R. I. Bowles ◽  
G. Pasias
Keyword(s):  
Thin Film ◽  
Surface Tension ◽  
Asymptotic Structure ◽  
General Sense ◽  
Trailing Edge ◽  
Choked Flow ◽  
Edge Singularity ◽  
Streamline Curvature ◽  
Free Interaction ◽  
Weak Disturbances

We consider the asymptotic structure of a steady developed viscous thin film passing the sharp trailing edge of a horizontally aligned flat plate under the weak action of gravity acting vertically and surface tension. The surprisingly rich details of the flow in the immediate vicinity of the trailing edge are elucidated both analytically and numerically. As a central innovation, we demonstrate how streamline curvature serves to regularise the edge singularity apparent on larger scales via generic viscous–inviscid interaction. This is shown to be provoked by weak disturbances of accordingly strong exponential downstream growth, which we trace from the virtual origin of the flow towards the trailing edge. They represent a prototype of the precursor to free interaction in the most general sense, which, interestingly, has not attracted due attention previously. Moreover, we delineate how an increased effect of gravity involves marginally choked flow at the edge.

scholarly journals Steady rimming flows with surface tension

2008 ◽  
Vol 597 ◽  
pp. 91-118 ◽  
Author(s):  
E. S. BENILOV ◽  
M. S. BENILOV ◽  
N. KOPTEVA
Keyword(s):  
Thin Film ◽  
Surface Tension ◽  
Viscous Fluid ◽  
Small Parameter ◽  
Outer Region ◽  
Lubrication Approximation ◽  
Steady Flows ◽  
Matched Asymptotics ◽  
Weak Surface ◽  
Rimming Flows

We examine steady flows of a thin film of viscous fluid on the inside of a cylinder with horizontal axis, rotating about this axis. If the amount of fluid in the cylinder is sufficiently small, all of it is entrained by rotation and the film is distributed more or less evenly. For medium amounts, the fluid accumulates on the ‘rising’ side of the cylinder and, for large ones, pools at the cylinder's bottom. The paper examines rimming flows with a pool affected by weak surface tension. Using the lubrication approximation and the method of matched asymptotics, we find a solution describing the pool, the ‘outer’ region, and two transitional regions, one of which includes a variable (depending on the small parameter) number of asymptotic zones.

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.

scholarly journals On the origin of the circular hydraulic jump in a thin liquid film

2018 ◽  
Vol 851 ◽  
Author(s):  
Rajesh K. Bhagat ◽  
N. K. Jha ◽  
P. F. Linden ◽  
D. Ian Wilson
Keyword(s):  
Thin Film ◽  
Surface Tension ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Capillary Waves ◽  
Hydraulic Jumps ◽  
Planar Surface ◽  
Normal Impact ◽  
Viscous Forces

This study explores the formation of circular thin-film hydraulic jumps caused by the normal impact of a jet on an infinite planar surface. For more than a century, it has been believed that all hydraulic jumps are created due to gravity. However, we show that these thin-film hydraulic jumps result from energy loss due to surface tension and viscous forces alone. We show that, at the jump, surface tension and viscous forces balance the momentum in the liquid film and gravity plays no significant role. Experiments show no dependence on the orientation of the surface and a scaling relation balancing viscous forces and surface tension collapses the experimental data. A theoretical analysis shows that the downstream transport of surface energy is the previously neglected critical ingredient in these flows, and that capillary waves play the role of gravity waves in a traditional jump in demarcating the transition from the supercritical to subcritical flow associated with these jumps.

Surface Effects on the Mechanical Behavior of Buckled Thin Film

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Yong Wang ◽  
Xue Feng ◽  
Bingwei Lu ◽  
Gangfeng Wang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Surface Tension ◽  
Mechanical Behavior ◽  
Flexible Electronics ◽  
Geometric Nonlinearity ◽  
Surface Elasticity ◽  
Surface Effects ◽  
Design Strategy ◽  
Piezoelectric Effects

The buckling of thin films with natural nonlinearity can provide a useful tool in many applications. In the present paper, the mechanical properties of controllable buckling of thin films are investigated by accounting for both geometric nonlinearity and surface effects at nanoscale. The effects of surface elasticity and residual surface tension on both static and dynamic behaviors of buckled thin films are discussed based on the surface-layer-based model. The dynamic design strategy for buckled thin films as interconnects in flexible electronics is proposed to avoid resonance in a given noise environment based on the above analysis. Further discussion shows that the thermal and piezoelectric effects on mechanical behavior of buckled thin film are equivalent to that of residual surface tension.

scholarly journals Synthesis, surface tension, optical and dielectric properties of bismuth oxide thin film

2017 ◽  
Vol 35 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Fatma Meydanerİ Tezel ◽  
İ. Afşin Kariper
Keyword(s):  
Thin Film ◽  
Surface Tension ◽  
Dielectric Constant ◽  
Bismuth Oxide ◽  
Optical Transmission ◽  
Optical Band Gap ◽  
Unit Area ◽  
Optical Transmittance ◽  
Contact Angles ◽  
Oxide Thin Film

AbstractBismuth oxide thin film was deposited by chemical bath deposition (CBD) technique onto a glass substrate. The grain size (D), dislocation density (δ) and number of crystallites per unit area (N), i.e. structural properties of the thin film were determined as 16 nm, 39.06× 10–4line/nm2, 31.25 × 10–31/nm2, respectively. Optical transmittance properties of the thin film were investigated by using a UV-Vis spectrophotometer. The optical band gap (Eg) for direct transitions, optical transmission (T %), reflectivity (R %), absorption, refractive index (nr), extinction coefficient (k), dielectric constant (∊) of the thin film were found to be 3.77 eV, 25.23 %, 32.25 %, 0.59, 3.62, 0.04 and 2.80, respectively. The thickness of the film was measured by AFM, and was found to be 128 nm. Contact angles of various liquids on the oxide thin film were determined by Zisman method, and surface tension was calculated to be 31.95 mN/m.

The influence of slot injection/suction on the spreading of a thin film under gravity and surface tension

2009 ◽  
Vol 211 (1-2) ◽  
pp. 61-71 ◽  
Author(s):  
E. Momoniat ◽  
R. Ravindran ◽  
S. Roy
Keyword(s):  
Thin Film ◽  
Surface Tension
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